GM 77 Digital EGR Solenoid 3 Circuit Error
How to read it
Code 77 reads as 7 flashes, pause, 7 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 77 mean?
Digital EGR Solenoid 3 Circuit Error
Common causes of 77
- Failed EGR solenoid winding
- Stuck EGR pintle from carbon
- Chafed wiring near the exhaust
- Faulty ECM EGR driver
How to fix 77
- Read codes with a paperclip jumper
- Test solenoid 3 resistance and compare with the other two
- Inspect wiring routed near hot exhaust parts
- Verify ECM command reaches the valve
- Clean or replace the valve as tests show
- Clear the code and drive to confirm it stays off
Source
Qualified source review
Sources and review
Review: qualified. Read the source limits below.
- GM OBD1 trouble codes, model and year page
live reference page (troublecodes.net)
Supports: code identity and GM meaning
Fetched directly from the linked model page. Single publisher, so the record is qualified, not verified.
https://www.troublecodes.net/GM/92_25R_tbi/
Last updated 2026-09-19.
Report a correction for 77. Include your vehicle, the issue and a source if you have one.