INDEX
VOLKSWAGEN TRANSPORTER 2.5L (ACU Engine) 1992 to 1998 Engine Management System

Go To:	Individual Component	Full Topic

Air Injection	Components and Specifications

Air Mass Calculation	ECM Voltage Specifications

Camshaft Position Sensor 	Engine Speed & Position Sensors

Dashpot 	Exhaust Gas Recirculation System

Diagnostic Connector 	Emission Controls

ECM 	Fault Code Procedures

ECM Voltage Table 	Fuel Control

EGR Temperature Sensor 	Idle Speed Control

EGR Vacuum Regulator Solenoid 	Ignition System

Engine Coolant Temperature Sensor 	Wiring Diagram

Exhaust Gas Recirculation Valve

Fault Codes

Fault Code Erasure

Fault Code Extraction

Fault Code Table

Firing Order

Fuel Injectors

Fuel Injector Resistance

Fuel Pressure

Fuel Pressure Regulator

Fuel Pump

Fuel Pump Relay

Idle Speed (Base)

Idle Speed Controller

Idle Switch

Ignition Coil

Ignition Timing

Intake Air Temperature Sensor

Knock Sensors

  	Overview

Oxygen Sensor

Power Transistor

Purge Control Solenoid

Relay (Main)

Throttle Body

Throttle Plate Base Setting

Throttle Position Sensor

Wiring Diagram

Copyright © 1998

Repco AUTO-TECH

All Rights Reserved

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Idle Speed Control
VOLKSWAGEN TRANSPORTER 2.5L (ACU Engine) 1992 to 1998 Engine Management System

Current Topic:	Idle Speed Control

Return To:	INDEX 	Copyright © Repco AUTO-TECH

Throttle Position Sensor:

Vehicles with manual transmissions have a 3 pin connector for the TPS.

Vehicles with automatic transmissions have a 4 pin connector.

The additional pin is for the automatic transmission ECM.

To Test:

See ECM Pin # 41.

Idle Switch (Where Fitted):

Located on the throttle body, opposite the Throttle Position Switch.

The Idle Switch is an independent switch 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:

See ECM Pin # 18.

Idle Speed (Base):

1.	Engine to operating temperature.

2.	No engine load.

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

The idle speed is non adjustable, it can only be checked for correct specification:

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.

Idle Speed Controller:

When the ignition is ON, the idle speed controller should be felt to vibrate or hum.

To Test:

See ECM Pin # 30.

or:

At Idle.

1.	Engine to operating temperature.

2.	Idle Switch Contact closed.

3.	No engine load.

4.	Idle speed controller should draw:

500 to 600 milliamps at engine idle.

or:

Under Load.

1.	If the engine is cold.

2.	A/C on.

3.	Anything electrical ON.

4.	Power steering under load.

5.	Ignition timing incorrect.

The electrical load for the idle speed controller will be:

In the 400 to 1000 mA range

or:

Measure Resistance:

2 to 10 ohms.

Throttle Body:

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 stop screw is factory set and 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)


ECM Voltage Specifications
VOLKSWAGEN TRANSPORTER 2.5L (ACU Engine) 1992 to 1998 Engine Management System

Current Topic:	ECM Voltage Specifications

Return To:	INDEX 	Copyright © Repco AUTO-TECH

ECM:

For engine code ACU the ECM has 68 pins.

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.

The pin numbers are printed on the ECM wiring harness connector.

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.

Sensor signals that are out of range when the vehicle starts will be written to the fault code memory.

Do not start vehicle with any sensors are disconnected, or the ECM will go into “Limp Home Mode”.

ECM Voltage Table:

The specifications listed in the following table are approximate only, and may vary between vehicles.

Unless otherwise stated, the measurements should be taken when the engine is at operating temperature.

ECM Connector:

The pin numbers are printed on the ECM wiring harness connector.

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

1	ECM Ground

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

2	Fuel Injector Control (Cylinder #1)

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

Engine running................................................	Voltage pulses

5	Engine Checklight

Ignition ON

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

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

7	Power Transistor Control

Engine running................................................	Voltage pulses

8	ECM Voltage Supply (Via main relay - unswitched)

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

See Wiring Diagram for origin of supply Voltage

9 	Knock Sensor #1 Ground

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

10	Knock Sensor # 2

Engine running

Connect test equipment between:

Pin #10 and pin #25.........................................	Voltage pulses whilst

 	tapping the engine block.

