Throttle Valve Control Module, Checking

Special Tools And Workshop Equipment Required 

• Multimeter
• Wiring diagram.

Test Requirements 

• The Motronic Engine Control Module (ECM) - J623- fuses OK.
  Fig 1: Fuses On E-Box In Engine Compartment, Left Side

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• 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) -J623- 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. Refer to PRELIMINARY CHECK 

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%

-- 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 Ω (At 20° C) 

If the specified value was Not obtained:

-- Replace the Throttle Valve Control Module - J338-. Refer to the Repair Information.

If the specified value was obtained:

-- Check the voltage supply of the Throttle Valve Control Module -J338- from the Motronic Engine Control Module (ECM) -J623- as instructed below.

Checking voltage supply and wiring

-- Switch the ignition on.

-- Using a multimeter, check the Throttle Valve Control Module -J338- electrical harness connector, terminals 2 to 6 for voltage from the ECM.

Specified Value: At Least 4.5 V 

-- Switch the ignition off.

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-. Refer to the Repair Information.

-- 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 according to the wiring diagram.

Throttle Valve Control Module -J338- electrical harness connector terminals	Motronic Engine Control Module (ECM) -J623- electrical connector T60 terminals or test box socket
1	54
2	12
3	46
4	41
5	47
6	43

Specified Value: 1.5 Ω Max. 

If the specified value was Not obtained:

-- Check the wiring for an open, high resistance or short to ground.

-- If necessary, repair the faulty wiring connection.

-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

If no fault is detected in the wiring and the voltage supply was Not OK:

-- Replace the Motronic Engine Control Module (ECM) -J623-. Refer to the Repair Information.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .