Vehicle Speed Signal, Checking
Vehicle Speed Signal, Checking
Special Tools and Equipment
- VAG1526A
- VAG1527B
- VAG1594A
- VAG1598/31
- VAS5051 with VAG5051/1
or
- VAG1551 with VAG1551/3B
NOTE:
- The vehicle speed signal is generated by the Vehicle Speed Sensor (VSS) -G68- (at transmission) and processed in the instrument cluster.
- The processed signal enters at terminal 54 of the ECM and is used for idle stabilization and tip-in shock reduction during shifting.
Test Requirement:
- Function and display of speedometer OK. Troubleshooting:
Test sequence
- Connect VAS5051 tester or VAG1551 scan tool and select the control module for engine electronics using "address word" 01. Refer to "Scan Tool Testing/Scan Tool Connecting And Initial Checks", Testing and Inspection
Engine must run at idle for this.
WARNING!
Observe safety precautions to reduce the risk of accidents during road test.
When indicated on display:
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select "Read Measuring Value Block" and press -Q- button to confirm input.
When indicated on display:
Read Measuring Value Block Q
Input display group number XXX
- Press buttons -0-, -0- and -5- to select "display group number 005" and press -Q- button to confirm input.
Indicated on display:
Read Measuring Value Block ->
1 2 3 4
- Determining via road test whether vehicle speed is displayed in display field 3.
- If vehicle speed is not display, lift vehicle -if possible using a vehicle lift- until front left wheel is free.
- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. Refer to "Scan Tool Testing/Wire And Component Test Using VAG1598/31 Test Box", Testing and Inspection
- Connect VAG1527B voltage tester to sockets 3 (B+) and 54 (VSS) of VAG1598/31 test box.
- Switch ignition on and turn front left wheel by hand.
- LED must blink (very brief blink signal).
If LED does not blink:
- Check the following wire connection for open circuit and short circuit to Ground (GND) and B+:
Test box VAG1598/31 Socket Instrument cluster Terminal
54
- Repair open circuit or short circuit if necessary.