12	Engine Coolant Temperature Sensor

Ignition ON

Full range of engine coolant temperature............	0.2 to 4.8 Volts

15	Transmission Control Module

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

17	Heated Oxygen Sensor Output

Engine in good operating condition;

Hold engine speed steady around 2000 rpm.

Voltage switching should be observed around.....	0.5 Volt

18	Idle Switch

  	Ignition ON

Throttle plate at CLOSED position.....................	Low Volts

Throttle plate moved from closed position...........	5 Volts

Voltage when throttle plate moved from closed position may be:

12 Volts on some vehicle builds

19	Tachometer Signal

 	Engine running................................................	Tacho signal

20	Oxygen Sensor Heater Control

Engine running

Exhaust gas < 350° C......................................	Low Volts

Exhaust gas > 350° C......................................	Battery Volts

Exhaust gas temperature is approximate

21	ECM Ground

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

23	ECM Voltage Supply (Switched via main relay)

Ignition ON

Main relay energised........................................	Battery Volts

24	Knock Sensor #2 Ground

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

25	Knock Sensor # 2

Engine running;

Connect test equipment between pins;

#25 and pin #10...............................................	Voltage pulses whilst

 	tapping the engine block.

28	Diagnostic Connector

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

29	Secondary Air Injection Relay Control

Engine running

Relay energised..............................................	Low Volts

Relay NOT energised......................................	Battery Volts

30	Idle Air Control Solenoid

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

Engine running................................................	Voltage pulses

31	Fuel Pump Relay Control

Engine running

Fuel pump relay energised................................	Low Volts

32	Cranking Signal

 	Engine cranking...............................................	> 8 Volts

33	Purge Control Solenoid

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

Engine running Solenoid energised (Duty cycle).	Low Volt pulses

34	Knock Sensor # 1

Engine running;

Connect test equipment between pins;

#34 and pin #36...............................................	Voltage pulses whilst

 	tapping the engine block.

35	Sensor Ground

Ignition ON / OFF / Engine running....................	Low Voltage

36	Knock Sensor # 1

Engine running;

Connect test equipment between pins;

#36 and pin #34...............................................	Voltage pulses whilst

 	tapping the engine block.

37	Intake Air Temperature Sensor

Ignition ON

Full intake air temperature range.......................	0.2 to 4.8 Volts

38	ECM Supply Voltage

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

39	Air Conditioner System

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

40	Throttle Position Sensor Supply Voltage

Ignition ON......................................................	4.5 to 5.0 Volts

41	Throttle Position Sensor Output

 	Ignition ON

Throttle plate at rest (CLOSED).........................	0.3 to 1.7 Volts

Throttle plate fully OPEN..................................	3.0 to 5.0 Volts

42	ECM Ground

Ignition ON / OFF / Engine running....................	0 Volts

43	Diagnostic Connector

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

44	Camshaft Position Sensor Output

Engine running................................................	Voltage pulses

45	Camshaft Position Sensor Supply Voltage

Ignition ON......................................................	At least 10 Volts

46	Fuel Injector Control (Cylinder #2)

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

Engine running................................................	Voltage pulses

47	Fuel Injector Control (Cylinder #3)

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

Engine runnin..................................................	Voltage pulses

48	Fuel Injector Control (Cylinder #4)

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

Engine running................................................	Voltage pulses

 49	Fuel Injector Control (Cylinder #5)

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

Engine running................................................	Voltage pulses

52	EGR Temperature Sensor

Engine running

Full range of exhaust gas temperature...............	0.2 to 4.8 Volts

Not all vehicles

67	EGR Vacuum Regulator Solenoid

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

Solenoid energised..........................................	Low Volts


Exhaust Gas Recirculation System
VOLKSWAGEN TRANSPORTER 2.5L (ACU Engine) 1992 to 1998 Engine Management System

Current Topic:	Exhaust Gas Recirculation System

Return To:	INDEX 	Copyright © Repco AUTO-TECH

Exhaust Gas Recirculation System:

The Exhaust Gas Recirculation System contains:

1.	An Exhaust Gas Recirculation Valve (EGR Valve):

2.	An EGR Temperature Sensor:

3.	An EGR Vacuum Regulator Solenoid:

Exhaust Gas Recirculation Valve (EGR Valve):

See Exhaust Gas Recirculation System.

Located in the left hand rear of the engine bay.

The EGR Valve recirculates exhaust gas into the engine to reduce combustion temperatures.

