DTC P0657: A/F Sensor Relay Circuit Malfunction

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).

Turn the ignition switch ON (II).
Clear the DTC with the HDS.
Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?
1. YES - Go to step 4.
2. NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the PCM, the A/F sensor relay, and the No. 9 LAFHT (15 A) fuse in the under-hood subfuse box.
Turn the ignition switch OFF.
Jump the SCS line with the HDS.
Disconnect PCM connector B (56P).
Remove the A/F sensor relay (A).

Fig 1: Removing A/F Sensor Relay
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Connect A/F sensor relay 4P connector terminal No. 3 and body ground with a jumper wire.

Fig 2: Connecting A/F Sensor Relay 4P Connector Terminal 3 And Body Ground With Jumper Wire
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Check for continuity between PCM connector terminal B10 and body ground.

Fig 3: Checking Continuity Between PCM Connector Terminal B10 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Go to step 10.
2. NO - Repair open in the wire between the PCM (B10) and the A/F sensor relay, then go to step 12.
Check for continuity between PCM connector terminal B10 and body ground.

Fig 4: Checking Continuity Between PCM Connector Terminal B10 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Repair short in the wire between the PCM (B10) and the A/F sensor relay, then go to step 12.
2. NO - Go to step 11.
Measure voltage between A/F sensor relay 4P connector terminal No. 4 and body ground.

Fig 5: Measuring Voltage Between A/F Sensor Relay 4P Connector Terminal 4 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage
1. YES - Go to step 17.
2. NO - Repair open in the wire between the A/F sensor relay and the No. 9 LAFHT (15 A) fuse in the under-hood subfuse box. If the No. 9 LAFHT (15 A) fuse is blown, repair the cause, then go to step 12.
Install the A/F sensor relay, and reconnect PCM connector B (56P).
Turn the ignition switch ON (II).
Reset the PCM with the HDS.
Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?
1. YES - If DTC P0657 is indicated, check for poor connections or loose terminals at the A/F sensor relay and the PCM, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
2. NO - Troubleshooting is complete.
Test the A/F sensor relay (see POWER RELAY TEST ).
Is the relay OK?
1. YES - Go to step 22.
2. NO - Replace the A/F sensor relay, then go to step 18.
Turn the ignition switch ON (II).
Reset the PCM with the HDS.
Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?
1. YES - If DTC P0657 is indicated, check for poor connections or loose terminals at the A/F sensor relay and the PCM, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
2. NO - Troubleshooting is complete.
Update the PCM if it does not have the latest software, or substitute a known-good PCM (see PCM UPDATING AND SUBSTITUTION FOR TESTING ).
Turn the ignition switch ON (II).
Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?
1. YES - If DTC P0657 is indicated, check for poor connections or loose terminals at the A/F sensor relay and the PCM, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
2. NO - If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ).