DTC Troubleshooting: P0138
DTC P0138: Secondary HO2S (Sensor 2) Circuit High Voltage
NOTE: Before you troubleshoot, 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 vehicle to the ON mode.

?2.
Clear the DTC with the HDS.


?3.
Start the engine.

?4.
Hold the engine speed at 3,000 rpm without load (CVT in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.
Signal
Current conditions
Values
Unit
ECT SENSOR 1
    
ENGINE SPEED
    

?5.
Check the parameter(s) below with the HDS.
Signal
Threshold
Current conditions
Values
Unit
Values
Unit
HO2S S2
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. If the freeze data/on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the freeze data/on-board snapshot.?
2.
Determine possible failure area (secondary HO2S (Sensor 2), others):

Determine possible failure area (secondary HO2S (Sensor 2), others)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
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
Terminal B
Secondary HO2S (Sensor 2) 4P connector No. 2


?4.
Turn the vehicle to the ON mode.

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

Do the current condition(s) match the threshold?

     
YES
     
     
     
Go to step 3.
     
NO
     
     
     
3.
Open wire check (SO2SG line):

Open wire check (SO2SG line)
?1.
Turn the vehicle to the OFF (LOCK) 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
Terminal B
Body ground


?4.
Turn the vehicle to the ON mode.

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

Do the current condition(s) match the threshold?

     
YES
     
     
     
The SO2SG wire is OK. Go to step 4.
     
NO
     
     
     
Repair an open in the SO2SG wire between the PCM (C39) and secondary HO2S (Sensor 2).?
4.
Open wire check (SO2 line):

Open wire check (SO2 line)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Jump the SCS line with the HDS.


?3.
Disconnect the following connector.
PCM connector C (51P)

?4.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
 
Secondary HO2S (Sensor 2) 4P connector: disconnected
 
Secondary HO2S (Sensor 2) 4P connector No. 1: jumped to body ground
 
PCM connector C (51P): disconnected
Test point 1
PCM connector C (51P) No. 38
Test point 2
Body ground

Is there continuity?

     
YES
     
     
     
The SO2 wire is OK. Update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If DTC P0138 goes away and the PCM was updated, troubleshooting is complete. If DTC P0138 goes away and the PCM was substituted, replace the original PCM.?
     
NO
     
     
     
Repair an open in the SO2 wire between the PCM (C38) and secondary HO2S (Sensor 2).?