Subaru OBD-II 1996 & Newer models DTC P1139 – Front oxygen (A/F) sensor #1 heater circuit performance/range problem
DTC P1139 meaning on Subaru OBD-II 1996 & Newer models
DTC P1139 indicates a Front oxygen (A/F) sensor #1 heater circuit performance/range problem on Subaru vehicles equipped with OBD-II systems from 1996 onwards.
Subaru OBD-II 1996 & Newer models DTC P1139 symptoms
- Check Engine Light (CEL) illuminated on the dashboard
- Poor fuel economy
- Engine may run rough or hesitate
- Reduced engine performance
Subaru OBD-II 1996 & Newer models DTC P1139 causes
- Defective Front oxygen (A/F) sensor #1
- Wiring or connector issues in the sensor circuit
- Faulty sensor heater circuit
- ECU (Engine Control Unit) malfunction
Subaru OBD-II 1996 & Newer models DTC P1139 seriousness
The seriousness of DTC P1139 lies in its impact on engine performance and emissions. Ignoring this issue can lead to decreased fuel efficiency and potential damage to the catalytic converter over time.
How to diagnose DTC P1139 on Subaru OBD-II 1996 & Newer models
- Use an OBD-II scanner to retrieve the fault code
- Inspect the Front oxygen (A/F) sensor #1 and its wiring for any visible damage
- Check the sensor heater circuit for continuity and proper voltage
- Perform a thorough inspection of the ECU for any signs of malfunction
How to fix DTC P1139 on Subaru OBD-II 1996 & Newer models
- Replace the Front oxygen (A/F) sensor #1 if it is found to be faulty
- Repair any damaged wiring or connectors in the sensor circuit
- If the sensor heater circuit is at fault, repair or replace as necessary
- If ECU malfunction is confirmed, consider reprogramming or replacing the ECU
How to erase DTC P1139 on Subaru OBD-II 1996 & Newer models
- Use an OBD-II scanner to clear the fault code after the underlying issue has been resolved
- Ensure that the repair has been successful by monitoring the vehicle’s performance and checking for any recurring codes
Recommended tools for Subaru OBD-II 1996 & Newer models diagnostics
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