Throttle Position Sensor: Testing and Inspection
The Throttle Position sensor G79 is located on the accelerator pedal and transfers Throttle Position information to the Engine Control Module.Special Tools, Testers And Auxiliary Items:
- VAG 1551/1552 Scan Tool with VAG 1551/3 adaptor cable
- VAG 1598/22 Test Box
- VW 1594 adaptor kit
- VAG 1527B LED tester
- Wiring diagram
Test Sequence:
- Connect VAG 1551/1552 Scan Tool
- Switch ON ignition
- Press 0 and 1 buttons to select address word 01 "engine electronics"
Display will appear as shown:
Rapid data transfer HELP
Select function XX
- Press 0 and 8 buttons to select Function 08 "Read measuring value block"
- Press Q button to enter input
Display will appear as shown:
Read measuring value block HELP
input display group number XX
- Press 0 and 2 buttons to select "display group 2"
- Press Q button to enter input
- Observe value in display field 2 (accelerator pedal position)
Display will appear as shown:
Read measuring value block 2 ->
rpm 0.0% 0 1 0 18.4°C
Specification: 0.0 % (accelerator pedal not operated)
- Observe value in display field 3
Display will appear as shown:
Read measuring value block 2 ->
rpm 0.0% 0 1 0 18.4°C
Specification:
0 1 0 (accelerator pedal not operated)
0 0 0 (accelerator pedal operated)
- Press accelerator pedal down slowly, display field 2 must increase steadily to 100 % (accelerator pedal fully depressed)
Display will appear as shown:
Read measuring value block 2 ->
rpm 100.0% 0 1 0 18.4°C
NOTE for vehicles with automatic transmission ONLY: The kickdown switch pressure point must be distinctly felt BEFORE the Wide Open Throttle stop position is reached.
If specified end value not reached:
- Adjust Throttle Position sensor
If display value does not change or is irregular:
- Check Throttle Position sensor G79 as follows:
- Switch OFF ignition
- Disconnect Throttle Position sensor harness connector
- Switch Fluke 83 multimeter to resistance range
- Measure resistance between sensor terminals 1 and 3 using jumper wires from VW 1594 adaptor kit:
Accelerator not depressed: Closed Throttle position
Specification: 1000 to 1500 Ohms.
Accelerator depressed: Wide Open Throttle position
Specification: 1500 to 2500 Ohms.
If specifications not obtained:
- Replace Throttle Position sensor G79
- Display the readiness code
If DTC memory was erased:
- Create readiness code again
If specifications obtained:
- Switch OFF ignition
- Disconnect Throttle Position sensor harness connector
- Connect VAG 1598/18 Test Box to ECM harness connector
- Check following wiring connections for: Open circuits and/or Short to positive or negative:
Wiring from connector terminal 1 to Test Box socket 15
Wiring from connector terminal 2 to Test Box socket 57
Wiring from connector terminal 3 to Test Box socket 55
Wiring from connector terminal 4 to Test Box socket 65
Wiring from connector terminal 5 to Test Box socket 62
Wiring from connector terminal 6 to Test Box socket 33
- Repair any open/short circuit as necessary
If neither an open or short circuit exists:
- Replace Diesel direct injection system ECM
- Display the readiness code
If DTC memory was erased:
- Create readiness code again