DTC Troubleshooting: P2628, P2631
DTC P2628: Rear A/F Sensor (Bank 1, Sensor 1) LABEL Circuit High Voltage
DTC P2631: Front A/F Sensor (Bank 2, Sensor 1) LABEL Circuit High Voltage
NOTE:
Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.
Information marked with an asterisk (*) applies to the front bank (Bank 2).

DTC Description
Confirmed DTC
Pending DTC
Freeze Frame
P2628 Rear A/F Sensor (Bank 1, Sensor 1) LABEL Circuit High Voltage
      
P2631 Front A/F Sensor (Bank 2, Sensor 1) LABEL Circuit High Voltage
     

1.
Problem verification:

Problem verification
?1.
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 for 2 minutes.

?4.
Check for Pending or Confirmed DTCs with the HDS.
DTC Description
Confirmed DTC
Pending DTC
Freeze Frame
P2628 Rear A/F Sensor (Bank 1, Sensor 1) LABEL Circuit High Voltage
     
P2631 Front A/F Sensor (Bank 2, Sensor 1) LABEL Circuit High Voltage
      

Is DTC P2628 and/or P2631* indicated?

     
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 the A/F sensor (Sensor 1) and the PCM.?
2.
Open wire check (VLBLB1 line (VLBLB2 line)*):

Open wire check (VLBLB1 line (VLBLB2 line)*)
?1.
Press the engine start/stop button to select the OFF mode.

?2.
Jump the SCS line with the HDS.


?3.
Disconnect the following connectors.

?4.
Check for continuity between test points 1 and 2.
Test condition
OFF mode
PCM connector C (51P): disconnected
Rear A/F sensor (Bank 1, Sensor 1) 8P connector: disconnected
Front A/F sensor (Bank 2, Sensor 1) 8P connector*: disconnected
Test circuit
VLBLB1 (VLBLB2)*
Test point 1
PCM connector C (51P) No. 24 (WHT)
PCM connector C (51P) No. 27 (LT BLU)*
Test point 2
Rear A/F sensor (Bank 1, Sensor 1) 8P connector No. 6 (WHT)
Front A/F sensor (Bank 2, Sensor 1) 8P connector No. 6 (LT BLU)*


Is there continuity?

     
YES
     
     
     
Go to step 3.
     
NO
     
     
     
Repair an open in the VLBLB1 (VLBLB2)* wire between the PCM (C24 (C27)*) and the A/F sensor (Sensor 1), then do the repair verification.
3.
Open wire check (SG1 line):

Open wire check (SG1 line)
?1.
Check for continuity between test points 1 and 2.
Test condition
OFF mode
PCM connector C (51P): disconnected
Rear A/F sensor (Bank 1, Sensor 1) 8P connector: disconnected
Front A/F sensor (Bank 2, Sensor 1) 8P connector*: disconnected
Test circuit
SG1
Test point 1
PCM connector C (51P) No. 33 (BLU)
Test point 2
Rear A/F sensor (Bank 1, Sensor 1) 8P connector No. 7 (BLU)
Front A/F sensor (Bank 2, Sensor 1) 8P connector No. 7 (BLU)*


Is there continuity?

     
YES
     
     
     
Go to step 4.
     
NO
     
     
     
Repair an open in the SG1 wire between the PCM (C33) and the A/F sensor (Sensor 1), then do the repair verification.
4.
PCM internal circuit check:

PCM internal circuit check
?1.
Exit the SCS mode with the HDS.


?2.
Reconnect PCM connector C (51P).

?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 for 2 minutes.

?4.
Measure the voltage between test points 1 and 2.
Test condition
Engine running
Rear A/F sensor (Bank 1, Sensor 1) 8P connector: disconnected
Front A/F sensor (Bank 2, Sensor 1) 8P connector*: disconnected
Test circuit
VLBLB1 (VLBLB2)*
Test point 1
Rear A/F sensor (Bank 1, Sensor 1) 8P connector No. 6 (WHT)
Front A/F sensor (Bank 2, Sensor 1) 8P connector No. 6 (LT BLU)*
Test point 2
Body ground


Is there about 5.0 V?

     
YES
     
     
     
The PCM internal circuit is OK. Replace the A/F sensor (Sensor 1), then do the repair verification.
     
NO
     
     
     
Update the PCM if it does not have the latest software, or substitute a known-good PCM, then do the repair verification.
Repair verification (OBD STATUS check):

?1.
Reconnect all connectors.

?2.
Exit the SCS mode with the HDS.


?3.
Press the engine start/stop button to select the ON mode.

?4.
Reset the PCM with the HDS.


?5.
Do the PCM idle learn procedure.

?6.
Monitor the OBD STATUS for DTC P2628 and/or P2631* in the DTCs MENU with the HDS.
DTC Description
OBD STATUS
P2628 Rear A/F Sensor (Bank 1, Sensor 1) LABEL Circuit High Voltage
 
P2631 Front A/F Sensor (Bank 2, Sensor 1) LABEL Circuit High Voltage
  


Does the HDS indicate PASSED, FAILED, or NOT COMPLETED?

     
PASSED (P2628)
     
     
     
Troubleshooting is complete. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting. ?
     
PASSED (P2631)
     
     
     
Troubleshooting is complete. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting. ?
     
FAILED (P2628)
     
     
     
Go to step 1 and recheck.
     
FAILED (P2631)
     
     
     
Go to step 1 and recheck.
     
NOT COMPLETED
     
     
     
Keep idling until a result comes on.