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Home >> Volkswagen >> 1998 >> Passat Wagon (3B5) L4-1.8L Turbo (AEB) >> Repair and Diagnosis >> Powertrain Management >> Fuel Delivery and Air Induction >> Throttle Body >> Testing and Inspection

Throttle Body: Testing and Inspection



NOTE: If the Throttle Body Control Module is replaced, the new assembly MUST BE matched to the Engine Control Module. See "Matching Engine Control Module to Throttle Body Control Module" at Service and Repair.

Special tools, testers, measuring instruments and auxiliary items required:
- VAG 1551/1552 Scan Tool with VAG 1551/3 adaptor cable
- VAG 1598/22 Test Box
- Fluke 83 Multimeter
- VW 1594 Adaptor kit
- Wiring diagram

Function Notes:
- Components of Throttle Body Control Module J338: Throttle body drive G186, throttle body drive angle sensor G187, Throttle Position sensor G69 and Closed Throttle switch F60
- All settings are made using VAG 1551 Scan Tool in Function 04
- If the complete Throttle Body Control Module has no current (e.g connector disconnected) the throttle valve moves to a predetermined mechanically determined position which will increase idle speed to 1200 - 1300 rpm when engine is at normal operating temperature.
- If no current reaches the Throttle Body Drive G186, the throttle will move to the mechanically predetermined position (emergency running gap), but because the Closed Throttle Position sensor idle speed switch F60 is still recognized an almost normal idling speed of approx. 900 rpm is achieved by relatively retarding the ignition
- If the Engine Control Module recognizes a DTC for the Throttle Body Drive angle sensor G187 the Throttle Body Drive G186 is switched to receive no current by the Engine Control Module and the throttle moves again to the mechanically predetermined position (emergency running gap).

Closed Throttle Position switch F60:
- Connect VAG 1551/1552 Scan Tool
- Switch ON ignition
- Press 0 and 1 buttons to select "Address word" 01
"Engine electronics"

Display will appear as shown

Rapid data transfer HELP
Select function XX

- Press 0 and 8 buttons to select Function 08:
"Read measuring value block"
- Press Q button to enter input

Display will appear as shown

Read measuring value block HELP
Input display group number XXX

- Press 0,0 and 5 buttons to select "Display number 5"
- Press Q button to enter input

Display will appear as shown (1 to 4 = Display zones)

Read measuring value block 5 ->
1 2 3 4

- Check the Closed Throttle Position switch (Display zone 4)






- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input

Continuation of check when Display shows partly open throttle





- Disconnect 8 pin harness connector from Throttle Body Control Module.
- Bridge connector terminals 3 + 7 using jumper wires from VW 1594 and observe display.

If display shows idling:
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.
- Replace Throttle Body Control Module J338.

If display shows Partially Open Throttle:
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.
- Check Voltage supply of Throttle Body Control Module and wiring to Control Module. See below in article.

If Voltage supply and wiring OK:
- Replace Engine Control Module

Continuation when display constantly shows idling
- Disconnect 8-pin harness connector from Throttle Body Control Module.

If Display shows Partially Open Throttle:
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.
- Replace Throttle Body Control Module J338.

If Display shows idling:
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.
- Check Throttle Body Control Module Voltage supply and wiring to the Control Module as described below.

If Voltage supply and wiring OK:
- Replace Engine Control Module

Throttle Body Drive G186 and Throttle Body Drive Angle Sensor G187, Checking

Test conditions:
- Engine Coolant Temperature at least 85 °C.

Test sequence:
- Connect VAG 1551/1552 Scan Tool
- Start engine and let idle
- Press 0 and 1 buttons to select "Address word" 01
"Engine electronics"

Display will appear as shown

Rapid data transfer HELP
Select function XX

- Press 0 and 8 buttons to select Function 08:
"Read measuring value block"
- Press Q button to enter input

Display will appear as shown

Read measuring value block HELP
Input display group number XXX

- Press 0, 5 and 5 buttons to select "Display group 55"
- Press Q button to enter input

Display will appear as shown (1 to 4 = Display zones)

Read measuring value block 55 ->
1 2 3 4

- Check idle speed control specifications (Display zones 1 to 4)





If specification not obtained:
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.





