P0137

CIRCUIT DESCRIPTION
The HO2S 1 produces an output signal which indicates the amount of oxygen present in the exhaust gas entering the three-way catalytic converter. The HO2S 2 produces an output signal which indicates the oxygen storage capacity of the catalyst, this in turn indicates the catalyst's ability to convert exhaust gases efficiently. If the catalyst is operating efficiently, the HO2S 1 signal will be tar more active than that produced by the HO2S 2. If the HO2S 2 signal voltage remains excessively low for an extended period of time, DTC P0137 will be set.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P01 17, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0440, P0410, P0440, P0442, P0443, P0446, P0449, P1441 are not set.
^ Closed loop commanded air/fuel ratio is between 14.5-14.8.
^ Throttle angle is between 3-35 percent.

CONDITIONS FOR SETTING THE DTC
HO2S 2 signal voltage remains below 10 mV during normal closed loop operation.

OR

^ HO2S 2 signal voltage remains below 600 mV during power enrichment mode fuel control operation
^ The condition is present for up to 5 minutes.

ACTION TAKEN WHEN THE DTC SETS
^ First failure:
- The MIL is not turned ON.
- A DTC is stored in memory under Failed Last Test.
- The Failure Records are stored.
^ Second consecutive drive cycle with a failure:
- The MIL is turned ON.
- A DTC is stored in memory under history.
- The Freeze Frame data is stored.
- The Failure Records are stored.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after the third consecutive trip the diagnostic has run and passed.
^ The history DTC will clear if the fault conditions have not been detected for 40 warm-up cycles.
^ A scan tool can be used to clear DTC information.

DIAGNOSTIC AIDS
Check for the following conditions
^ Heated oxygen sensor wiring-The sensor pigtail may be mispositioned and contacting the exhaust system.
^ Poor PCM to engine grounds-Refer to (2000 C-Car) Computer and Control Systems (PCM Power and Ground).
^ Fuel pressure-A condition which causes a lean exhaust can cause DTC P0137 to set. The system will go lean if pressure is too low. The PCM can compensate for some decrease. However, if fuel pressure is too low, a DTC P0137 may be set.
^ Fuel injectors-Refer to Fuel Injector Coil Test. Component Tests and General Diagnostics
^ Vacuum leaks-Check for the following conditions:
- Disconnected or damaged vacuum hoses- Refer to Emission Hose Routing Diagram.
- Incorrectly installed or malfunctioning crankcase ventilation valve.
- Vacuum leaks at the throttle body, EGR valve, and intake manifold mounting surfaces.
^ Exhaust leaks-An exhaust leak may cause outside air to be pulled into the exhaust gas stream past the HO2S, causing the DTC P0137 to set. Check for exhaust leaks near the HO2S 2.
^ Mass Air Flow (MAF) sensor-Disconnect the MAF sensor and see if the condition is corrected. If so, replace MAF sensor. Refer to Mass Air Flow (MAF) Sensor Replacement.
^ Fuel contamination-Water, even in small amounts, can be delivered to the fuel injectors. The water can cause a lean exhaust to be indicated. Excessive alcohol in the fuel can also cause this condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool). Component Tests and General Diagnostics Component Tests and General Diagnostics

TEST DESCRIPTION

Steps 1-8:

The number below refers to the step number on the diagnostic table.
3. DTC P0137 failing during power enrichment operation (TP angle above 60 percent) may indicate a condition described in Diagnostic Aids. If the DTC P0137 test passes while the Failure Records conditions are being duplicated, an intermittent condition is indicated. Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.