24-168
Vehicle speed signal, checking
Notes:
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:
Electrical Wiring Diagrams, Troubleshooting &
Component Locations binder
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24-178
Brake light switch and brake pedal
switch, checking
Note:
For safety reasons, the instruction from the
accelerator pedal sensor (potentiometer) to the
ECM to open the throttle valve is suppressed
when brake is being operated. This requires the
brake light switch signal and also the brake pedal
switch signal in the control module.
If brake pedal is operated with accelerator pedal
constantly depressed, engine is immediately
regulated down to idle speed. A faulty switch can
lead to undesired regulation.
Test sequence
- Connect VAS5051 tester or VAG1551 scan tool
and select the control module for engine
electronics using "address word" 01 Page 01
-
9 .
Ignition must remain switched on for this.Rapid data transfer
HELP
Select function XX
When indicated on display:
- Press buttons -0- and -8- to select "Read Measuring Value Block" and
press -Q- button to confirm input.
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