Introduction
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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Index

Air Mass Calculation	6	Fuel Pressure Regulator

1	Camshaft Position Sensor	Fuel Pump

2	Canister Purge Control Solenoid	Fuel Pump Relay

Carbon Canister	Fuel Trim Adjuster

3	CO% Adjustment	7	Idle Air Control Solenoid

Cold Start Injector	Idle Speed (Base)

Dashpot	Idle Switch

Diagnostic Connector	8	Ignition Coil

4	ECM	Ignition Timing

ECM (Alternate Engine) 	9	Intake Air Temp Sensor

ECM Voltage Table	Main Relay

ECM Voltage Table (Alternate Engine) 	Overview

Engine Coolant Temperature Sensor	Oxygen Sensor

Engine Speed & Position Sensors	Power Steering Pressure Switch

Fault Codes	Power Transistor

Fault Code Erasure	Tachometer Test Connector

Fault Code Extraction	Throttle Body

Fault Code Table	Throttle Plate Base Setting

Firing Order	10	Throttle Position Sensor

5	Fuel Injectors	Wiring Diagram

Fuel Pressure	Wiring Diagram (Alternate Engine)

Copyright © 1999

Repco AUTO-TECH

All Rights Reserved

vwaaf1


Throttle Position Sensor


Intake Air Temp Sensor


Ignition Coil


Idle Air Control Solenoid


Fuel Pressure Regulator


Fuel Injectors


ECM


CO% Adjustment


Canister Purge Control Solenoid


Camshaft Position Sensor


Components & Specifications 1
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

Go To: 	INDEX 	Go To:	COMPONENT LOCATION 	Copyright © Repco AUTO-TECH

Air Mass Calculation

Air Mass Calculation is by way of a Manifold Absolute Pressure (MAP) Sensor within the ECM.

A Vacuum Hose is connect to the ECM:

This supplies Manifold Vacuum to the Manifold Absolute Pressure Sensor.

1 	Camshaft Position Sensor

The Camshaft Position Sensor is a Hall Effect Sensor.

It receives its Voltage from the ECM. It is located inside the Distributor Housing.

To Test:

1.	Disconnect the Fuel Injector Connector.

2.	Disconnect the Cold Start Injector Connector.

3.	Slide the Rubber Boot away from the 3 Pin Connector.

4.	Backprobe the back of the Connector.

(May have to remove Connector to do this)

5.	Connect an LED Testlight between the Centre Terminal and the Outside Terminal.

(Brown / White Wire)

6.	Crank the Engine.

The LED should be observed to Flicker.

If no Flickering is observed, suspect that the Camshaft Position Sensor is Faulty

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #11 and 30.	See ECM Pin #37 and 38.

OR

Remove the Connector from the Camshaft Position Sensor

Test the Voltage between Terminals 1 and 3 on the Sensor connector should be:

at least 10 Volts.

(Connector removed from Sensor)

Components & Specifications Cont. >>


Components & Specifications 2
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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2 	Canister Purge Control Solenoid

Located at the Rear of the Engine Compartment near the Heater Hoses.

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #4.	See ECM Pin #26.

To Test

1.	Engine must be at Operating Temperature.

2.	Start Engine and allow to idle.

3.	Remove the Vacuum Hose to the Canister at the Canister Purge Solenoid Valve.

4.	The Valve should not be pulsing and No Vacuum should be evident.

5.	Raise Engine Speed.

6.	Valve Pulsing can be measured (LED Testlight), and Vacuum should be felt.

Carbon Canister

The Carbon Canister is located on the Front Left Wheel Housing.

3 	CO% Adjustment

The CO% can be measured at the CO Tap Tube. (Fitted with a Cap)

This is located in the Engine Bay on the Left Rear of the Intake Manifold.

The CO% should be in the range of 0.3 to 1.2%

The CO% Adjusting Screw (Fuel Trim Adjuster) is located on the side of the Intake Ducting.

Not all Models have CO% adjustment.

To Test:

1.	Remove Cap from Tap Tube and fit Probe.

Ensure that the Probe is sealed into the Tap Tube correctly.

2.	Start Engine, (must be at Operating Temperature) and allow to idle.

3.	Remove the Engine Coolant Temperature Sensor Connector.

If the Engine stalls after removing the Connector:

Re-fit Connector before starting Engine, otherwise the ECM will go into limp home mode.

