P0137

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

In order to control emissions, a catalytic converter is used to convert harmful exhaust emissions into harmless water vapor and carbon dioxide.

The PCM has the capability to monitor this process by using a Rear Heated Oxygen Sensor (HO2S 2). The HO2S 2, 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 2 signal will be far less active than the signal produced by the front Oxygen Sensor (O2S 1).

If the oxygen sensor pigtail wiring, connector or terminal are damaged, the entire oxygen sensor 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 oxygen sensor wire(s). Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degrade oxygen sensor performance.

CONDITIONS FOR SETTING THE DTC

^ DTCs P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0301, P0302, P0303, P0304, P0506, P0507, P1406, P1441 not set.

^ Engine run time is greater than 25 seconds.

^ Engine Coolant Temperature (ECT) is greater than 40°C (104°F).

^ Air/fuel ratio is between 14.5:1 and 14.7:1.

^ Throttle Position (TP) angle is between 8 % and 50 % (manual trans.).

Or

^ Throttle Position (TP) angle is between 5 % and 50 % (auto trans.).

^ Engine has met the above conditions for 140 seconds.

^ HO2S 2 remains below 43 mV for up to 150 seconds.

ACTION TAKEN WHEN THE DTC SETS

^ The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.

^ The PCM 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 DTC is stored.

^ Coolant fan turns ON.

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 three way catalytic converter and flange for leaks, corrosion, or for loose or missing hardware and repair as necessary.

^ Poor connection or damaged harness - Inspect the harness for a short to ground in CKT 1668. Ensure that the HO2S 2 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 HO2S 2 on scan tool while moving related connectors and wiring harness with the ignition ON. If the failure is induced, the HO2S 2 display will change. This may help isolate the location of the malfunction.

TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Powertrain OBD 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 fault 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 CKT 1669 to ground is necessary to allow the PCM to display the supplied bias voltage. If the voltage is between 0.35 and 0.55 volt, then the wiring and PCM are OK.

6. Replacement PCM's must be reprogrammed. Refer to the latest Techline information for programming procedures.