To Test:

1.	Apply vacuum to the EGR Valve.

2.	The Idle should deteriorate.

3.	Warm engine.

4.	Raise engine speed to:

1800rpm

5.	EGR Valve should begin to open.

EGR Temperature Sensor:

See Exhaust Gas Recirculation System.

Attached to the EGR Valve.

The EGR Temperature Sensor is a negative temperature coefficient sensor.

This sensor sends a signal to the ECM and is used to detect a blocked EGR Valve.

(Low Temperature = Blocked System)

To Test:

See ECM Pin # 52.

EGR Vacuum Regulator Solenoid:

See Exhaust Gas Recirculation System.

Located on the vacuum line of the EGR Valve.

The EGR Vacuum Regulator Solenoid controls the vacuum supply to the EGR Valve.

Vacuum should be allowed to the EGR Valve:

1.	When the engine is warm.

2.	And cruising over 1800rpm

To Test:

See ECM Pin # 67.

or:

Resistance:

27 to 31 ohms


Emission Controls
VOLKSWAGEN TRANSPORTER 2.5L (ACU Engine) 1992 to 1998 Engine Management System

Current Topic:	Emission Controls

Return To:	INDEX 	Copyright © Repco AUTO-TECH

Air Injection (Where Fitted):

Air is injected in behind the exhaust valves for 97 seconds when the engine is started cold.

(15 to 35° C)

Also when the coolant temperature is below 60°C.

This will produce oxygen rich exhaust which aids in fast catalytic converter warm up.

The ECM controls the Air Injection Solenoid valve.

Power is supplied to the:

1.	Air Injection Valve.

2.	An electric Air Pump.

Via relay J299.

To Test:

See ECM Pin # 29.

Dashpot:

Located on the throttle body linkage.

The Dashpot should slow the closing of the throttle plate under deceleration.

Fitted to manual transmission vehicles only.

Oxygen Sensor:

To Test:

See ECM Pin # 17.

Purge Control Solenoid:

Located near the front left wheel housing.

To Test:

See ECM Pin # 33.

1.	Engine must be at operating temperature.

2.	Start engine and allow to idle.

3.	Remove the vacuum hose from the purge canister 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.


Ignition System
VOLKSWAGEN TRANSPORTER 2.5L (ACU Engine) 1992 to 1998 Engine Management System

Current Topic:	Ignition System

Return To:	INDEX 	Copyright © Repco AUTO-TECH

Power Transistor / Ignition Coil:

Located under the battery cover.

The power transistor is an integral part of the ignition coil.

To Test:

1.	Check coil resistance.

Primary resistance:

0.5 to 0.7 ohm.

Secondary resistance:

3000 to 4000 ohms.

Spark Plug Connector:

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:

See also ECM Pin # 7.

or:

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 small cover above the 3 pin connector and connect the LED testlight to these two terminals:

#15 and #1.

Caution! 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.

Firing Order:

Number #1 cylinder is on the drivers side.

1 2 4 5 3 (5 cylinder)

Ignition Timing

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 engine rpm to:

2000-2500 rpm

6.	The timing should be observed to be:

6 ± 2° BTDC

7.	If not to specifications, rotate distributor to achieve:

6 ± 1° BTDC

Knock Sensors:

Located on the engine block.

To Test:

Knock Sensor # 1.

See ECM Pin # 34 & #36.

Knock Sensor # 2.

See ECM Pin # 10 & # 25.

1.	Connect timing light.

2.	Start engine and allow to run.

3.	Tap block in vicinity of knock sensors individually.

Do not strike sensor

4.	The timing should be visibly affected by the knocking.


Engine Speed & Positon Sensors
VOLKSWAGEN TRANSPORTER 2.5L (ACU Engine) 1992 to 1998 Engine Management System

Current Topic:	Engine Speed & Position Sensors

Return To:	INDEX 	Copyright © Repco AUTO-TECH

Engine Speed & Position Sensors:

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

Camshaft Position Sensor:

The Camshaft Position Sensor is a Hall Effect Sensor.

It is located inside the distributor housing.

The camshaft position sensor receives its voltage from the ECM.

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

or:

The Voltage between terminals:

1 and 3 on the camshaft position sensor connector should be:

at least 10 Volts.

(Connector removed from sensor)

or:

See ECM Pin # 44.


Components and Specifications
VOLKSWAGEN TRANSPORTER 2.5L (ACU Engine) 1992 to 1998 Engine Management System

Current Topic:	Components and Specifications

Return To:	INDEX 	Copyright © Repco AUTO-TECH

Overview:

This vehicle is equipped with an anti theft code for the radio.

