GM 45 Oxygen Sensor Error Rich Condition Indicated
How to read it
Code 45 reads as 4 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 45 mean?
Oxygen Sensor Error Rich Condition Indicated
Common causes of 45
- Leaking fuel injector or high fuel pressure
- Saturated charcoal canister purging excess vapor
- Restricted air filter or intake
- Failed oxygen sensor stuck rich
How to fix 45
- Check fuel pressure and leak down against specification
- Inspect the air filter and intake duct for restriction
- Watch block learn and integrator values on a scan tool
- Test injectors for leakage before replacing the sensor
- Replace the sensor only if mixture stays rich with fuel control normal
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 45. Include your vehicle, the issue and a source if you have one.