4.	Measure CO%.

5.	If CO% not to specifications, adjust level to 0.7 ± 0.2 %

6.	Reconnect Engine Coolant Temperature Sensor Connector.

Cold Start Injector

The Cold Start Injector is located on the Inlet Manifold.

The Cold Start Injector operates when the Engine is cranked at low ambient temperature.

The time the Cold Start Injector is open is determined by the ECM.

The ECM uses the Signal from the Coolant Temperature Sensor to determine this.

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #3.	See ECM Pin #5.

Components & Specifications Cont. >>


Components & Specifications 3
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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Dashpot (Manual Transmission Vehicles Only)

The Dashpot is located on the Throttle Linkage near the Throttle Body.

The Dashpot should slow the closing of the Throttle Plate.

Diagnostic Connector

The Diagnostic Connector is located in the Fold Down Relay Plate Cover (Dash).

Data from the ECM can only be accessed using a Data Scanner.

Such as an OTC 4000 Enhanced with VAG Software.

Engine Coolant Temperature Sensor

The Engine Coolant Temperature Sensor is located between #1 & #2 Spark Plugs.

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #14.   	See ECM Pin #11.

Engine Speed & Position Sensors

The Transporter uses a single Camshaft Position Sensor for Engine Speed & Position.

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #11 and 30.   	See ECM Pin #37 and 38.

Firing Order (5 Cylinder)

1 2 4 5 3

Number #1 Cylinder is located on the Drivers Side of the Engine.

Components & Specifications Cont. >>


Components & Specifications 4
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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5 	Fuel Injectors

The Fuel Injectors are press fitted into the Fuel Rail.

To Remove Injectors.

1.	Lock an M6 Socket Head Screw into a Vice, (Threaded end in Vice).

2.	Position Injector over M6 Screw and push downward on the Fuel Rail.

This action will force the Injector upwards and out of the Fuel Rail.

Replace “O” Ring when re-installing.

To Test Resistance:

These Engines share the 2 Pin & 6 Pin Injector Connectors.

To Test:

Fuel Injectors with 6 Pin Connector:

The Fuel Injector Ground may become Open Circuit, as a result the Injectors will not pulse.

If this occurs, replace the Ground Wire between the Battery and the Transmission.

Injector Resistance:

Measured between each Injector and a common ground (#6)

Vehicles built Pre 1995:	Vehicles built from 1995 onwards:

12 to 18 ohms.	15 to 20 ohms.

Fuel Injectors with 2 Pin Connector:

Remove the Connector.

Measure the Resistance of the Injectors across the Two Terminals of the Connector.

The Resistance should be 3.0 to 4.0 Ohms.

The Individual Resistance should be:

15 to 20 Ohms.

Fuel Pressure

Vacuum to Fuel Pressure Regulator.	No Vacuum to Fuel Pressure Regulator.

250 Kpa	300 Kpa

6 	Fuel Pressure Regulator

The Fuel Pressure Regulator is located on the Left Hand End of the Fuel Rail.

(Facing backwards).

Fuel Pump

The Electric Fuel Pump is located inside the Fuel Tank.

Components & Specifications Cont. >>


Components & Specifications 5
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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Fuel Pump Relay

The Fuel Pump Relay is located in the Relay Box .

The Fuel Pump Relay is the Right Hand Relay in the bottom row.

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #7.	See ECM Pin #24.

Fuel Trim Adjuster

The Fuel Trim Adjuster is a Potentiometer with a Sealing Plug.

The Fuel Trim Adjuster is located on the Air Intake Duct.

To Test Voltage:

AAF Engine

See ECM Pin #35.

To Test Resistance:

0 to 2000 ohms

7 	Idle Air Control Solenoid

The Idle Air Control Solenoid is located on top of the Valve Cover.

When the Ignition is ON, the Idle Air Control Solenoid should be felt to vibrate or hum.

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #25.   	See ECM Pin #23.

To Test:

At Idle.	Under Load.

1.	Engine to Operating Temperature.	1.	If the Engine is Cold OR

2.	Idle Switch Contact closed.	2.	If the A/C is on OR

3.	No Engine Load.	3.	If anything Electrical is ON OR

4.	Idle Speed Controller should draw:	4.	If the Power Steering is Under Load OR

500 to 600 Milliamps at Engine Idle.	5.	If the Ignition Timing Incorrect.