- Disconnect 8-pin harness connector to Throttle Body Control Module.
- Switch Fluke 83 Multimeter to resistance range
- Measure throttle valve positioner resistance between connector terminals 1 + 2.
- Specification: 3 to 200 Ohms
- Check Throttle Body Control Module Voltages supply and wiring to Control Module as described below.

If NO malfunction detected:
- Replace Throttle Body Control Module J338.





Evaluating Disply group 55





Significance of 4 position Display

Throttle Position Sensor G69, Checking

Test conditions:
- Coolant temperature at least 85 °C.

Test sequence
- Connect VAG 1551/1552 Scan Tool
- Switch ON ignition
- Press 0 and 1 buttons to select "Address word" 01
"Engine electronics"

Display will appear as shown

Rapid data transfer HELP
Select function XX

- Press 0 and 8 buttons to select Function 08:
"Read measuring value block"
- Press Q button to enter input

Display will appear as shown

Read measuring value block HELP
Input display group number XXX

- Press 0, 0 and 3 buttons to select "Display group 3"
- Press Q button to enter input

Display will appear as shown (1 to 4 = Display zones)

Read measuring value block 3 ->
1 2 3 4

- Read off throttle valve angle in Display zone 3.





- Slowly but fully open throttle, observe angle in Display zone 3
- Value must increase uniformly over the complete range.
- Press the -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.

NOTE: The displayed value is dependent on the tolerances of the Throttle Position sensor and does not correspond to the actual opening angle.

If the value does not increase uniformly:
- Replace Throttle Body Control Module J338.

If the display constantly shows 0 <° or is above 90 <°





Continuation of check when display 0 <°:





- Disconnect 8-pin harness connector to Throttle Body Control Module.
- Bridge harness connector terminals 5 + 7 using jumper wires from VW 1594 adaptor kit and observe display.

If display is above 90 <°:
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.
- Replace Throttle Body Control Module J338.

If Display is 0 <°:
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.
- Check Throttle Body Control Module Voltage supply and wiring to Control Module See below.

Voltage supply and wiring OK:"
- Replace Engine Control Module

Continuation of check when Display is above 90 <°:
- Disconnect 8-pin harness connector to Throttle Body Control Module.

If Display is 0 <°:
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.
- Replace Throttle Body Control Module J338.

If display is above 90 <°:
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.
- Check Throttle Body Control Module Voltage supply and wiring to Control Module. See below.

If Voltage supply and wiring OK:
- Replace Engine Control Module

Voltage Supply And Wiring To Control Module, Checking:
- Disconnect 8-pin harness connector to Throttle Body Control Module.
- Switch Multimeter to Voltage range
- Connect Multimeter between connector terminals 4 + 7.
- Switch ON ignition.
- Specification: 4.5 Volts minimum
- Switch OFF ignition.
- Connect Multimeter between connector terminals 3 + 7.
- Switch ON ignition.
- Specification: 9 Volts minimum
- Switch OFF ignition.





- Connect VAG 1598/22 Test Box to Engine Control Module harness connector.





- Check wiring for open circuit between Test Box and harness connector using Wiring diagram.
Terminal 1 + socket 66
Terminal 2 + socket 59
Terminal 3 + socket 69
Terminal 4 + socket 62
Terminal 5 + socket 75
Terminal 7 + socket 67
Terminal 8 + socket 74
Wire resistance: Max. 1.5 Ohms
- Check wires for shorting to one another.
- Specification: Infinity Ohms

If wiring OK:
- Check Engine Control Module Voltage supply.








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