P0137

DTC P0137 Downstream Heated Oxygen Sensor Bank 1 Low Voltage

Wiring Diagram:

Circuit Description

The engine control module (ECM) supplies a voltage of about 0.45 V between the ECM terminals 27 and 67. The oxygen (O2) sensor varies the voltage within a range of about 1 V if the exhaust is rich, down to about 0.1 V if the exhaust is lean. The O2 sensor is like an open circuit and produces no voltage when it is below 360 °C (600 °F). An open O2 sensor circuit or a cold O2 sensor causes "open loop" operation.

Conditions for Setting the DTC

(Case A)
- The engine controls system is in closed loop.
- Engine speed is less than 6,000 rpm.
- The heated oxygen sensor voltage is below 0.1 V for at least 20 seconds.
- No relevant DTCs are set.

(Case B)
- The engine controls system is in full fuel cut off.
- Engine speed is less than 6,000 rpm.
- The heated oxygen sensor voltage is between 0.352 and 0.499 at least 20 seconds.
- No relevant DTCs are set.

Action Taken When the DTC Sets

- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fail. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC

- The MIL will turn off at the end of three (3) consecutive validation cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids

- Normal scan tool voltage varies between 0.1 volts and 0.9 volts while in closed loop.
- Inspect the oxygen (O2) sensor wire. The O2 sensor may be positioned incorrectly and contacting the exhaust manifold.
- Check for an intermittent ground in the wire between the O2 sensor and the engine control module.
- Perform an injector balance test to determine if a restricted fuel injector may be causing the lean condition.
- Vacuum of crankcase leaks will cause a lean running condition.
- An exhaust manifold gasket leak of a cracked exhaust manifold may cause outside air to be pulled into the exhaust and past the sensor.

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Step 8 - 10:

DTC P0137 - Downstream Heated Oxygen Sensor Bank 1 Low Voltage