Throttle Position Sensor: Testing and Inspection
Throttle Position (TP) Sensor -G79 And Sender -2- Accelerator Pedal Position -G185, Checking
Component location of Throttle Position (TP) sensor -G79 and Sender -2- accelerator pedal position
The Throttle Position (TP) Sensor -G79 and Sender -2- for accelerator pedal position -G185 are located at the accelerator pedal. Both sensors inform (completely independently of the other) the engine control module of the driver's throttle requirement (pedal position). Both sensors are located in a single housing.
- Connect vehicle diagnostic, testing and information system VAS5051 or VAG1551 scan tool and select engine electronics control module by entering address word "01 ". When doing this the ignition must be switched on. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAS 5051/ VAG 1551 Scan Tool" Testing and Inspection
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select function "Read Measuring Value Block" and confirm entry with -Q- button.
Indicated on display
Read Measuring Value Block Q
Input display group number XXX
- Press buttons -0-, -6- and -2- to select "display group number 062" and confirm entry with -Q- button.
Indicated on display
Read Measuring Value Block 62 ->
1 2 3 4
- Observe specification for electronic throttle potentiometer voltages.
Display Group 062:
- Observe display fields 3 and 4
- Slowly depress accelerator pedal to full throttle position.
The percentage value in display field 3 should rise steadily, but without covering the full tolerance range between 3 - 93 %.
The percentage value in display field 4 should also rise steadily but without covering full range of values (in this case 4 - 49 %).
NOTE: The value shown in display field 3 should always be about the double of the value shown in display field 4.
If the display values do not appear as described:
- Check voltage supply and wiring to accelerator position sensors
Checking voltage supply of accelerator position sensors
- Remove storage compartment on driver's side.
- Disconnect harness connector for accelerator position sensor.
- Switch ignition on.
- Connect hand-held multimeter (voltage range) between the following sockets on the connector:
6-pin connector on Specification
wiring harness, socket
2 + Ground (GND) approx. 5 V
1 + 3 approx. 5V
5 + Ground (GND) approx. 5 V
5 + 4 approx. 5V
If the specifications are obtained:
- Check signal wiring.
If the specifications are not obtained:
- Check wiring between Engine Control Module (ECM) and accelerator position sensors.
Checking wiring
- Connect VAG1598/31 test box to wiring harness for engine control module. Do not connect to the engine control module itself. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG1598/31 Test Box" Testing and Inspection
- Check for open circuit and short to B+ or Ground (GND) in the following wiring connections:
Connector VAG1598/31 test box
socket socket
1 72
2 73
3 36
4 35
5 33
6 34
- Repair any open/short circuit as necessary.
If no wiring malfunction is detected:
- Replace accelerator position sensors.
NOTE: After replacing accelerator position sensor, on vehicles with automatic transmission carry out adaptation of Kick-Down switch.