Accelerator Position Sensors, Testing

Accelerator Position Sensors, Testing







Special tools and equipment
- VAG 1526 A
- VAG1594 A
- VAG 1598/31
- VAS 5051 with VAS 5051/1

Accelerator position sensors -G79- and -G185- are located on the accelerator pedal. Both senders inform the engine control module of the driver's throttle requirement (pedal position), but each functions completely independently of the other (redundancy principle). Both sensors are located in a single housing.

Test sequence
- Connect the vehicle diagnostic, testing and information system VAS 5051, Vehicle Diagnostic, Testing and Information System VAS 5051, Connecting and Selecting Functions , and select the vehicle system "01 - Engine electronics" from the menu. When doing this the ignition should be switched on.







Display on VAS 5051:
- Select the diagnosis function "08 - Read data block" from the menu -1-.







Display on VAS 5051:
1 - Enter display group
(figures up to 255)
- Using the keypad -2-, enter "062" to select Display group 062 and confirm entry with Q button.







Display on VAS 5051:
- Check display values for electronic throttle potentiometer voltages in display zones -3- and -4-.







NOTE: The engine control module converts the voltage readings from the angle sensors into percentages of 5 V and displays them as percentages. (A supply voltage of 5 V is equivalent to 100%.)

- Observe display zones 3 and 4.
- Slowly depress accelerator to full throttle position.

The percentage value in display zone 3 should rise steadily between 12 and 97 % but without covering the full range of values.

The percentage value in display zone 4 should also rise steadily but without covering the full range of values (in this case 4 to 49 %).

NOTE: The value shown in display zone 3 should always be about twice as high as the value shown in display zone 4.

- Press the <- button to exit from the function "08 - Read data block".

If the display values do not appear as described:
- Test voltage supply and wiring to accelerator position senders

Testing voltage supply to accelerator position senders
- Remove storage compartment on driver's side.
- Unplug connector for accelerator position sender.
- Switch ignition on.







- Connect multimeter (voltage measurement range) as follows:

Connector Contact Specification
1 + Ground approx. 5 V
1 + 5 approx. 5 V
2 + Ground approx. 5 V
2 + 3 approx. 5 V

If the specifications are obtained:
- Test the signal wires.

If the specifications are not obtained:
- Test wiring between engine control module and accelerator position sensors.

Testing wiring
- Connect test box VAG 1598/31 to wiring harness for engine control module. Do not connect to the engine control module itself.







- Test for open circuit and short to positive or Ground in the following wiring connections:

Connector Contact Test box VAG 1598/31 Socket
1 72
2 73
3 36
4 35
5 33
6 34

- Correct any open/short circuit as necessary.

If no malfunction is detected in wiring:
- Replace accelerator position sensors.