DTC 24
UPDATED BY TSB # 9204011, DATED OCTOBER 1992Code 24 Circuit Diagram:
A�Code 24 Vehicle Speed Sensor Diagnostic Chart:
CIRCUIT DESCRIPTION
The ECM applies and monitors 12 volts on CKT A10. CKT A10 connects to the vehicle speed buffer which alternately grounds CKT 437 when drive wheels are turning. This pulsing action takes place about 2000 times per mile and the ECM will calculate vehicle speed based on the time between "pulses".
"Scan" reading should closely match with speedometer reading with drive wheels turning. To prevent misdiagnosis, the technician should identify the type of Vehicle Speed Sensor (VSS) used prior to using this chart. Disregard a Code 24 set when drive wheels are not turning.
TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.
1. Code 24 will set if vehicle speed is less than 2 mph when:
- Engine speed is greater than 1400 rpm
- TPS is less than 5% (closed throttle)
- Low load condition (less than 25 kPa of vacuum)
- All conditions met and accumulated for 5 seconds.
Disregard Code 24 that sets when drive wheels are not turning.
DIAGNOSTIC AIDS
"Scan" should indicate a vehicle speed whenever the drive wheels are turning.
See DIAGNOSIS BY SYMPTOM - NO TROUBLE CODES STORED.