Powertrain Controls - ECM/PCM

DTC 24:

Vehicle Speed Sensor Circuit:

Circuit Description:
A vehicle speed signal is provided to the PCM by the Vehicle Speed Sensor (VSS). This sensor produces a pulsing waveform voltage whenever vehicle speed is greater than 2 mph. The voltage level or amplitude and the frequency of pulses increases with vehicle speed. The PCM conditions this signal and calculates the vehicle speed. The PCM will then supply the signal to the instrument panel (4000 pulses per mile).

DTC 24 Will Set When:
DTC 28 is not present, brake is released, engine RPM is greater than 3000, vehicle speed is less than 5 mph with all conditions met for 4 seconds.

Action Taken (PCM will default to):
The vehicle cruise control will be disabled and the MIL will become illuminated.

DTC 24 Will Clear When:
A current DTC 24 will clear after each ignition key cycle. A History DTC 24 will clear after 50 consecutive ignition key cycles without a current DTC 24 being stored.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. Disregard DTC 24 that sets when drive wheels are not turning. The sensor only produces a signal if drive wheels are turning faster than 3 mph.

Diagnostic Aids:
Tech I scan tool should indicate a vehicle speed whenever the drive wheels are turning greater than 3 mph.

A problem in CKT 389 will not affect the VSS input or the readings on a Tech 1 scan tool.

Check CKT 1232 and CKT 1233 for proper connections to be sure they are clean and tight, and that the harness is routed correctly. Refer to "intermittents" in "Diagnosis By Symptom." Testing and Inspection

(A/T) equipped vehicles - A faulty or misadjusted Park/Neutral Position (PNP) switch can result in a false DTC 24. Use a Tech 1 scan tool and check for proper signal while in drive. Refer to CHART C-1A for PNP switch diagnosis check. Chart C-1A Park/Neutral Switch Diagnosis