P0137
P0137 O2 Bank 1 Sensor 2 Low Voltage
Circuit Description
In order to control emissions, a catalytic converter is used to convert harmful emissions into harmless water vapor and carbon dioxide.
The powertrain control module (PCM)/engine control module (ECM) has the ability to monitor this process by using a Heated Oxygen Sensor (HO2S). The HO2S, located in the exhaust stream past the catalytic converter produces an output signal which indicates the storage capacity of the catalyst; this in turn indicates the catalyst's ability to convert exhaust emissions effectively. If the catalyst is functioning properly, the HO2S signal will be far less active than the signal produced by the Oxygen Sensor (O2S).
If the HO2S pigtail wiring, connector or terminal are damaged, the entire HO2S assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have a clean air reference provided to it. This clean air reference is obtained by way of the HO2S wire(s). Any attempt to repair the wires, connector or terminals could result in the obstruction of the air reference and degrade the HO2S performance.
Conditions for Setting the DTC
- HO2S voltage is less than 0.053 volt or less than 0.422 volt in Power Enrichment (PE) mode.
- Closed loop stoichiometry.
- Engine coolant temperature (ECT) is greater than 140 °F (60 °C).
- Air/fuel ratio is between 14.5:1 and 14.8:1.
- Throttle Position Sensor is between 5% and 50% or in Power Enrichment (PE) mode.
- 2 second delay after the conditions have been met.
- No related malfunctions (see P0131).
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM/ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history Diagnostic Trouble Code (DTC) is stored.
Conditions for Clearing the MIL/DTC
- The MIL will turn off after three consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
An intermittent may be caused by rubbed-through wire insulation or a wire contacting the exhaust.
Check for the following conditions:
- Exhaust system - Inspect the exhaust system for leaks. Check the exhaust between the three-way catalytic converter and the flange for leaks, corrosion, or for loose or missing hardware and repair as necessary.
- Poor connection or damaged harness - Ensure that the HO2S pigtail is not contacting the exhaust. Check for the following conditions:
- Improper mating
- Broken locks
- Improperly formed
- Damaged terminals
- Poor terminal-to-wire connection
- Damaged harness
- Intermittent test - Observe the HO2S on the scan tool while moving related connections and wiring harness with the ignition ON. If the failure is induced, the HO2S display will change. This may help isolate the location of the malfunction.
Step 1 - 4:
Step 5 - 9:
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
2. This step determines if DTC P0137 is the result of a hard failure or an intermittent condition.
4. Jumping the HO2S low circuit, terminal A to ground is necessary to allow the PCM/ECM to display the supplied bias voltage. If the voltage is between 0.35 and 0.55 volt, then the wiring and PCM/ECM are OK.
6. The replacement PCM/ECM must be reprogrammed. Refer to the latest Techline procedure for PCM/ECM reprogramming.