Chrysler 51 Fuel System Lean
How to read it
Code 51 reads as 5 flashes, pause, 1 flash on the check-engine light. Cycle the ignition key on, off, on, off, then leave it on with the engine off, and count the flashes on the power loss or check-engine light.
New to flash codes? The How to Read Chrysler OBD-I Codes with the Key Cycle walks through the test and what the numbers mean. The general OBD-I guide covers the rest.
What does Chrysler code 51 mean?
Fuel System Lean
Common causes of 51
- Vacuum leak leaning the mixture
- Low fuel pressure from a weak pump or clogged filter
- Dirty fuel injectors with poor spray
- Exhaust leak ahead of the oxygen sensor skewing the reading
How to fix 51
- Check fuel pressure against specification under load
- Inspect vacuum hoses and intake gaskets for leaks
- Watch oxygen sensor cross counts on a scan tool
- Repair leaks and fuel delivery faults before replacing the sensor
- Replace the sensor only if the mixture stays lean with fuel control normal
- Clear the code and road test
Sources and review
Review: qualified. Read the source limits below.
- Chrysler OBD-I trouble codes, model and year page
live reference page (troublecodes.net)
Supports: code identity and Chrysler meaning
Fetched directly from the linked model page. Single publisher, so the record is qualified, not verified. Causes and check order are curator-written from the circuit the code names.
- Chrysler OBD-I trouble codes, model and year page
live reference page (troublecodes.net)
Supports: code identity and Chrysler meaning
Fetched directly from the linked model page. Single publisher, so the record is qualified, not verified. Causes and check order are curator-written from the circuit the code names.
Last updated 2026-10-10.
Report a correction for 51. Include your vehicle, the issue and a source if you have one.