Fuel Trim Long Term Fuel Trim Adaptive Limit Reached Bank 1 (GM)
What does P1168 mean?
The P1168 code means the vehicle's onboard diagnostic system has detected: Fuel Trim Long Term Fuel Trim Adaptive Limit Reached Bank 1 (GM). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Poor fuel economy
- Rough idle or engine surging
- Hesitation during acceleration
- Engine misfires at idle
Probable Causes (Ranked by Likelihood)
- Large vacuum leak in the intake system Very High
- Dirty or failing mass airflow sensor High
- Faulty fuel injectors (clogged or leaking) Moderate
- Low fuel pressure from weak fuel pump Moderate
- Exhaust leak before the upstream O2 sensor Low
Step-by-Step Diagnostic Procedure
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Check long-term fuel trim (LTFT) values on a scan tool -- values beyond plus or minus 25% indicate a problem
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Perform a smoke test to find vacuum leaks
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Clean the MAF sensor with MAF-specific cleaner
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Test fuel pressure at the fuel rail
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Check for exhaust leaks at the manifold
Frequently Asked Questions
What does fuel trim adaptive limit reached mean?
The PCM continuously adjusts fuel delivery based on O2 sensor feedback. P1168 means the PCM has hit its maximum correction limit on Bank 1 and can no longer compensate for the air-fuel imbalance. The root cause must be found and fixed.
What are normal fuel trim values?
Normal long-term fuel trim values should be within plus or minus 10%. Values above 20% indicate a significant lean condition, and values below negative 20% indicate a rich condition. P1168 sets when the limit is exceeded.
Should I fix vacuum leaks before replacing any sensors?
Absolutely. Vacuum leaks are the most common cause of P1168 and are often the cheapest to fix. Always perform a smoke test or careful inspection for vacuum leaks before replacing sensors or fuel system components.