DTC Troubleshooting: P0138
DTC P0138: Secondary HO2S (Sensor 2) Circuit High Voltage
Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.

DTC Description
Confirmed DTC
Pending DTC
Freeze Frame
P0138 Secondary HO2S (Sensor 2) Circuit High Voltage
      

1.
Problem verification:

Problem verification
?1.
Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.

?2.
Clear the DTC with the HDS.


?3.
Start the engine. Hold the engine speed at 3,000 rpm without load (A/T in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.
Signal
Current conditions
Values
Unit
ENGINE SPEED
    
ECT SENSOR 1
    

?4.
Check the parameter(s) below with the HDS.
Signal
Threshold
Current conditions
Values
Unit
Values
Unit
HO2S S2 OUTPUT VOLTAGE
More than 1.27
V
    

Do the current condition(s) match the threshold?

     
YES
     
     
     
The failure is duplicated. Go to step 2.
     
NO
     
     
     
Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at secondary HO2S (Sensor 2) and the PCM.?
2.
Determine possible failure area (Secondary HO2S (Sensor 2), others):

Determine possible failure area (Secondary HO2S (Sensor 2), others)
?1.
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.

?2.
Disconnect the following connector.

?3.
Connect terminals A and B with a jumper wire.
Terminal A
Secondary HO2S (Sensor 2) 4P connector No. 1 (ORN)
Terminal B
Secondary HO2S (Sensor 2) 4P connector No. 2 (WHT)


?4.
Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.

?5.
Check the parameter(s) below with the HDS.
Signal
Threshold
Current conditions
Values
Unit
Values
Unit
HO2S S2 OUTPUT VOLTAGE
More than 1.27
V
    

Do the current condition(s) match the threshold?

     
YES
     
     
     
Go to step 3.
     
NO
     
     
     
3.
Open wire check (SO2 line):

Open wire check (SO2 line)
?1.
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.

?2.
Remove the jumper wire from the secondary HO2S (Sensor 2) 4P connector.

?3.
Connect terminals A and B with a jumper wire.
Terminal A
Secondary HO2S (Sensor 2) 4P connector No. 1 (ORN)
Terminal B
Body ground


?4.
Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.

?5.
Check the parameter(s) below with the HDS.
Signal
Threshold
Current conditions
Values
Unit
Values
Unit
HO2S S2 OUTPUT VOLTAGE
More than 1.27
V
    

Do the current condition(s) match the threshold?

     
YES
     
     
     
Repair an open in the SO2 wire between the PCM (C38) and secondary HO2S (Sensor 2), then do the repair verification.
     
NO
     
     
     
The SO2 wire is OK. Go to step 4.
4.
Open wire check (SO2 SG/SO2SG line):

Open wire check (SO2 SG/SO2SG line)
?1.
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.

?2.
Remove the jumper wire from the secondary HO2S (Sensor 2) 4P connector.

?3.
Connect terminals A and B with a jumper wire.
Terminal A
Secondary HO2S (Sensor 2) 4P connector No. 2 (WHT)
Terminal B
Body ground


?4.
Jump the SCS line with the HDS.


?5.
Disconnect the following connector.

?6.
Check for continuity between test points 1 and 2.
Test condition
IG LOCK (0) or OFF mode
 
Secondary HO2S (Sensor 2) 4P connector terminal No. 2: jumped to body ground
 
PCM connector C (51P): disconnected
Test circuit
SO2SG
Test point 1
PCM connector C (51P) No. 39 (GRN/BLK)
Test point 2
Body ground


Is there continuity?

     
YES
     
     
     
The SO2 SG/SO2SG wire is OK. Update the PCM if it does not have the latest software, or substitute a known-good PCM, then do the repair verification.
     
NO
     
     
     
Repair an open in the SO2 SG/SO2SG wire between the PCM (C38) and secondary HO2S (Sensor 2), then do the repair verification.
Repair verification (OBD STATUS check):

?1.
Reconnect all connectors.

?2.
Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.

?3.
Exit the SCS mode with the HDS.


?4.
Reset the PCM with the HDS.


?5.
Do the PCM idle learn procedure.

?6.
Start the engine, and let it idle without load (A/T in P or N, M/T in neutral) until the radiator fan comes on.

?7.
Test-drive under these conditions:
Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
A/T in D, M/T in 3rd or 4th
Engine speed between 1,500?3,000 rpm
Drive 5 seconds or more

Signal
Current conditions
Values
Unit
ECT SENSOR 1
    
ENGINE SPEED
    

?8.
Monitor the OBD STATUS for DTC P0138 in the DTCs MENU with the HDS.
DTC Description
OBD STATUS
P0138 Secondary HO2S (Sensor 2) Circuit High Voltage
  


Does the HDS indicate PASSED, FAILED, EXECUTING, or OUT OF CONDITION?

     
PASSED
     
     
     
Troubleshooting is complete. If the PCM was substituted, replace the original PCM. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.?
     
FAILED
     
     
     
Go to step 1 and recheck. If the PCM was updated, substitute a known-good PCM, then check the OBD STATUS again.
     
EXECUTING
     
     
     
Keep the test condition until a result comes on.
     
OUT OF CONDITION
     
     
     
Meet the test condition, and check the OBD STATUS again.