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Electronic Throttle Control Module: Testing and Inspection



Throttle Valve Control Module, Checking

NOTE: Use only gold-plated terminals when servicing terminals in harness connector of Throttle Valve Control Module J338.

Special tools, testers and auxiliary items required
- Multimeter.
- Wiring diagram.

Test requirements
- The Motronic Engine Control Module (ECM) J220 fuses OK.
- Battery voltage at least 12.5 volts.
- All electrical consumers such as, lights and rear window defroster, switched off.
- Vehicles with automatic transmission, shift selector lever into position "P" or "N".
- A/C switched off.
- Ground (GND) connections between engine/transmission/chassis OK.
- Throttle valve must not be damaged or dirty.
- Coolant Temperature at least 80 degrees C.

Function
Throttle valve operation occurs by an electric motor ( Throttle Drive (for Electronic Power Control (EPC)) G186 ) in Throttle Valve Control Module J338. It is operated by Motronic Engine Control Module (ECM) J220 according to specifications of Throttle Drive Angle Sensor 1 (for Electronic Power Control (EPC)) G187 / Throttle Drive Angle Sensor 2 (for Electronic Power Control (EPC)) G188.

Components of Throttle Valve Control Module J338 :
- Throttle Drive (for Electronic Power Control (EPC)) G186
- Throttle Drive Angle Sensor 1 (for Electronic Power Control (EPC)) G187
- Throttle Drive Angle Sensor 2 (for Electronic Power Control (EPC)) G188

Test procedure
- Perform a preliminary check to verify the customers complaint. General Diagnosis

Start diagnosis
- Connect the scan tool.
- Switch ignition on.
- Using the scan tool, check the throttle valve position (absolute) at idle stop:

Diagnostic text Specified value
Throttle valve position (absolute)
Idle stop 3.0 to 25.0%

- Slowly depress the accelerator pedal to Wide Open Throttle (WOT) stop while observing the percentage display. The percentage display must increase uniformly.
- Using the scan tool, check the throttle valve position (absolute) at Wide Open Throttle (WOT) stop:

Diagnostic text Specified value
Throttle valve position (absolute)
Wide Open Throttle (WOT) stop 84.0 to 97.0%

- End diagnosis an switch ignition off.

If the specified values are not obtained:







- Remove the air hose - arrows -.







- Disconnect the Throttle Valve Control Module J338 electrical harness connector - 3 -.

Checking internal resistance
- Using a multimeter, check the Throttle Drive (for Electronic Power Control (EPC)) G186 at the Throttle Valve Control Module J338 terminals 3 to 5 for resistance.

Specified value: 1.0 to 5.0 Ohms (at 20 degrees C)

If the specification was not obtained:
- Replace the Throttle Valve Control Module J338.

If the specification was obtained:
- Check the voltage supply of the Throttle Valve Control Module J338 to the Motronic Engine Control Module (ECM) J220.

Checking voltage supply and wiring
- Switch the ignition on.







- Using a Multimeter, check the Throttle Drive (for Electronic Power Control (EPC)) G186 at the Throttle Valve Control Module J338 electrical harness connector terminals 2 to 6 for voltage.

Specified value: at least 4.5 V
- Switch the ignition off.

If the specification was obtained:
- Replace the Throttle Valve Control Module J338.

If the specification was not obtained:

Checking wiring
If the manufacturers test box is being used. Perform the following step.
- Install the test box VAG1598/31.

If the manufacturers test box is not being used. Perform the following step.
- Remove the Motronic Engine Control Module (ECM) J220.







- Using a Multimeter, check the Throttle Drive (for Electronic Power Control (EPC)) G186 at Throttle Valve Control Module J338 electrical harness connector terminals to the Motronic Engine Control Module (ECM) J220 electrical harness connector terminals for resistance.

Throttle Valve Control Module Motronic Engine Control Module (ECM)
J338 electrical harness J220 electrical harness connector
connector terminals terminals or test box sockets
1 92
2 83
3 117
4 84
5 118
6 91

Specified value: 1.5 Ohms max.

If the specification is not obtained:
- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).
- If necessary, repair the faulty wiring connection.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

If no malfunction is detected in the wiring and if the voltage supply was not OK:
- Erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory
- Perform a road test to verify repair.

If the DTC does not return:
Repair complete, Generate readiness code. Readiness Code
- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:
- Replace the Motronic Engine Control Module (ECM) J220.
- Assembly is performed in the reverse of the removal.

Final procedures
After repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If the DTC memory was erased, generate readiness code.

End of diagnosis
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