GM 65 Right Bank O2 Sensor Rich Exhaust Indicated
How to read it
Code 65 reads as 6 flashes, pause, 5 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 65 mean?
Right Bank O2 Sensor Rich Exhaust Indicated
Common causes of 65
- Leaking right bank injector or high fuel pressure
- Saturated charcoal canister or stuck purge
- Faulty fuel pressure regulator
- Contaminated or biased O2 sensor
How to fix 65
- Read codes with a paperclip jumper and check for black exhaust smoke
- Check fuel pressure and leak down
- Inspect the regulator vacuum line for raw fuel
- Check the air filter and purge valve operation
- Test the O2 sensor cross counts on a scan tool
- Repair the fuel fault before replacing the sensor
Source
Qualified source review
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.
https://www.troublecodes.net/gm/
Last updated 2026-09-19.
Report a correction for 65. Include your vehicle, the issue and a source if you have one.