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 Mass Air Flow (MAF) Sensor J338.

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

Test requirements
- The Motronic Engine Control Module (ECM) J623 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 the Throttle Valve Control Module J338 and is operated by the Motronic Engine Control Module (ECM) J623 according to the specifications of Throttle Position (TP) Sensor G79 / Accelerator Pedal Position Sensor 2 G185.

The Throttle Valve Control Module J338 Contains 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

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) 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):

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

- End diagnosis and switch ignition off.

If the specified values are not obtained:







- Disconnect the Throttle Valve Control Module J338 electrical harness connector - 1 -.

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 specified value was not obtained:
- Replace the Throttle Valve Control Module J338.

If the specified value was obtained:







- Using a Multimeter , check 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 specified value was obtained:
- Replace the Throttle Valve Control Module J338.

If the specified value was not obtained:

Checking wiring

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

If the manufacturers test box is not being used. Perform the following step.
- Remove the Motronic Engine Control Module (ECM) J623.







- Using a Multimeter , check the Throttle Valve Control Module J338 electrical harness connector terminals to the Motronic Engine Control Module (ECM) J623 electrical harness connector T60 terminals for an open circuit.

Throttle Valve Control Motronic Engine Control Module
Module J338 electrical harness (ECM) J623 electrical connector
connector terminals T60 terminals or test box sockets
1 27
2 28
3 15
4 12
5 30
6 29

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) or an open circuit.
- Check the electrical harness connector for damage, corrosion, lose or broken terminals.
- If necessary, repair the faulty wiring connection.

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. Monitors, Trips, Drive Cycles and Readiness Codes

- End of diagnosis.