DTC P0138 [L8, LF]

id0102b1805100

DTC P0138 | HO2S circuit high input
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DETECTION CONDITION | • The PCM monitors input voltage from HO2S. If the input voltage from the HO2S is above 1.2 V for 0.8 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 the first drive cycle. • FREEZE FRAME DATA (Mode 2/Mode 12) is available. • The DTC is stored in the PCM memory.
POSSIBLE CAUSE | • HO2S connector or terminals malfunction • PCM connector or terminals malfunction • Short to power supply in wiring harness between HO2S terminal A and PCM terminal 2Q • HO2S malfunction • PCM malfunction

Diagnostic procedure

STEP | INSPECTION | ACTION
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1 | VERIFY FREEZE FRAME DATA (MODE 12) AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED • Have the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS (A/F sensor, HO2S related) been recorded? | Yes | Go to the next step.
No | Record the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS on repair order, then go to the next step.
2 | VERIFY RELATED SERVICE INFORMATION AVAILABILITY • Verify related Service Information availability. • Is any related Service Information available? | Yes | Perform repair or diagnosis according to the available Service Information. • If the vehicle is not repaired, go to the next step.
No | Go to the next step.
3 | VERIFY RELATED PENDING CODE AND STORED DTC • Turn the ignition switch off, then to the ON position. (engine off) • Perform the Pending Trouble Code Access Procedure and DTC Reading Procedure. (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) • Are any DTCs present? | Yes | Go to the applicable DTC troubleshooting. (See DTC TABLE [L8, LF].)
No | Go to the next step.
4 | IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA (MODE 2) • Perform the Freeze Frame PID Data Access Procedure. (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) • Is the DTC P0138 on FREEZE FRAME DATA (Mode 2)? | Yes | Go to the next step.
No | Go to the DTC troubleshooting on FREEZE FRAME DATA (Mode 2). (See DTC TABLE [L8, LF].)
5 | INSPECT HO2S CONNECTOR AND TERMINALS • Turn the ignition switch off. • Disconnect the HO2S connector. • Inspect for poor connection (such as damaged/pulled-out pins, and corrosion). • Is there any malfunction? | Yes | Repair or replace the connector or terminals, then go to Step 9.
No | Go to the next step.
6 | INSPECT PCM CONNECTOR AND TERMINALS • Disconnect the PCM connector. • Inspect for poor connection (such as damaged/pulled-out pins, and corrosion). • Is there any malfunction? | Yes | Repair or replace the connector or terminals, then go to Step 9.
No | Go to the next step.
7 | INSPECT HO2S SIGNAL CIRCUIT FOR SHORT TO POWER SUPPLY • HO2S and PCM connectors are disconnected. • Turn the ignition switch to the ON position. (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 possible short to power supply, then go to Step 9.
No | Go to the next step.
8 | INSPECT HO2S • Turn the ignition switch off. • Reconnect the HO2S and PCM connectors. • Inspect the HO2S. (See HEATED OXYGEN SENSOR (HO2S) INSPECTION [L8, LF].) • Is there any malfunction? | Yes | Replace sensor, then go to the next step. (See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [L8, LF].)
No | Go to the next step.
9 | VERIFY DTC TROUBLESHOOTING COMPLETED • Make sure to reconnect all disconnected connectors. • Turn the ignition switch to the ON position. (engine off) • Clear the DTC from the PCM memory using the M-MDS. (See AFTER REPAIR PROCEDURE [L8, LF].) • Perform the KOEO/KOER self test. (See KOEO/KOER SELF TEST [L8, LF].) • Is the PENDING CODE for this DTC present? | Yes | Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [L8, LF].)
No | Go to the next step.
10 | VERIFY AFTER REPAIR PROCEDURE • Perform the “AFTER REPAIR PROCEDURE”. (See AFTER REPAIR PROCEDURE [L8, LF].) • Are any DTCs present? | Yes | Go to the applicable DTC troubleshooting. (See DTC TABLE [L8, LF].)
No | DTC troubleshooting completed.