The Electrical Load for the Idle Speed Controller will be:

In the 400 to 1000 Milliamps Range

To Test Resistance:

2 to 10 Ohms.

Idle Speed (Base)

The Idle Speed is NOT Adjustable, it can be checked for Correct Specifications Only.

To Check:

1.	Engine to Operating Temperature.

2.	No Engine Load.

3.	Gear Selector in Park (A/T), Neutral (M/T).

The Idle Speed should be 800 ± 25 RPM

If the Engine is started after stalling (Or shutting down under some circumstances),

The Idle Speed could run abnormally high for up to 3 or 4 minutes.

This is a Normal Function.

Components & Specifications Cont. >>


Components & Specifications 6
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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Idle Switch (Where Fitted)

The Idle Switch is located on the Throttle Body, opposite the Throttle Position Switch.

An Independent Switch used to detect that the Throttle Plate is at the closed position.

The Idle Switch contacts should be closed when the Throttle Plate is at its closed position.

If the Switch Contacts do not close, follow this procedure:

1.	Ensure nothing is stopping the Throttle Plate from closing fully (Throttle Cable etc).

2.	Determine if any catching or binding is preventing the Throttle Plate from closing correctly.

3.	With the Throttle Plate in the fully closed position;

Loosen the Retaining Screws on the side of the Idle Switch.

4.	Adjust the Switch so that the Idle Switch contacts are closed, tighten the Retaining Screws.

5.	Open the Throttle Plate slightly, the Switch should audibly be heard to click

(Or backprobe for continuity switching to infinity)

To Test Voltage:

AAF Alternative Engine

See ECM Pin #10.

Components & Specifications Cont. >>


Components & Specifications 7
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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8 	Ignition Coil

The Ignition Coil is located under the Battery Cover.

The Power Transistor is an integral part of the Ignition Coil.

To Test:

1.	Check Ignition Coil Resistance.

Primary Resistance:	Secondary Resistance:	Spark Plug Connector:

0.5 to 0.7 Ohms.	3000 to 4000 Ohms.	4000 to 6000 Ohms

2.	Remove the 3 Pin Connector from the Ignition Coil.

3.	The Voltage at Pins 1 and 3 should be Battery Volts with the Ignition switched to ON.

To Test Triggering:

AAF Engine	AAF Alternate Engine

See ECM Pin #27.	See ECM Pin #6.

1.	Disconnect the Fuel Injector Connector.

2.	Disconnect the Cold Start Injector Connector.

3.	Remove the 3 Pin Connector from the Ignition Coil.

4.	Connect an LED Testlight between Pins 2 and 3

5.	Crank the Engine, the LED Testlight should be observed to flicker.

If it does not flicker, check the Camshaft Position Sensor.

If this Sensor is OK, suspect the ECM.

6.	If the LED Testlight does flicker, reconnect the 3 Pin Connector to the Coil.

Open the cover above the 3 Pin Connector. Connect the LED Testlight to Terminals #15 & #1.

Do not touch the two exposed Terminals during this next test.

7.	Switch the Ignition ON, the LED should illuminate for between 1 and 2 seconds.

8.	Crank the Engine, the LED should be observed to flicker.

9.	If no flickering is observed, the Power Transistor can be suspected of being faulty.

Components & Specifications Cont. >>


Components & Specifications 8
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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Ignition Timing (Base)

1.	Engine to Operating Temperature.

2.	No Engine Load.

3.	Gear Selector in Park (A/T), Neutral (M/T).

4.	Start Engine.

5.	Raise the RPM to 2000-2500RPM.

5.	The Timing should be observed to be 6° ± 2° BTDC

6.	If not to specifications, rotate Distributor to achieve specifications.

9 	Intake Air Temperature Sensor Assembly

The Intake Air Temperature Sensor Assembly is located on the Intake Hose.

(Between the Air Filter and Throttle Body)

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #15. 	 See ECM Pin #30.

To Test Resistance:

Measure the Resistance between the Connector Pins:

Should be 2000 to 3000 Ohms @ 20°C.

1.	Spray Sensor with Commercial Freeze Spray.

2.	Resistance should be observed to change uniformly with Temperature Drop.

Main Relay

The Main Relay is located in the Relay Box.

