DTC P2251

DTC P2251  : A/F Sensor (Sensor 1) VS Circuit High Voltage

DTC (PGM-FI)

1. Problem verification

   -1. Turn the vehicle to the ON mode.

   -2. Clear the DTC with the HDS.

   -3. Turn the vehicle to the OFF (LOCK) mode.

   -4. Enter the maintenance mode, then start the engine .

   -5. Hold the engine speed at 3000 RPM without load (in P or N) until the radiator fan comes on, then let it idle.

   -6. Check for Pending or Confirmed DTCs with the HDS.

   DTC Description	Confirmed DTC	Pending DTC
   P2251 A/F Sensor (Sensor 1) VS Circuit High Voltage

   DTC (PGM-FI)

   Is DTC P2251 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. If the on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the on-board snapshot .

2. Open wire check (VS line)

   -1. Turn the vehicle to the OFF (LOCK) mode.

   -2. Jump the SCS line with the HDS, and wait more than 1 minute.

   -3. Disconnect the following connectors.

   PCM connector E (80P)

   A/F sensor (Sensor 1) 6P connector

   -4. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	PCM connector E (80P): disconnected
   	A/F sensor (Sensor 1) 6P connector: disconnected
   Test point 1	A/F sensor (Sensor 1) 6P connector (female terminals) No. 6:
   Test point 2	PCM connector E (80P) No. 73

   Courtesy of HONDA, U.S.A., INC.

   Is there continuity?

   YES 

   Go to step 3.

   NO 

   Repair an open in the VS wire between the PCM (E73) and the A/F sensor (Sensor 1).

3. PCM internal circuit check

   -1. Reconnect the following connector.

   PCM connector E (80P)

   -2. Exit the SCS mode with the HDS.

   -3. Enter the maintenance mode, then start the engine .

   -4. Hold the engine speed at 3000 RPM without load (in P or N) until the radiator fan comes on, then let it idle.

   -5. Measure the voltage between test points 1 and 2.

   Test condition	Engine running
   	A/F sensor (Sensor 1) 6P connector: disconnected
   Test point 1	A/F sensor (Sensor 1) 6P connector (female terminals) No. 6:
   Test point 2	Body ground

   Courtesy of HONDA, U.S.A., INC.

   Is there about 0.2 V or less?

   YES 

   Check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM , then recheck. If DTC P2251 goes away and the PCM was substituted, replace the original PCM .

   NO 

   The PCM internal circuit is OK. Replace the A/F sensor (Sensor 1) .