With Manufacturer's Scan Tool
Throttle position sensor, checking
Special tools, equipment, test and inspection devices; required accessories
Special Tools:
^ V.A.G 1526 A hand-held multimeter
^ V.A.G 1551 scan tool or V.A.G 1552 system tester with V.A.G 1551/3 cable
^ VAG 1594 A auxiliary measuring tool set
^ V.A.G 1598/31 test box
^ Wiring diagram
Function
The two throttle position sensors, G79 and G1185, are both on the accelerator and communicate the driver action to the engine control unit independently of each other. The sensors are accommodated in a casing.
Test sequence
- Connect the V.A.G 1551 (V.A.G 1552) scan tool and select the control unit for the engine electronics using "address word" 01. The ignition must be on.
Indicated on display:
- Press the keys "0" and "8" for the function "Read Measuring Value Block" and acknowledge the entry by pressing "Q."
Indicated on display:
- Press the keys "0", "6" and "2" for "display group number 62" and acknowledge the entry by pressing "Q".
Indicated on display (1 - 4 display fields)
- Check the specification of sensor 1 (G79) from the message in field 3, while engine is idling. Specification: 12-97 %
- Check the specification of sensor 2 (G 185) infield 4, while the engine is idling. Specification: 4-49%
Note: The engine control unit converts the voltage of the angle transmitter in percent, based on 5 volts, and displays it (5 volts represents 100 %).
- Slowly actuate the accelerator until full throttle and simultaneously observe the percentages displayed in fields 3 and 4:
^ The percentage in field 3 should increase steadily. Here, the range of tolerances 12-97 % is not totally utilized.
^ The percentage in field 4 should increase steadily. Here, the range of tolerances 4-49 % is not totally utilized.
Note: The value displayed in field 3 should always be about twice as large as the value in field 4.
If the displays do not behave as described:
- Check the power supply and the electrical connections of the throttle position sensors Refer to Powertrain Management.
Checking the power supply and cables to the control unit
- Remove the driver side shelf: Refer to Body and Frame.
- Disconnect the 6 pin connector for the throttle position sensor.
- Turn on the ignition.
- To measure the voltage, connect the multimeter to the following contacts of the connector:
^ Contact 1 + ground
^ Contact 1 + 5
^ Contact 2 + ground
^ Contact 2 + 3
^ Specification: at least 4.5 V
- Turn off the ignition.
If the specifications are not achieved:
- Connect the V.A.G 1598/31 test box to the control unit wiring. Do not connect the engine control unit.
- Use the wiring diagram to check the cables between the test box and the connector for any broken connections.
^ Contact 1 + cavity 72
^ Contact 2+cavity 73
^ Contact 3+cavity 36
^ Contact 4+jack 35
^ Contact 5+jack 33
^ Contact 6+jack 34
^ Line resistance: max. 1.5 0
- Also check the cables for a short circuit to the battery positive terminal or to ground.
- Also check the cables for short circuits between each other.
If no problems can be found in the cables:
- Replace the throttle position sensor (G79).