The Main Relay is the 2nd on the left on the second row from bottom.

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #38.  	See ECM Pin #19.

Overview

These Vehicles are equipped with an Anti Theft Code for the Radio.

Any operation that requires disconnection of the Battery will erase this Code.

These Imported Vehicles are equipped with two different "Digifant" Fuel Injection Systems.

Although the Two Injection Systems are different, they share many common components.

Not all Vehicles have an Engine Checklight.

Oxygen Sensor

The Oxygen Sensor is located in the Front Exhaust Pipe.

Access is from beneath the Vehicle.

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #8. 	See ECM Pin #16.

Components & Specifications Cont. >>


Components & Specifications 9
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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Power Steering Pressure Switch

The Power Steering Pressue Switch is located on the High Pressure Hose near Steering Rack.

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #5.  	See ECM Pin #12.

Power Transistor

The Power Transistor is located under the Battery Cover.

The Power Transistor is an integral part of the Ignition Coil.

Tachometer Test Connector

Connect to Terminal #1 of the Ignition Coil.

Throttle Body

The Throttle Body incorporates:

1. A Throttle Stop Screw

2. An Idle Switch and

3. A Throttle Position Sensor.

Before making any adjustments to the Throttle Body;

1.	Ensure the Throttle Body Bore is clean.

2.	Do not allow any Solvents to enter any Bypass Orifices.

Throttle Plate Base Setting

The Throttle Plate Base Setting is adjusted by the Throttle Stop Screw on the Throttle Body.

The Throttle Stop Screw is Factory Set. It should NOT require adjustment during routine service.

To Adjust:

1.	Wind the Limit Screw outwards.

(Until there is a gap between the Limit Screw and the Throttle Plate Lever)

2.	Ensure the Throttle Plate is not binding, open and close a few times.

3.	With the Throttle Plate at the fully closed position, wind the Limit Screw inwards.

4.	When the Screw just contacts the Throttle Plate Lever:

Wind the Limit Screw in a further ½ turn.

5.	Tighten the Limit Screw Locknut

(Ensure the Limit Screw does not turn when tightening Locknut)

6.	Check the:

Idle Speed.

Throttle Position Sensor.

Dashpot (If fitted)

10 	Throttle Position Sensor

The Throttle Position Sensor is located on the Throttle Body.

Vehicles with Manual Transmissions have a 3 Pin Connector for the TPS.

Vehicles with Automatic Transmissions have a 4 Pin Connector for the TPS.

The 4th Pin is for the Automatic Transmission Computer.

To Test Voltage:

AAF Engine	AAF Alternate Engine

See ECM Pin #1.  	See ECM Pin #34.


Wiring Diagram AAF Engine
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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Wiring Diagram (AAF Engine)

See Key to Wiring Diagram

Key to Wiring Diagram (AAF Engine)

101	Battery	114	Heated Oxygen Sensor

102	Ignition Switch	115	Throttle Position Sensor

103	Starter Motor	116	Tachometer Test Connector (If Fitted)

104	ECM Main Relay	117	Engine Coolant Temperature Sensor

105	Fuel Pump Relay	118	Tachometer Test Connector (If Fitted)

106	Fuse #18 (20 amp)	119	Intake Air Temperature Sensor

107	Fuel Pump Motor	/ Fuel Trim Adjustment Screw

108	Fuel Injectors	(a) Intake Air Temperature Sensor

109	Fuse #15 (10 amp)	(b) Fuel Trim Adjuster

110	Purge Canister Solenoid	120	Tachometer Test Connector (If Fitted)

111	Idle Air Control Solenoid	121	Tachometer

112	Cold Start Injector	122	Camshaft Position Sensor

113	Power Steering Pressure Switch	123	Ignition Coil / Power Transistor

124	EFI Electronic Control Module


Wiring Diagram
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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Wiring Diagram (Alternate AAF Engine)

See Key to Wiring Diagram (Alternate AAF Engine)

Key to Wiring Diagram (Alternate AAF Engine)

