DTC Troubleshooting: P0138 (63)
DTC P0138:
 Secondary HO2S (Sensor 2) Circuit High Voltage
NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.
  1. Turn the ignition switch ON (II).
  1. Clear the DTC with the HDS.
  1. Start the engine. Hold the engine speed at 3,000 rpm (min −1 ) without load (in neutral) until the radiator fan comes on, then let it idle.
  1. Check the HO2S S2 in the DATA LIST with the HDS.
Does the voltage stay at 1.25 V or more?
YES -
Go to Step 5 .
NO -
Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the ECM.■
  1. Turn the ignition switch OFF.
  1. Disconnect the secondary HO2S (Sensor 2) 4P connector.
  1. Connect secondary HO2S (Sensor 2) 4P connector terminals No. 1 and No. 2 with a jumper wire.
  1. Turn the ignition switch ON (II).
  1. Check the HO2S S2 in the DATA LIST with the HDS.
Does the voltage stay at 1.25 V or more?
YES -
Go to Step 10 .
NO -
Go to Step 19 .
  1. Turn the ignition switch OFF.
  1. Remove the jumper wire from the secondary HO2S (Sensor 2) 4P connector.
  1. Connect secondary HO2S (Sensor 2) 4P connector terminal No. 1 to body ground with a jumper wire.
  1. Turn the ignition switch ON (II).
  1. Check the HO2S S2 in the DATA LIST with the HDS.
Does the voltage stay at 1.25 V or more?
YES -
Go to Step 15 .
NO -
Repair open in the wire between the ECM (B33) and the secondary HO2S (Sensor 2), then go to Step 21 .
  1. Turn the ignition switch OFF.
  1. Jump the SCS line with the HDS.
  1. Disconnect ECM connector C (44P).
  1. Check for continuity between ECM connector terminal C27 and body ground.
Is there continuity?
YES -
Go to Step 29 .
NO -
Repair open in the wire between the ECM (C27) and the secondary HO2S (Sensor 2), then go to Step 21 .
  1. Turn the ignition switch OFF.
  1. Reconnect all connectors and the battery.
  1. Turn the ignition switch ON (II).
  1. Reset the ECM with the HDS.
  1. Start the engine. Hold the engine speed at 3,000 rpm (min −1 ) without load (in neutral) until the radiator fan comes on, then let it idle.
  1. Test-drive under these conditions:
    • Engine coolant temperature (ECT SENSOR 1) above 80 °C (176 °F)
    • Transmission in 4th gear
    • Engine speed between 1,500−3,000 rpm (min −1 )
    • Drive about 1 minute or more
  1. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0138 indicated?
YES -
Check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the ECM, then go to Step 1 .
NO -
Go to Step 28 .
  1. Monitor the OBD STATUS for DTC P0138 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES -
Troubleshooting is complete. If any other Temporary DTCs or DTCs ware indicated in Step 27 , go to the indicated DTC's troubleshooting.■
NO -
If the screen indicates FAILED, check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the ECM, then go to Step 1 . If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, go to Step 25 .
  1. Reconnect all connectors.
  1. Start the engine. Hold the engine speed at 3,000 rpm (min −1 ) without load (in neutral) until the radiator fan comes on, then let it idle.
  1. Test-drive under these conditions:
    • Engine coolant temperature (ECT SENSOR 1) above 80 °C (176 °F)
    • Transmission in 4th gear
    • ENGINE SPEED between 1,500−3,000 rpm (min −1 )
    • Drive about 1 minute or more
  1. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0138 indicated?
YES -
Check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the ECM. If the ECM was updated, substitute a known-good ECM, then go to Step 31 . If the ECM was substituted, go to Step 1 .
NO -
Go to Step 34 .
  1. Monitor the OBD STATUS for DTC P0138 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES -
If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM. If any other Temporary DTCs or DTCs were indicated in Step 33 , go to the indicated DTC's troubleshooting.■
NO -
If the screen indicates FAILED, check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the ECM. If the ECM was updated, substitute a known-good ECM, then go to Step 31 . If the ECM was substituted, go to Step 1 . If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, go to Step 31 .