P1136
Long Term Fuel Trim Additive Fuel — Bank 1 System Too Lean
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P1136 is a BMW-specific code indicating that the long-term fuel trim additive correction for Bank 1 has reached its lean limit. The DME (Digital Motor Electronics) continuously adapts fuel delivery based on oxygen sensor feedback, and this code means the system has been adding extra fuel beyond normal parameters to compensate for a persistent lean condition. The adaptation has exceeded the allowable correction range.
This code is functionally similar to BMW's P1083 and the generic P0171, but specifically refers to the long-term adaptive correction rather than the instantaneous fuel control. It's commonly seen on BMW M52, M54, and N52 engines and typically appears alongside P1083 or P0171 codes. The root causes are identical to other lean codes — vacuum leaks being the most prevalent.
Diagnosis should follow a systematic approach starting with the most common failure points on BMW engines. Inspect the CCV (crankcase ventilation) valve and hoses, the intake boot between the MAF and throttle body, and all vacuum lines under the intake manifold. A smoke test is strongly recommended as it reveals even small leaks that are nearly impossible to find by visual inspection alone. If no vacuum leaks are found, test the MAF sensor output against known-good values at various RPMs, and check fuel pressure at the rail with a mechanical gauge. On BMW engines with over 100,000 miles, consider replacing the upstream O2 sensor as sensor degradation can contribute to inaccurate fuel trim adaptation.
Severity
Symptoms
- •Check Engine Light on
- •Unstable or rough idle
- •Poor throttle response and hesitation
- •Decreased fuel economy
- •Engine may stumble during cold starts
- •Occasional lean misfire at idle
Likely Causes
Cracked intake boots, deteriorated vacuum hoses, or leaking CCV (crankcase ventilation) valve introduce unmetered air that causes persistent lean fuel trim corrections.
A slow-responding or biased upstream O2 sensor on Bank 1 reports inaccurate lean readings, causing the DME to add compensating fuel until the long-term trim limit is exceeded.
A contaminated MAF sensor underestimates airflow, leading to insufficient fuel delivery and long-term lean adaptation on Bank 1.
Low fuel pressure from a weak pump, clogged filter, or restricted injectors prevents adequate fuel delivery to match actual airflow.
An exhaust manifold crack or header gasket leak draws in ambient air past the pre-cat O2 sensor, causing false lean readings.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Perform smoke test and repair all vacuum leaks
- Replace upstream oxygen sensor on Bank 1
- Clean or replace MAF sensor
- Check fuel pressure and replace pump or filter if needed
- Inspect and repair exhaust manifold leaks