P0137

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
In order to control emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.

The Powertrain Control Module (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 the 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).

Replace the entire HO2S 2 assembly. Do not attempt to repair the HO2S 2 if the following conditions exist:
^ Damaged wiring
^ Damaged electrical connectors
^ Damaged terminals

Obstruction of the air reference and degraded HO2S 2 performance could result from any attempt to repair the above conditions.

The HO2S 2 must have a clean air reference in order for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201 P0202, P0203, P0204, P0300, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
^ The air flow is more than 5.5 grams per second.
^ The Engine Coolant Temperature (ECT) is more than 40°C (104°F).
^ The Throttle Position (TP) angle is between 5 percent and 50 percent for 4 seconds.

CONDITIONS FOR SETTING THE DTC
The voltage reading on HO2S 2 remains below 43 mV for 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 malfunction present.
^ The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.
^ A history DTC stores.
^ The 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.
^ Use a scan tool to clear the DTCs.

DIAGNOSTIC AIDS
^ The exhaust system - Inspect the exhaust system for the following conditions.
- Exhaust system leaks between the three-way catalytic converter and the flange
- Exhaust system corrosion between the three-way catalytic converter and the flange
- Exhaust system loose or missing hardware between the three-way catalytic converter and the flange
Repair the conditions as necessary.
^ A faulty electrical connection or a damaged harness - Inspect the harness for a short to ground in the HO2S 2 signal circuit. Ensure that the HO2S 2 pigtail is not contacting the exhaust.

Check for the following conditions:
- Wiring contacting the exhaust system
- Improper mating
- Broken locks
- Improperly formed harness connectors
- Damaged terminals
- Faulty terminal-to-wire connections
- A damaged harness
^ Intermittent test - Observe the HO2S 2 on the scan tool while moving any of the related electrical connectors and the wiring harness with the ignition ON. If the malfunction is induced, the HO2S 2 display will change. This should help isolate the location of the malfunction.

An intermittent could be the result of the following conditions.
^ A faulty electrical connection
^ Rubbed-through wire insulation
^ A broken wire inside the insulation

Replace the entire HO2S 2 assembly. Do not attempt to repair the HO2S 2 if the following conditions exist:
^ Damaged wiring
^ Damaged electrical connectors
^ Damaged terminals

Obstruction of the air reference and degraded HO2S 2 performance could result from any attempt to repair the above conditions.

The HO2S 2 must have a clean air reference in order for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. In order to determine if the engine is lean during power enrichment operate the vehicle under higher throttle/acceleration conditions while monitoring scan tool O2S voltage and the power enrichment parameter. A lean condition will cause O2S voltage to be less than 598 mV during power enrichment.
5. Monitor the O2S voltage of the opposite bank sensor. If the voltage activity of the opposite bank sensor is similar to the voltage activity of the suspect sensor check for lean conditions that would affect both cylinder banks. An opposite bank sensor with normal O2S voltage activity indicates the suspect O2S needs replacement or a lean condition exists only on the suspect O2S cylinder bank.