Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsGauges, Warning Devices, and Driver Information Systems Diagnosis and RepairMedium
A customer reports that the odometer on their vehicle has stopped recording mileage, but the speedometer is still functioning correctly. What is the most likely cause?
- AA faulty vehicle speed sensor (VSS).
- BAn internal fault within the instrument cluster.
- CA damaged VSS tone ring.
- DA wiring issue between the VSS and the PCM.
Show answer & explanationAnswer & explanation
Correct answer: B. An internal fault within the instrument cluster.
If the speedometer is working, it indicates that the VSS, VSS tone ring, and the wiring to the PCM, as well as the PCM's ability to calculate speed, are all functional. The odometer's failure while the speedometer works points to an internal issue within the instrument cluster itself, where the odometer function is separately processed or displayed.
Why the other options are wrong
- A. A faulty VSS would affect both the speedometer and odometer, as both rely on its signal.
- C. A damaged VSS tone ring would cause an incorrect or absent VSS signal, affecting both speedometer and odometer.
- D. A wiring issue between the VSS and PCM would typically affect the VSS signal to the PCM, impacting both speedometer and odometer.
Odometer Failure, Speedometer OK
When the speedometer works but the odometer does not, it usually indicates a fault within the instrument cluster itself, specifically with the odometer's internal circuitry or display mechanism.
- Both functions rely on VSS input.
- Speedometer working confirms VSS, wiring, and PCM are functional.
- Odometer failure points to cluster-specific issue.
Memory trick: Odometer's 'STOPPED', speedometer's 'FINE', something's wrong 'INSIDE' the cluster's 'MIND'.