Diagnostic trouble code P1139 is a manufacturer-specific powertrain fault code. Because it is manufacturer-specific, its exact definition depends entirely on the vehicle make, model, and application.
Exact vehicle application must be verified before diagnosis. The code identifies a detected condition in a specific subsystem, but further testing is required to identify the root cause.
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Key Takeaways
- P1139 is a manufacturer-specific code, meaning its definition varies between automakers like Volkswagen and Audi.
- On VW and Audi applications, it indicates a long-term fuel trim additive bank 2 system too rich condition.
- Possible causes include failing fuel injectors, excessive fuel pressure, or a stuck open EVAP purge valve.
- Diagnosis requires verifying the exact factory definition and testing the relevant fuel system components.
P1139 Code Description and Implications
Because P1139 is manufacturer-specific, there is no single universal definition. This trouble code identifies a detected condition, but the exact monitored system depends on the vehicle make and model.
Some Volkswagen and Audi applications: P1139 indicates a “Long Term Fuel Trim Additive Bank 2 System Too Rich” fault. The engine control module detects that the idle fuel adaptation for bank 2 has reached its maximum rich limit.
Some other applications: P1139 may indicate an oxygen sensor circuit fault or a secondary air injection system issue, depending on the specific manufacturer calibration.
Common Causes of the P1139 Code
The underlying cause depends entirely on the verified factory definition for the specific vehicle application.
For VW and Audi applications, possible causes include a leaking fuel injector on bank 2, excessive fuel pressure from a failing regulator, a stuck open EVAP purge valve, or a contaminated mass airflow sensor.
For applications monitoring other systems, causes may involve a failing oxygen sensor, damaged sensor wiring, poor electrical connections, or a secondary air injection system leak.
Symptoms Associated With P1139
Symptoms vary depending on the underlying system fault and the vehicle manufacturer.
On VW and Audi applications with a fuel trim fault, symptoms can include rough idling, decreased fuel efficiency, a rich exhaust smell, and an illuminated Check Engine Light.
On applications with an oxygen sensor or secondary air fault, symptoms may include poor engine performance, failed emissions tests, and an illuminated Check Engine Light.
Diagnosing the P1139 Trouble Code
Diagnosis must begin by confirming the exact factory definition for the specific make, model, and year.
For VW and Audi applications, technicians inspect the EVAP purge valve for sticking, test the mass airflow sensor readings, and check for leaking fuel injectors or high fuel pressure on bank 2.
For applications monitoring the oxygen sensor or secondary air system, technicians inspect the relevant circuits, test the component operation, and verify the system using live data.
Repairing the P1139 Issue
Repairs must follow confirmed diagnosis based on the specific vehicle application.
If a fuel trim fault is confirmed on a VW or Audi application, the confirmed failed component such as the EVAP purge valve, fuel injector, or fuel pressure regulator must be replaced or repaired.
If an oxygen sensor or secondary air fault is confirmed, the relevant sensor, valve, or damaged wiring harness must be replaced or repaired.
Cost Considerations for P1139 Repairs
Cost depends on diagnostic time, component accessibility, required parts, programming requirements, and labor.
Replacing an EVAP purge valve or cleaning a mass airflow sensor involves minimal parts cost and standard labor times.
Conversely, replacing fuel injectors or an electronic oxygen sensor requires specific component replacement and potential adaptation procedures using a scan tool.
Prevention Strategies for Future Occurrences
Some electrical and mechanical failures cannot be reliably prevented.
Using high-quality fuel and replacing fuel filters at recommended intervals can help protect fuel injectors and maintain proper fuel system operation.
Inspecting exposed engine wiring harnesses and vacuum hoses for damage can help prevent electrical faults and false air or vapor intrusion.
Troubleshooting Tips and Best Practices
Never assume P1139 is a universal fuel trim code. Always verify the exact definition for the specific vehicle before purchasing parts.
Do not ignore related codes. A fuel trim fault may appear alongside other mixture codes, while an oxygen sensor fault may appear alongside catalyst efficiency codes.
Check for technical service bulletins applicable to your exact vehicle application, as manufacturers frequently release updated components or revised software calibrations for recurring faults.
More OBD-II Codes
| P1138 | P1140 | P0172 | P1146 |
| P1137 | P1141 | P0171 | P1147 |
| P1136 | P1142 | P0174 | P1148 |
| P1135 | P1143 | P0170 | P1149 |
| P1134 | P1144 | P0173 | P1150 |
| P1133 | P1145 | P1151 | P1132 |
Frequently Asked Questions
Is P1139 a generic or manufacturer-specific code?
No. P1139 is a manufacturer-specific code. Its exact definition varies significantly between automakers, so the factory service information for the specific vehicle must be consulted.
Can I drive my car with a P1139 code?
It depends on the application. If P1139 indicates a rich fuel condition, fuel efficiency will drop. If it is an oxygen sensor fault, emissions may increase.
Will disconnecting the battery clear the P1139 code?
Disconnecting the battery may temporarily clear the code, but it does not repair the underlying electrical or mechanical fault. It also resets readiness monitors and fuel trims.
Can a vacuum leak cause a P1139 code?
A vacuum leak normally causes a lean condition. However, a stuck open EVAP purge valve acts like a vacuum leak pulling fuel vapors, causing a rich condition.
Does P1139 always mean the oxygen sensor is bad?
No. While a failing oxygen sensor is a cause on specific applications, the code can also indicate a fuel trim fault caused by a failing MAF sensor or leaking injector.
What Should You Do About the P1139 Code?
Confirm the exact factory definition and diagnostic procedure for your specific vehicle application. Because P1139 is manufacturer-specific, identifying whether it relates to a fuel trim additive fault or an oxygen sensor circuit is mandatory.
Follow the applicable manufacturer diagnostic steps to test the relevant system and components. Once the root cause is confirmed, complete the necessary repairs and verify that the system operates correctly and the code does not return.
