GM 24 Vehicle Speed Sensor Error
How to read it
Code 24 reads as 2 flashes, pause, 4 flashes on the check-engine light. Jump terminals A and B on the ALDL connector with the key off, then turn the key on with the engine off and count the check-engine flashes.
New to flash codes? The How to Read GM OBD-I Codes with a Paperclip walks through the test and what the numbers mean. The general OBD-I guide covers the rest.
What does GM code 24 mean?
Vehicle Speed Sensor Error
Common causes of 24
- Failed vehicle speed sensor in the transmission
- Damaged speedometer cable or drive gear on cable models
- Open or shorted VSS wiring to the ECM
- Faulty instrument cluster buffer box on some trucks
How to fix 24
- Confirm the speedometer works since it shares the VSS signal on many models
- Retrieve codes with a paperclip across ALDL pins A and B after a short drive
- Inspect sensor wiring at the transmission for damage
- Test sensor output pulse while the drive wheels turn
- Replace the sensor only after wiring and drive gear check good
Sources and review
Review: qualified. Read the source limits below.
- GM and Chevrolet OBD1 Trouble Codes (ALDL Fault Code List)
live reference page (troublecodes.net)
Supports: code identity and GM meaning
Fetched directly. Single publisher, so the record is qualified, not verified. Causes and check order are curator-written from the circuit the code names.
Last updated 2026-09-19.
Report a correction for 24. Include your vehicle, the issue and a source if you have one.