DTC P0138 [L3]

BME010200100W18

DTC P0138

Rear HO2S circuit high input

DETECTION CONDITION

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

POSSIBLE CAUSE

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

Diagnostic procedure

STEP

INSPECTION

ACTION

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