Diagnostic Aids
- A DTC P0134 can set when the vehicle runs out of fuel. Ask the vehicle operator if the vehicle has recently been run out of fuel.
- The scan tool output control feature, Fuel Injector Modification, can be used at idle to check the oxygen sensor performance. Increasing the Fuel Injector Modification Commanded State to 25 percent should cause the HO2S 1 voltage to exceed 800 mV. Decreasing the Fuel Injector Modification Commanded State to -12 percent should cause the HO2S 1 voltage to drop to less than 100 mV. An oxygen sensor that fails to respond accordingly may be faulty or contaminated. When performing a Fuel Injector Modification with the scan tool, the Loop Status will remain Open Loop and the Short Term FT will be fixed at 0 percent.
- If a DTC P0134 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance Heated Oxygen Sensor/Oxygen Sensor System Set .
- Check for any of the following conditions:
- A misrouted heated oxygen sensor wiring-The sensor pigtail may be misrouted and contacting the exhaust system causing a short to ground.
- Verify the PCM to engine electrical grounds are OK.
- An incorrect fuel pressure-The fuel system can go lean if the fuel pressure is too low and DTC P0134 may be set. Refer to Fuel System Diagnosis .
- An incorrectly calibrated fuel injector
- Any vacuum leaks-Inspect for disconnected or damaged vacuum hoses and for vacuum leaks at the intake manifold, the throttle body, and the crankcase ventilation system.
- Any exhaust leaks near the HO2S-An exhaust leak may cause outside air to be pulled into the exhaust gas stream and past the HO2S. The outside air may cause DTC P0134 to set.
- A shorted HO2S-An HO2S that is shorted to ground will display less than 0.1 volt on the scan tool. An HO2S that is shorted to voltage will display a reading of more than 1.0 volt on the scan tool. Water contamination of the HO2S can cause a low or high HO2S voltage to be indicated. A DTC P0134 that occurs more frequently when driving through standing water or when operating the vehicle in wet driving conditions can indicate water intrusion. Replace the HO2S if the sensor is adversely affected by moisture.
- A contaminated HO2S-Silicon contamination of the HO2S can cause a low signal voltage to be indicated. Silicon contamination is indicated by a powdery white deposit on the portion of the HO2S exposed to the exhaust stream. Before replacing the HO2S, determine the cause of the contamination and correct the condition.
- Fuel contamination-Small amounts of water can be delivered to the fuel injectors and cause a lean exhaust indication. A lean exhaust indication can also be caused by too much alcohol in the fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- A faulty electrical connection to the PCM
- An intermittent malfunction may be caused by a fault in the HO2S 1 electrical circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .
- Repair any electrical circuit faults that were found. Refer to Wiring Repairs .
- The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.