DTC P0138 [LF, L3]

id0102008051a3

DTC P0138

Rear HO2S circuit high input

DETECTION CONDITION

• The PCM monitors the input voltage from the rear HO2S. If the input voltage from the rear HO2S sensor is above 0.45 V for 7 s during deceleration fuel cut, the PCM determines that the circuit input is high.
Diagnostic support note
• This is a continuous monitor (CCM).
• The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
• The PENDING CODE is available if the PCM detects the above malfunction condition during the first drive cycle.
• The FREEZE FRAME DATA is available.
• The DTC is stored in the PCM memory.

POSSIBLE CAUSE

• Rear HO2S malfunction
• Short to power circuit in wiring harness between rear HO2S terminal A and PCM terminal 1Y

Diagnostic procedure

STEP

INSPECTION

ACTION

1
VERIFY FREEZE FRAME DATA HAS BEEN RECORDED
• Has the FREEZE FRAME DATA been recorded?
Yes
Go to the next step.
No
Record the FREEZE FRAME DATA on repair order, then go to the next step.
2
VERIFY RELATED SERVICE INFORMATION AVAILABILITY
• Check for related Service Information availability.
• Is any related Service Information available?
Yes
Perform repair or diagnosis according to available Service Information.
• If the vehicle is not repaired, go to the next step.
No
Go to the next step.
3
VERIFY RELATED PENDING OR STORED DTCS
• Turn the ignition switch to the OFF position, then ON (Engine off).
• Verify pending code or stored DTCs using the WDS or equivalent.
• Are any other DTCs present?
Yes
Go to the appropriate DTC troubleshooting procedures.
No
Go to the next step.
4
IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA
• Is DTC P0138 displayed in the FREEZE FRAME DATA?
Yes
Go to the next step.
No
Go to the troubleshooting procedures for the DTC displayed in the FREEZE FRAME DATA.
5
INSPECT REAR HO2S SIGNAL CIRCUIT FOR SHORT TO POWER SUPPLY CIRCUIT
• Turn the ignition switch to the OFF position.
• Disconnect rear HO2S connector.
• Turn the ignition switch to the ON position (Engine off).
• Measure the voltage between rear HO2S terminal A (harness-side) and body ground.
• Is there any the voltage reading?
Yes
Replace for a short to power supply, then go to Step 7.
No
Go to the next step.
6
VERIFY CURRENT INPUT SIGNAL STATUS
• Start the engine.
• Access the O2S12 PID using the WDS or equivalent.
• Verify the PID while racing the engine at least 10 times (in NEUTRAL (MTX) or PARK (ATX)).
• Does the PID reading stay above 0.45 V?
Yes
Repair or replace the sensor, then go to the next step.
No
Go to the next step.
7
VERIFY TROUBLESHOOTING OF DTC P0138 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Turn the ignition switch to the ON position (Engine off).
• Clear the DTC from memory using the WDS or equivalent.
• Run the PCM adaptive memory procedure drive mode and the HO2S heater, HO2S, and TWC repair verification drive modes.
• Is the PENDING CODE the same as the DTC present?
Yes
Replace the PCM, then go to the next step.
No
Go to the next step.
8
VERIFY AFTER REPAIR PROCEDURE
• Perform the "After Repair Procedure".
• Are any DTCs present?
Yes
Go to the applicable DTC troubleshooting.
No
Troubleshooting completed.