Cylinder 1 Fuel Trim at Min Limit
The P029B code indicates that the engine control module (ECM) has detected the fuel trim for cylinder 1 is at its minimum limit, meaning the system is trying to reduce fuel delivery as much as possible due to a rich condition. This can be caused by excessive fuel pressure, a leaking fuel injector, or a faulty oxygen sensor, leading to an overly rich air-fuel mixture in cylinder 1.
01. Most Common Causes
- Faulty or leaking fuel injector on cylinder 1
- High fuel pressure (e.g., faulty fuel pressure regulator)
- Oxygen sensor (O2) or air-fuel ratio sensor malfunction
- Engine mechanical issue (e.g., low compression on cylinder 1)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Rough idle or misfire on cylinder 1
- Poor fuel economy
- Excessive fuel smell from exhaust
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect fuel injector on cylinder 1 for leakage or electrical issues.
Step 3: Check fuel pressure with a gauge to ensure it's within spec.
Step 4: Test oxygen sensor readings and compare bank 1 sensor 1 to bank 2 if applicable.
Step 5: Perform a compression test on cylinder 1 to rule out mechanical problems.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as a rich condition can damage the catalytic converter and other components. Short trips to a repair shop are acceptable.
How much does it cost to fix?▼
The cost varies depending on the cause. A faulty oxygen sensor may cost $50-$150, while a fuel injector replacement can be $200-$400. Diagnosis fees are typically $100-$150.