DTC P0138 [LF ATX (FN4A-EL), L3 ATX]

id0102b6805100

DTC P0138

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 for 0.8 s, the PCM determines that circuit input is high.
Diagnostic support note
•  This is a continues 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 is available.
•  DTC is stored in the PCM memory.
POSSIBLE CAUSE
•  HO2S malfunction
•  Short to power supply in wiring harness between HO2S terminal A and PCM terminal 2AH
•  HO2S or PCM terminal shorted
•  PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION
1
VERIFY FREEZE FRAME DATA HAVE BEEN RECORDED
•  Have 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
•  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 OR STORED DTC
•  Turn the ignition switch off, then to the ON position. (Engine off)
•  Verify pending code or stored DTCs using M-MDS.
•  Is other DTC present?
Yes
Go to the appropriate DTC troubleshooting procedures.
(See DTC TABLE [LF ATX (FN4A-EL), L3 ATX].)
No
Go to the next step.
4
IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA
•  Is DTC P0138 on FREEZE FRAME DATA?
Yes
Go to the next step.
No
Go to troubleshooting procedures for DTC on FREEZE FRAME DATA.
(See DTC TABLE [LF ATX (FN4A-EL), L3 ATX].)
5
INSPECT HO2S SIGNAL CIRCUIT FOR SHORT TO POWER SUPPLY
•  Turn the ignition switch off.
•  Disconnect HO2S connector.
•  Turn the ignition switch to the ON position. (Engine off)
•  Measure the voltage between HO2S terminal A and body ground.
•  Is there any voltage?
Yes
Replace short to power supply, then go to Step 7.
No
Go to the next step.
6
VERIFY CURRENT INPUT SIGNAL STATUS
•  Start engine.
•  Access O2S12 PID using M-MDS.
•  Verify PID while racing engine at least 10 times in NEUTRAL.
•  Does PID stay above 0.55 V?
Yes
Replace sensor, then go to the next step.
(See AIR FUEL RATIO (A/F) SENSOR, HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [LF, L3].)
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 the memory using the M-MDS.
•  Run the KOEO or KOER self‐test with M-MDS, or PCM adaptive memory procedure drive mode and HO2S heater, HO2S, and TWC repair verification drive mode.
•  Is the PENDING CODE for this DTC present?
Yes
Replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION [LF, L3].)
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.
(See DTC TABLE [LF ATX (FN4A-EL), L3 ATX].)
No
Troubleshooting completed.