P0131,P0137,P0151,P0157 O2 Sensor Circuit Low

P0131,P0137,P0151,P0157 O2 Sensor Circuit Low - the 4-Wire Oxygen sensor is equipped with a galvanic battery that typically generates a voltage signal between 0.0 volts and 1.0 volts. The 4-Wires O2 sensor also includes a heating element that keeps the sensor at proper operating temperature during all operating modes.

P0131 O2 Sensor Circuit Low (Bank 1 Sensor 1)

Maintaining correct sensor temperature at all times allows the system to enter into closed loop operation sooner. Also, it allows the system to remain in closed loop operation during periods of extended idle. A bias voltage in the Powertrain Control Module (PCM) shifts the signal voltage to fluctuate between 2.5 volts and 3.5 volts, depending upon the oxygen content of the exhaust gas. When a large amount of oxygent is present (caused by a lean air/fuel mixture) the sensor produces a low voltage. When there is a lesser amount of oxygen present (caused by a rich air/fuel mixture) it produces a higher voltage. By monitoring the oxygen content and converting it to electrical voltage, the sensor acts as a rich-lean switch. In open loop operation the PCM ignores input from the O2 sensors. In closed loop operation the PCM monitors the O2 sensors input (along with other inputs) and adjust the injector pulse widht accordingly based on pre-programmed (fixed) values and inputs from other sensors. The PCM also compares upstream and downstream O2 sensor inputs to calculate the catalytic converter oxygen storage capacity and converter efficiency.

When monitored engine running for less than 30 seconds, battery voltage greater 10.4 volts. Set condition, the Oxygen sensor signal voltage is below the minimum acceptable value. Deafault action, the MIL light will illuminate.

Possible causes:
  • O2 sensor return circuit shorted to ground.
  • O2 sensor signal circuit shorted to ground.
  • O2 sensor signal circuit shorted to the O2 sensor retun circuit.
  • O2 sensor signal circuit shorted to the O2 sensor heater ground circuit.
  • O2 sensor.
  • Powertrain Control Module (PCM).

Diagnose code P0131,P0137,P0151,P0157 O2 Sensor Circuit Low

Step 1. Check active DTC
Turn the ignition on, with the scan tool, read DTC and record Freeze Frame information. Start the engine and allow it to idle for at least 60 seconds.

Warning : When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

With the scan tool, read DTC.

Is the DTC active or pending?

Yes, go to step 2.
No, perform the PCM intermittent condition.

Step 2. Check the O2 sensor 1/1 signal circuit
Turn the igniton off, disconnect the O2 sensor 1/1 harness connector. Turn the ignition on, with the scan tool, monitor the O2 sensor 1/1 voltage.

Is the O2 sensor 1/1 voltage between 4.1 and 5.0 volts?

Yes, go to step 3.
No, go to step 5.

Step 3. O2 sensor 1/1
Measure the voltage on the O2 sensor 1/1 return circuit in the O2 sensor harness connector.

Is the voltage at 2.5 volts?

Yes, verify that there is good pin to terminal contact in the O2 sensor 1/1 and Powertrain Control Module (PCM) connectors. If problems are not found, replace the O2 sensor 1/1.

No, go to step 4.

Step 4. Check the O2 sensor 1/1 return circuit for a short to ground
Turn the ignition off, disconnect the PCM harness connector. Check for continuity between ground and the O2 sensor 1/1 return circuit at the O2 sensor 1/1 harness connector.

Is there continuity between ground and the O2 sensor 1/1 return circuit?

Yes, repair the O2 sensor 1/1 return circuit for a short to ground.
No, go to step 8.

Step 5. Check the O2 sensor 1/1 signal circuit for a short to ground
Turn the ignition off, disconnect the PCM harness connector. Check for continuity between ground and the O2 sensor 1/1 signal circuit at the O2 sensor 1/1 harness connector.

Is there continuity between ground and the O2 sensor 1/1 signal circuit?

Yes, repair the O2 sensor 1/1 signal circuit for a short to ground.
No, go to step 6.

Step 6. Check for the O2 sensor 1/1 signal circuit shorted to the O2 sensor 1/1 return upstream circuit
Check for continuity between the O2 sensor 1/1 signal circuit and the O2 sensor 1/1 return circuit at the O2 sensor 1/1 harness connector.

Is there continuity between the O2 sensor 1/1 signal circuit and the O2 sensor 1/1 return circuit?

Yes, repair the short between the O2 sensor 1/1 signal circuit and the O2 sensor 1/1 return circuit.
No, go to step 7.

Step 7. Check for the O2 sensor 1/1 signal circuit shorted to the O2 sensor 1/1 heater ground circuit
Check for continuity between the O2 sensor 1/1 signal circuit and the O2 sensor 1/1 heater ground circuit at the O2 sensor 1/1 harness connector.

Is there continuity between the O2 sensor 1/1 signal circuit and the O2 sensor 1/1 heater ground circuit?

Yes, repair the short between the O2 sensor 1/1 signal circuit and the O2 sensor ground heater ground circuit.

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