Throttle Valve Control Module, Checking: Notes

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 UNITED STATES, 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.

Test procedure 

-- Observe safety precautions. Refer to SAFETY PRECAUTIONS 

-- Observe Clean Working Conditions. Refer to CLEAN WORKING CONDITIONS 

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .

Start diagnosis 

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) -J623- according to specifications of Throttle Position (TP) Sensor -G79-/Kickdown Switch/Closed Throttle Switch -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%

-- 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 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-.

--.