DTC P0251 [WL-3]

id0102b8830500

DTC P0251

Injection amount control system malfunction
DETECTION CONDITION
•  The PCM monitors the difference in voltage between the target injection amount and the actual injection amount while the engine is running. If the difference in voltage is above the threshold for 0.5 s, the PCM determines that the injection amount control system is malfunctioning.
POSSIBLE CAUSE
•  Connector or terminal malfunction
•  Open circuit in wiring harness between fuel injection pump connector A terminal I and main relay terminal D
•  Open circuit in wiring harness between fuel injection pump connector A terminal L and PCM terminal 4Y
•  Open or short to ground in wiring harness between fuel injection pump connector A terminal L and PCM terminal 4Y
•  Electronic governor malfunction
•  Fuel Injection pump (injection amount control) malfunction
•  PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION
1
VERIFY RELATED REPAIR INFORMATION AVAILABILITY
•  Verify related service repair information availability.
•  Is any related repair information available?
Yes
Perform repair or diagnosis according to the available repair information.
•  If the vehicle is not repaired, go to the next step.
No
Go to the next step.
2
VERIFY CURRENT SIGNAL STATUS: IS CONCERN INTERMITTENT OR CONSTANT?
•  Clear the DTC.
•  Start the engine.
•  Is the same DTC present?
Yes
Go to the next step.
No
Intermittent concern exists.
Perform the “INTERMITTENT CONCERN TROUBLESHOOTING”.
(See INTERMITTENT CONCERN TROUBLESHOOTING [WL-3].)
3
VERIFY IF OTHER DTCS ARE PRESENT
•  Are other DTCs present?
Yes
Perform the appropriate DTC troubleshooting procedure.
(See DTC TABLE [WL-3].)
then go to Step 8.
No
Go to the next step.
4
INSPECT FUEL INJECTION PUMP CONNECTOR FOR POOR CONNECTION
•  Turn the engine switch to the off position.
•  Disconnect the fuel injection pump connector A.
•  Check for poor connection (damaged, pulled-out pins, corrosion, etc.).
•  Is there a malfunction?
Yes
Repair or replace the terminal, then go to Step 9.
No
Go to the next step.
5
INSPECT ELECTRONIC GOVERNOR POWER CIRCUIT
•  Turn the engine switch to the ON position (Engine off).
•  Measure the voltage between fuel injection pump connector A terminal I (wiring harness-side) and body ground.
•  Is the voltage B+?
Yes
Go to the next step.
No
Repair or replace the electronic governor power circuit for an open circuit, then go to Step 9.
6
INSPECT ELECTRONIC GOVERNOR CONTROL CIRCUIT FOR SHORT TO GROUND
•  Turn the engine switch to the off position.
•  Check for continuity between fuel injection pump connector A terminal L (wiring harness-side) and body ground.
•  Is there continuity?
Yes
Repair or replace electronic governor control circuit for an short to ground, then go to Step 9.
No
Go to the next step.
7
INSPECT PCM CONNECTOR FOR POOR CONNECTION
•  Disconnect the PCM connector.
•  Check for poor connection (damaged, pulled-out pins, corrosion, etc.).
•  Is there a malfunction?
Yes
Repair or replace the terminal, then go to Step 9.
No
Go to the next step.
8
INSPECT ELECTRONIC GOVERNOR CONTROL CIRCUIT FOR OPEN CIRCUIT
•  Check for continuity between fuel injection pump connector A terminal L (wiring harness-side) and PCM terminal 4Y (wiring harness-side).
•  Is there continuity?
Yes
Fuel injection pump may have malfunction. Consult your distributor for inspection of fuel injection pump.
Go to the next step.
No
Repair or replace the electronic governor control circuit for an open circuit, then go to the next step.
9
INSPECT ELECTRONIC GOVERNOR
•  Perform the electronic governor Inspection.
•  Is the electronic governor normal?
Yes
The fuel injection pump may have the mechanical malfunction. Consult your distributor for the inspection of the fuel injection pump.
Then go to the next step.
No
Consult your distributor for the replacement of the electronic governor.
Then go to the next step.
10
VERIFY TROUBLESHOOTING OF DTC P0251 COMPLETED
•  Make sure to reconnect all disconnected connectors.
•  Turn the engine switch to the ON position (Engine off).
•  Clear the DTCs from the PCM memory using the M-MDS.
•  Start the engine.
•  Is the same DTC present?
Yes
Replace the PCM, then go to the next step.
No
Go to the next step.
11
VERIFY AFTER REPAIR PROCEDURE
•  Perform “AFTER REPAIR PROCEDURE”.
•  Is there any DTC present?
Yes
Go to applicable DTC inspection.
(See DTC TABLE [WL-3].)
No
Troubleshooting completed.