101	Battery	114	Heated Oxygen Sensor

102	Ignition Switch	115	Idle Switch

103	Starter Motor	116	Throttle Position Sensor

104	Engine Checklight (Where fitted)	117	Tachometer Test Connector (If Fitted)

105	ECM Main Relay	118	Engine Coolant Temperature Sensor

106	Fuel Pump Relay	119	Tachometer Test Connector (If Fitted)

107	Fuel Injectors	120	Tachometer Test Connector (If Fitted)

108	Fuel Pump Motor	121	Tachometer

109	Fuse #15 (10 amp)	122	Intake Air Temperature Sensor

110	Purge Canister Solenoid	123	Camshaft Position Sensor

111	Idle Air Control Solenoid	124	Ignition Coil / Power Transistor

112	Cold Start Injector 	125	EFI Electronic Control Module

113	Power Steering Pressure Switch


Fault Codes
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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Fault Codes

Fault codes can NOT be extracted manually.

Data from the ECM has to be accessed with a Data Scanner.

Such as an OTC 4000 Enhanced with VAG Software.

Fault Code Erasure

Fault codes can NOT be erased manually.

Data from the ECM has to be erased with a Data Scanner.

Such as an OTC 4000 Enhanced with VAG Software.

Fault Code Extraction

Fault codes can NOT be extracted manually.

Data from the ECM has to be accessed with a Data Scanner.

Such as an OTC 4000 Enhanced with VAG Software.

Fault Code Table

Not all Fault Codes apply to all Vehicles.

The Fault Codes listed in brackets apply to certain Scanners only

Code #	Circuit and Status

1111

(65535)	ECM	Internal Failure

2113

(00515)	Camshaft Position Sensor

 	No Signal

Incorrect Signal

2142

(00524)	Knock Sensor #1

Output Signal out of range.

2144

(00540)	Knock Sensor #2

Output Signal out of range.

2212

(00518) Throttle Position Sensor

Output Signal out of range.

(00703)	Throttle Position Switch

Signal does not conform to Inputs from other Sensors

2222

(00519)	Manifold Absolute Pressure Sensor (Inside ECM)

No signal - check Vacuum Hose

MAP sensor faulty

Throttle Position Sensor faulty

2234

(00532)	Battery Voltage Monitor

Battery Volts above 15.5 Volts

Battery Volts less than 6.1 Volts

2312

(00522)	Engine Coolant Temperature Sensor

Output Signal out of range.

2314

(00545)	EFI ECM to Transmission ECM Data Link

No Signal - open circuit

2322

(00523)	Intake Air Temperature Sensor

Output Signal out of range

2341

(00537)	Oxygen Sensor Control

Control limit is out of range.

2342

(00525)	Heated Oxygen Sensor

Heater Circuit faulty

2411

(00560)	Exhaust Gas Recirculation System

Vacuum Regulator Solenoid Circuit Fault

Vacuum Lines damaged or not connected

EGR Valve Fault

EGR Temperature Sensor Fault

(00758)	Secondary Air Injection System

Circuit Fault

Vacuum Lines faulty or disconnected

Combination Valve stuck

Check Valve stuck

Relay, Solenoid, or Pump faulty

(01087)	ECM Base Setting Incorrect

Base Setting not performed

(Loss of power to ECM)

(01249)	Fuel Injector #1

Injector or Circuit Fault

(01250)	Fuel Injector #2

Injector or Circuit Fault

(01251)	Fuel Injector #3

Injector or Circuit Fault

(01252)	Fuel Injector #4

Injector or Circuit Fault

(01253)	Fuel Injector #5

Injector or Circuit Fault


ECM Voltage Table
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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ECM (AAF Alternate Engine)

Some AAF Engines do not have On Board Diagnostics

For Engine Code AAF	For Engine Code AAC

The ECM has 38 Pins.	The ECM has 68 Pins.

There may be a variation in AAF ECM’s.

See ECM Voltage Specifications AAF Engine.

The Pin Numbers are printed on the ECM Wiring Harness Connector.

The ECM is located in the Engine Bay. (Left Hand Side)

A Vacuum Hose is connect to the ECM:

This supplies Manifold Vacuum to the Manifold Absolute Pressure Sensor. (Within the ECM)

The ECM is Self Testing.

Any Sensors that return inputs that are out of range will cause a Fault Code to be generated.

If the Sensor Range returns to within Specifications, the Fault Code will automatically erased.

When the Vehicle starts, out of range Sensor Signals are written to the Fault Code Memory.

Do not start Vehicle with any Sensors disconnected, or the ECM will go into “Limp Home Mode”.

