GM 64 Right Bank O2 Sensor Lean Exhaust Indicated
How to read it
Code 64 reads as 6 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 64 mean?
Right Bank O2 Sensor Lean Exhaust Indicated
Common causes of 64
- Vacuum leak on the right bank
- Low fuel pressure or weak injector
- Exhaust leak pulling air into the pipe
- Aging O2 sensor reading slow
How to fix 64
- Read codes with a paperclip jumper and check fuel trim if a tool shows it
- Spray test for vacuum leaks around the intake and hoses
- Check fuel pressure against spec
- Inspect the exhaust manifold for cracks or leaks
- Replace the O2 sensor if it stays lean with no leaks
- Clear the code and road test
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 64. Include your vehicle, the issue and a source if you have one.