GM 43 Knock Sensor Error
How to read it
Code 43 reads as 4 flashes, pause, 3 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 43 mean?
Knock Sensor Error
Common causes of 43
- Failed knock sensor
- Broken or shorted knock sensor wire
- Loose sensor or wrong torque changing its signal
- Excessive engine noise from mechanical wear tripping detection
How to fix 43
- Inspect the knock sensor wire for cracks and grounding against the block
- Verify the sensor is torqued to specification
- Tap near the sensor with the engine running and watch for timing retard on a scan tool
- Test sensor and ESC module circuits per the manual
- Repair wiring before replacing the sensor
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 43. Include your vehicle, the issue and a source if you have one.