With Generic Scan Tool

Throttle Valve Control Module J338 , checking

Note:
- Use only gold-plated terminals when servicing terminals in harness connector of Mass Air Flow (MAF) Sensor 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�C.

Function

Throttle valve operation occurs by an electric motor ( Throttle Drive (for Electronic Power Control (EPC)) G186 ) in the Throttle Valve Control Module J338 . It is operated by the Motronic Engine Control Module (ECM) J220 and the Throttle Position (TP) Sensor G79 / Accelerator Pedal Position Sensor 2 G185.

The Throttle Valve Control Module J338 is made up of the following components:
- 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

The Throttle Valve Control Module J338 cannot be serviced separately and must be serviced as a unit.

Test procedure
- Perform a preliminary check to verify the customers complaint. Service and Repair

Start diagnosis

Function test

- Connect the scan tool.

- Switch ignition on.

- Using the scan tool, check the throttle valve position (absolute) at idle stop:






- 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:






- End diagnosis and switch ignition off.

If the specified values are not obtained:

- Remove the Throttle Valve Control Module J338 far enough so that the electrical connector terminals are reached.






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

Checking 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�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.

- Throttle Position (TP) Sensor G79 / Accelerator Pedal Position Sensor 2 G185, checking. Throttle Position (TP) Sensor, Checking

Checking voltage supply and wiring

- Switch 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 not obtained:

Checking wiring

If the manufacturers test box is being used. Perform the following step.

- Install the test box Test Box 105 Pin VAG1598/31.

If the manufacturers test box is not being used. Perform the following step.

- Remove the Motronic Engine Control Module (ECM) J220. Service and Repair






- 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 T121 terminals for an open circuit according to the wiring diagram.






Specified value: 1.5 Ohms max.

If the specification was 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, lose or broken terminals.

- Erase the DTC memory. Diagnostic Mode 4: Reset/Erase Diagnostic Data

- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:

- Replace the MFI Engine Control Module (ECM) J220. Service and Repair

- Assembly is performed in the reverse of the removal.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory.
2. If necessary, erase the DTC memory.
3. If the DTC memory was erased, generate readiness code.

End diagnosis