ECM Voltage Table (AAF Alternate Engine)

The Pin Numbers are printed on the ECM Wiring Harness Connector.

The Specifications listed in the following Table are approximate only.

They may vary between Vehicles.

These measurements should be taken when the Engine is at Operating Temperature.

Pin #	Circuit and Status..........................................	Voltage

1	ECM Ground

Ignition ON / OFF.............................................	0 Volts

2	Fuel Injector Control (Cylinder #4)

Ignition ON......................................................	Battery Volts

Engine Running................................................	Voltage Pulses

5	Cold Start Injector

Ignition ON......................................................	Battery Volts

While Cranking................................................	Low Volts

4	Engine Checklight

Ignition ON / Engine Running

Engine Checklight ON......................................	Low Volts

Engine Checklight OFF.....................................	Battery Volts

5	Cold Start Injector

Ignition ON......................................................	Battery Volts

Initial 14 Seconds (Engine Coolant Cold)............	Low Volts

6	Power Transistor Control

Engine Running................................................	Voltage Pulses

7	ECM Supply Voltage

Ignition ON......................................................	Battery Volts

Via Main Relay (Not switched supply)

9	ECM Ground

Ignition ON / OFF.............................................	0 Volts

10	Idle Switch

Ignition ON

Throttle Plate fully closed

(Switch contacts CLOSED)...............................	Low Volts

Throttle Plate moved from fully closed position....	5 or 12 Volts*

Idle Switch when OPEN will be 5 Volts or 12 Volts depending on Vehicle Build

11	Engine Coolant Temperature Sensor

Ignition ON

Voltage varies with Coolant Temperature............	0.2 to 4.6 Volts

12	Power Steering Pressure Switch

Ignition ON / Engine Running

Steering Wheel at rest (Centred)........................	0 Volts

Steering Wheel moved from rest........................	Battery Volts

14	Transmission Control Module

No Specifications Available...............................	N/A

16	Heated Oxygen Sensor Output

Engine in good Operating Condition;

Hold Engine Speed steady around 2000 RPM.

Voltage Switching should be observed around.....	0.5 Volts

17	Onboard Diagnostic Connector Terminal #1

 	No Specifications Available...............................	N/A

18	Tachometer Signal

Engine Running................................................	Tacho Signal

19	ECM Voltage Supply (Via Main Relay)

  	Ignition ON

Main Relay Energised.......................................	Battery Volts

20	Fuel Injector Control (Cylinder #1)

Ignition ON......................................................	Battery Volts

Engine Running................................................	Voltage Pulses

21	Fuel Injector Control (Cylinder #2)

Ignition ON......................................................	Battery Volts

Engine Running................................................	Voltage Pulses

22	Fuel Injector Control (Cylinder #5)

Ignition ON......................................................	Battery Volts

Engine Running................................................	Voltage Pulses

23	Idle Air Control Solenoid

Ignition ON......................................................	Battery Volts

Engine Running................................................	Voltage Pulses

24	Fuel Pump Relay Control

Engine Running................................................	Low Volts

25	Cranking Signal

Engine Cranking...............................................	> 8 Volts

26	Purge Canister Solenoid Control

Ignition ON......................................................	Battery Volts

Engine Running,

Solenoid Energised (Duty cycle)........................	Lower Volts

28	Sensor Ground

Ignition ON / OFF.............................................	0 Volts

30	Intake Air Temperature Sensor

Ignition ON

Voltage varies with Intake Air Temperature..........	0.2 to 4.6 Volts

31	ECM Supply Voltage (Via Fuse #15)

Ignition ON......................................................	Battery Volts

32	Air Conditioner System

No Specifications Available...............................	N/A

33	Throttle Position Sensor Supply Voltage

Ignition ON......................................................	5 Volts

34	Throttle Position Sensor Output

Ignition ON

Throttle Plate closed to fully open......................	0.3 to 5.0 Volts

35	ECM Ground

Ignition ON / OFF.............................................	0 Volts

36	Onboard Diagnostic Connector Terminal #2

No Specifications Available...............................	N/A

36	Onboard Diagnostic Connector Terminal #2

No Specifications Available...............................	N/A

37	Camshaft Position Sensor Output

Engine Running................................................	Voltage Pulses

38	Camshaft Position Sensor Supply Voltage

Ignition ON......................................................	> 10 Volts


ECM Voltage Table AAF Engine
VOLKSWAGEN TRANSPORTER 2.5L (AAF Engine) 1992 to 1995 Engine Management System

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4 	ECM (AAF Engine)

Some AAF Engines do not have on Board Diagnostics

For Engine Code AAF the ECM has 38 Pins.

