Code Definition: Oxygen Sensor Circuit Malfunction (Bank 1, Sensor 2)
The P0135 code is a generic powertrain code that indicates a problem with the oxygen sensor circuit in bank 1, sensor 2. The oxygen sensor measures the amount of oxygen in the exhaust gases and sends a signal to the engine control module (ECM) to adjust the fuel injection accordingly. When the ECM detects a malfunction in the oxygen sensor circuit, it stores the P0135 code and illuminates the check engine light.
Possible Causes:
- Faulty oxygen sensor
- Damaged or worn-out wiring harness
- Loose or corroded electrical connections
- Malfunctioning catalytic converter
- Exhaust system leaks
- Engine running rich or lean
Symptoms:
- Check engine light illuminated
- Poor fuel economy
- Rough engine idle
- Decreased performance
- Increased emissions
Diagnostic Procedure:
- Scan the vehicle for any other codes that may be present. If there are no other codes, proceed to step 2.
- Use a scan tool to monitor the oxygen sensor voltage. The voltage should fluctuate between 0 and 450 mV depending on the engine load and fuel mixture. If the voltage remains steady at around 450 mV, it could indicate a faulty oxygen sensor.
- Inspect the wiring harness and connectors for damage or wear. Make sure all connections are secure and not loose.
- Test the oxygen sensor using a multimeter. Measure the resistance across the sensor terminals. A good oxygen sensor should have a resistance value between 7-10 ohms. If the resistance is outside this range, replace the sensor.
- If the oxygen sensor appears to be functioning properly, suspect a malfunctioning catalytic converter. Perform a visual inspection of the converter for signs of damage or clogging.
- If the catalytic converter appears to be in good condition, perform an exhaust leak test to determine if there are any leaks in the exhaust system.
- If no leaks are found, the issue may be caused by an engine mechanical problem. Consult a professional mechanic for further diagnosis.
Repair Information:
- Replace the faulty oxygen sensor. Be sure to use the correct replacement part number for your specific vehicle make and model.
- Repair any damaged or worn-out wiring harness sections.
- If the catalytic converter is malfunctioning, replace it with a new one.
- If an exhaust leak was detected, repair or replace the affected section of the exhaust system.
- Clear the DTC from the ECM after repairs are complete and take the vehicle for a test drive to ensure proper operation.
