Electronic Throttle Control Module: Testing and Inspection

Throttle Valve Control Module J338, 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) J623 Fuse S243 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 via 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) J623 according to specifications of Throttle Position (TP) Sensor G79 / Accelerator Pedal Position Sensor 2 G185.

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

Function test
- 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 and switch ignition off.

If the specified values are not obtained:







- Remove the rear engine cover - arrows -.
- 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 - 6 -.

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 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) J623.

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 not obtained:







- 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) J623 electrical harness connector T121 terminals for an open circuit.

Throttle Valve Control Module Motronic Engine Control Module
J338 electrical harness (ECM) J623 electrical connector
connector terminals T121 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, lose or broken terminals.

If no malfunction is detected in the wiring and if the voltage supply was not OK:
- Replace Motronic Engine Control Module (ECM) J623.

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.