There may be a variation in AAF ECM’s.

See ECM Voltage Specifications AAF Alternate Engine.

The Pin Numbers are printed on the ECM Wiring Harness Connector.

The ECM is located in the Engine Bay. (Left hand side)

A Vacuum Hose is connect to the ECM:

This supplies Manifold Vacuum to the Manifold Absolute Pressure Sensor. (Within the ECM)

The ECM is Self Testing.

Any Sensors that return inputs that are out of range will cause a Fault Code to be generated.

If the Sensor Range returns to within Specifications, the Fault Code will automatically erased.

When the Vehicle starts, out of range Sensor Signals are written to the Fault Code memory.

Do not start Vehicle with any Sensors disconnected. (The ECM will go into “Limp Home Mode”)

ECM Voltage Table (AAF Engine)

The Pin Numbers are printed on the ECM Wiring Harness Connector.

The Specifications listed in the following table are approximate only.

They may vary between Vehicles.

Unless otherwise stated, measurements are taken when the Engine is at operating temperature.

Pin #	Circuit and Status..........................................	Voltage

1	Throttle Position Sensor Output

Ignition ON

Throttle Plate Closed to fully Open.....................	0.3 to 5.0 Volts

2	Fuel Injector Control Circuit

Ignition ON

 	Main Relay Energised......................................	Battery Volts

3	Cold Start Injector

Ignition ON......................................................	Battery Volts

While Cranking................................................	Low Volts

4	Canister Purge Solenoid Control

Ignition ON......................................................	Battery Volts

Engine Running,

Solenoid Energised (Duty Cycle).......................	Lower Volts

5	Power Steering Pressure Switch

Ignition ON / Engine running

Steering Wheel at rest (Centred).......................	0 Volts

Steering Wheel moved from rest........................	Battery Volts

7	Fuel Pump Relay Control

Engine Running...............................................	Low Volts

8	Heated Oxygen Sensor Output

Engine in good operating condition;

Hold Engine Speed steady around 2000 RPM.

Voltage Switching should be observed...............	around 0.5 Volts

10	Tachometer Signal

Engine Running...............................................	Tacho Signal

11	Camshaft Position Sensor Output

Engine Running...............................................	Voltage Pulses

12	Throttle Position Sensor Supply Voltage

  	Ignition ON......................................................	5 Volts

13	Sensor Ground

Ignition ON / OFF.............................................	0 Volts

14	Engine Coolant Temperature Sensor

Ignition ON

Voltage varies with Coolant Temperature............	0.2 to 4.6 Volts

15	Intake Air Temperature Sensor

 	Ignition ON

Voltage varies with Intake Air Temperature.........	0.2 to 4.6 Volts

20	ECM Ground

Ignition ON / OFF.............................................	0 Volts

25	Idle Air Control Solenoid

Ignition ON......................................................	Battery Volts

Engine Running...............................................	Voltage Pulses

26	Cranking Signal

Engine Cranking..............................................	> 8 Volts

27	Power Transistor Control

Engine Running...............................................	Voltage Pulses

29	ECM Ground

Ignition ON / OFF.............................................	0 Volts

30	Camshaft Position Sensor Supply Voltage

 	Ignition ON......................................................	> 10 Volts

31	(A/T) Transmission Control Module

No Specifications Available...............................	N/A

32	Onboard Diagnostic Connector Terminal #2

No Specifications Available...............................	N/A

33	ECM Ground

Ignition ON / OFF.............................................	0 Volts

35	Fuel Trim Adjuster (Intake air assembly)

Ignition ON

Voltage varies with Fuel Trim Adjustment...........	N/A

36	ECM Supply Voltage

Ignition ON......................................................	Battery Volts

Via Main Relay (Not Switched Supply)

37	Air Conditioner System

No Specifications Available...............................	N/A

38	ECM Voltage Supply (Via Main Relay)

Ignition ON

 	Main Relay Energised......................................	Battery Volts