DTC P0138:00

DTC P0138:00	HO2S circuit high input
DETECTION CONDITION	The PCM monitors input voltage from HO2S. If the input voltage from the HO2S is above 1.2 V or HO2S bias voltage above 1.7 V for 5 s , the PCM determines that circuit input is high. Diagnostic support note This is a continuous monitor (A/F sensor, HO2S). 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. PENDING CODE is available if the PCM detects the above malfunction condition during first drive cycle. FREEZE FRAME DATA (Mode 2)/Snapshot data is available. The DTC is stored in the PCM memory.
POSSIBLE CAUSE	HO2S connector or terminals malfunction PCM connector or terminals malfunction HO2S circuits are shorted to each other Short to power supply in wiring harness between HO2S terminal A and PCM terminal 2Q HO2S malfunction PCM malfunction

DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA (MODE 2) Perform the Freeze Frame PID Data Access Procedure. (See ON-BOARD DIAGNOSTIC TEST ). Is the DTC P0138:00 on FREEZE FRAME DATA (Mode 2)?	Yes	Go to the next step.
1		No	Go to the troubleshooting procedures for DTC on FREEZE FRAME DATA (Mode 2). (See DTC TABLE ).
2	VERIFY FREEZE FRAME DATA (MODE 2)/SNAPSHOT DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED Have the FREEZE FRAME DATA (Mode 2)/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS (A/F sensor, HO2S related) been recorded?	Yes	Go to the next step.
2		No	Record the FREEZE FRAME DATA (Mode 2)/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
3	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Verify related Service Bulletins and/or on-line repair information availability. Is any related repair information available?	Yes	Perform repair or diagnosis according to the available repair information. If the vehicle is not repaired, go to the next step.
3		No	Go to the next step.
4	VERIFY RELATED PENDING CODE AND STORED DTC Switch the ignition to off, then to ON (engine off). Perform the DTC Reading Procedure and Pending Trouble Code Access Procedure. (See ON-BOARD DIAGNOSTIC TEST ). Are any other DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE ).
4		No	Go to the next step.
5	INSPECT HO2S CONNECTOR CONDITION Switch the ignition to off. Disconnect the HO2S connector. Inspect for poor connection (such as damaged/pulled-out pins, corrosion). Is there any malfunction?	Yes	Repair or replace the terminal and/or connector, then go to Step 10.
5		No	Go to the next step.
6	INSPECT PCM CONNECTOR CONDITION Disconnect the PCM connector. Inspect for poor connection (such as damaged/pulled-out pins, corrosion). Is there any malfunction?	Yes	Repair or replace the terminal and/or connector, then go to Step 10.
6		No	Go to the next step.
7	INSPECT HO2S CIRCUIT FOR SHORT TO EACH OTHER HO2S and PCM connectors are disconnected. Inspect for continuity between HO2S terminal A and B (wiring harness-side). Is there continuity?	Yes	Repair or replace the malfunctioning wiring harness, then go to Step 10.
7		No	Go to the next step.
8	INSPECT HO2S SIGNAL CIRCUIT FOR SHORT TO POWER SUPPLY HO2S and PCM connectors are disconnected. Switch the ignition to ON (engine off). Measure the voltage between HO2S terminal A (wiring harness-side) and body ground. Is there any voltage?	Yes	Repair or replace the wiring harness for a short to power supply, then go to Step 10.
8		No	Go to the next step.
9	INSPECT HO2S Reconnect the HO2S and PCM connectors. Inspect the HO2S. (See HEATED OXYGEN SENSOR (HO2S) INSPECTION ). Is there any malfunction?	Yes	Replace the HO2S, then go to the next step. (See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION ).
9		No	Go to the next step.
10	VERIFY DTC TROUBLESHOOTING COMPLETED Make sure to reconnect all disconnected connectors. Clear the DTC from the PCM memory using the M-MDS. (See AFTER REPAIR PROCEDURE ). Perform the KOEO or KOER self test.	Yes	Repeat the inspection from Step 1. If the malfunction recurs, replace the PCM. (See PCM REMOVAL/INSTALLATION ). Go to the next step.
10		No	Go to the next step.
11	VERIFY AFTER REPAIR PROCEDURE Perform the "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE ). Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE ).
11		No	DTC troubleshooting completed.