Any operation that requires disconnecting the battery will erase this code.

These imported vehicles are equipped with Digifant fuel injection systems.

Not all vehicles have an engine checklight.

Air Mass Calculation

The Transporter uses an MAP Sensor.

This is located in the ECM.

Diagnostic Connector

Vehicles built before (Generally)12 / 95 - fold down relay plate cover (Dash);

Vehicles built from 01 / 96 - Unclip the cover on the dash (Next to the instrument cluster)

Engine Coolant Temperature Sensor:

Located between #1 & #2 spark plugs .

To Test:

See ECM Pin # 12.

Intake Air Temperature Sensor:

Located on the intake hose.

(Between the air filter and throttle body)

This assembly may also contains a CO% adjusting screw.

(Not all models)

 To Test:

See ECM Pin # 37.

or:

Measure the resistance between the connector pins:

1.	Spray sensor with commercial freeze spray.

2.	Resistance should be observed to change uniformly with temperature drop.

or:

Measure Resistance:

2000-3000 ohms @ 20°C

Main Relay

Located in the relay box.

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

To Test:

See ECM Pin # 8.


Fuel Control
VOLKSWAGEN TRANSPORTER 2.5L (ACU Engine) 1992 to 1998 Engine Management System

Current Topic:	Fuel Control

Return To:	INDEX 	Copyright © Repco AUTO-TECH

Fuel Pump

The electric fuel pump is located inside the fuel tank.

Fuel Pressure

250 kpa with vacuum to fuel pressure regulator.

300 kpa without vacuum to fuel pressure regulator.

Fuel Pressure Regulator:

Located on the left hand end of the fuel rail. (Facing backwards)

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.

Fuel Injector Resistance:

This engine shares a 2 pin & 6 pin injector connector.

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.

Fuel Injectors with 6 Pin Connector:

Measure between each injector terminal and a common ground. (#6)

Vehicles built Pre 1995:

12 to 18 ohms.

Vehicles built from 1995 onwards:

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 Pump Relay

Located in the relay box.

The Fuel Pump Relay id the right hand relay in the bottom row.

To Test:

See ECM Pin # 31.


Wiring Diagram
VOLKSWAGEN TRANSPORTER 2.5L (ACU Engine) 1992 to 1998 Engine Management System

Current Topic:	Wiring Diagram

Return To:	INDEX 	Copyright © Repco AUTO-TECH

See Key to Wiring Diagram (ACU Engine)

Wiring Diagram (ACU Engine):

Key to Wiring Diagram (ACU Engine):

101	Battery

102	Ignition Switch

103	Starter Motor

104	Engine Checklight

105	EFI Main Relay

106	Fuel Injectors

107	Fuel Pump Relay

108	Fuse 15 (10 amp)

109	Fuse 18 (20 amp)

110	Fuel Pump Motor

111	Purge Canister Solenoid Valve

112	Idle Air Control Solenoid Valve

113	EGR Vacuum Regulator Solenoid Valve

114	Heated Oxygen Sensor

115	Secondary Air Solenoid Valve

116	Secondary Air Pump Motor

117	Secondary Air Relay

118	Knock Sensor #2

119	Knock Sensor #1

120	Diagnostic Connector

121	EGR Temperature Sensor

122	Throttle Position Sensor

123	Idle Position Switch

124	Engine Coolant Temperature Sensor

125	Tachometer Test Connector

126	Tachometer Test Connector

127	Tachometer Test Connector

128	Intake Air Temperature Sensor

129	Tachometer

130	Camshaft Position Sensor

131	Ignition Coil / Power Transistor

132	EFI Electronic Control Module


Fault Codes
VOLKSWAGEN TRANSPORTER 2.5L (ACU Engine) 1992 to 1998 Engine Management System

Current Topic:	Fault Code Procedures

Return To:	INDEX 	Copyright © Repco AUTO-TECH

Fault Codes

Fault codes cannot be extracted manually.

Data from the ECM has to be accessed with a data scanner.

Such as the OTC 4000 enhanced, with VAG Software.

Fault Code Extraction:

Not applicable

Fault Code Erasure:

Data Scanner

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

Numbers in brackets indicate the use of Vag or OTC 4000 Enhanced software.

1111

(65535)	ECM	Internal Failure

2113

(00515)	Camshaft Position Sensor

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 (Only applies after replacing the 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