P0138
CIRCUIT DESCRIPTIONIn 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 heated oxygen sensor (HO2S 1).
Do not attempt to repair the HO2S 2. Replace the entire HO2S 2 assembly if the following conditions exist:
^ Damaged wiring
^ Damaged electrical connector
^ Damaged terminals
Obstruction of the air reference and degraded HO2S 2 performance could result in 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, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0336, P0440, P0446, P0452, P0453, P0507, P0601, P0602, P0604, P0606, P1120, P1220, P1221, P1271, P1275, P1280, P1484, P1512, P1514, P1515, P1516, P1621, P1635, P1639, P1680, or P1681 are not set.
^ The fuel level sensor is more than 10 percent.
^ The ignition 1 signal is more than 10 volts.
^ The engine coolant temperature (ECT) is more than 70°C (158°F).
^ The throttle position (TP) indicated angle is between 15-50 percent for 3.8 seconds.
^ The accelerator pedal position (APP) indicated angle is more than 1.2 percent.
^ The manifold absolute pressure (MAP) is more than 25 kPa.
^ The above conditions have been met for 3.8 seconds.
CONDITIONS FOR SETTING THE DTC
The HO2S 2 voltage is more than 1042 mV for 50 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/Failure Records buffers.
^ A history DTC stores.
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
Check for the following conditions:
^ A rich exhaust-An overly rich exhaust may load the catalyst causing high HO2S 2 signal voltages.
^ Silicone contamination-Silicone contamination of HO2S 2 could cause a false rich condition. A powdery white deposit on the sensor will indicate this condition.
TEST
