S4 V8-42L (BHF) (2004) - Vehicle Speed Sensor Testing
Vehicle Speed Sensor: Testing and Inspection
Speed Signal, Checking
Test requirement:
-
Function and display of speedometer OK. Troubleshooting.
WARNING: To reduce the risk of accident during road tests, always observe safety precautions.
-
Connect diagnostic tester. See: Computers and Control Systems/Testing and Inspection/Reading and Clearing Diagnostic Trouble Codes/Scan
Tool Connecting/Diagnostic Tester, Connecting
-
Start engine and let run at idle.
-
In diagnostic function "33 - OBD", select "Diagnostic mode 1 - Check measuring values".
-
Select the desired measuring value "PID 13: Vehicle speed".
-
Perform a road test, and have the 2nd person observe the indication on the display.
-
End diagnosis and switch ignition off.
If no speed is displayed:
The speed signal is transferred from the Engine Control Module (ECM) to the instrument cluster via wire connection or via CAN-Bus, depending on
version.
-
Checking wire connections
-
Check terminal resistance for CAN-Bus
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check DTC memory see "Mode 3: Check DTC memory". See: Computers and Control Systems/Testing and Inspection/Scan Tool Testing and
Procedures/Mode 3: Check DTC Memory
2. If necessary, erase DTC memory see "Mode 4: Reset/erase diagnostic data". See: Computers and Control Systems/Testing and Inspection/Scan
Tool Testing and Procedures/Mode 4: Reset/Erase Diagnostic Data
3. Generate readiness code. See: Computers and Control Systems/Testing and Inspection/Monitors, Trips, Drive Cycles and Readiness
Codes/Readiness Code, Generating