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28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM)/Diagnosis and Testing
P0251-CP3 PUMP REGULATOR CONTROL
For a complete wiring diagram Refer to the Wiring Information.
When Monitored:
When the ignition is on.
Set Condition:
The ECM detects a discrepancy between the PWM supplied to the Electronic Fuel Control Actuator and the PWM returned from the Electronic Fuel Control Actuator.
Possible Causes
FUEL PUMP
(K604) FUEL CONTROL ACTUATOR DRIVER OPEN
(K65) RETURN CIRCUIT OPEN FROM FCA TO ECM
(K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGE
(K65) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO EXTERNAL VOLTAGE
(K65) FCA RETURN CIRCUIT SHORTED TO (K604) FCA DRIVER CIRCUIT
(K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO GROUND
(K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO ANOTHER CIRCUIT
(K65) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO ANOTHER CIRCUIT
INTERMITTENT CONDITION
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
1.FUEL PUMP
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1. Ignition on, engine not running.
2. Disconnect the Fuel Control Actuator (FCA) harness connector.
3. Connect an incandescent test light across the Fuel Control Actuator driver circuit and the Fuel Control Actuator return circuit at the fuel control actuator harness connector.
4. Observe the test light.
5. The ECM will perform a self test of the circuit which should momentarily flash the test light brightly, one time, approximately 20 seconds after being connected.
NOTE: Check connectors - Clean/repair as necessary.
NOTE: Compare test light brightness to that of a direct connection to the battery.
Did the light flash brightly?
Yes
Replace the Fuel Pump.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
No
Go To 2
2.(K604) FUEL CONTROL ACTUATOR DRIVER OPEN
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1. Turn the ignition off.
2. Disconnect the ECM harness connectors.
NOTE: Check connectors - Clean/repair as necessary.
3. Measure the resistance of the FCA driver circuit between the electronic fuel control actuator harness connector and the ECM harness connector.
Is the resistance less than 10 Ohms?
Yes
Go To 3
No
Repair the (K604) Fuel Control Actuator Driver circuit OPEN.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
3.(K65) RETURN CIRCUIT OPEN
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1. Measure the resistance of the (K65) return circuit between the FCA harness connector and the ECM harness connector.
Is the resistance less than 10 Ohms?
Yes
Go To 4
No
Repair or replace the engine wiring harness.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
4.(K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGE
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1. Measure the voltage between the (K604) FCA driver circuit in the FCA harness connector and battery negative.
Is the voltage greater than 1 volts?
Yes
Repair the (K604) FCA driver circuit shorted to external voltage.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
No
Go To 5
5.(K65) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO EXTERNAL VOLTAGE
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1. Measure the voltage between the (K65) FCA return circuit in the FCA harness connector and battery negative.
Is the voltage greater than 1 volts?
Yes
Repair the (K65) FCA return circuit shorted to external voltage.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
No
Go To 6
6.(K65) FCA RETURN CIRCUIT SHORTED TO (K604) FCA DRIVER CIRCUIT
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1. Measure the Resistance between the return circuit in the FCA harness connector and Driver circuit.
Is the resistance less than 10 Ohms?
Yes
Repair the (K65) FCA Return circuit shorted to (K604) FCA Driver circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
No
Go To 7
7.(K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO GROUND
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1. Measure the resistance between the (K604) FCA driver circuit in the FCA harness connector and battery negative.
Is the resistance less than 10 Ohms?
Yes
Repair the (K604) FCA driver circuit shorted to ground.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
No
Go To 8
8.(K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO ANOTHER CIRCUIT
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1. Measure the resistance between the (K604) FCA driver circuit in the ECM harness connector and all other circuits in the ECM connectors.
Is the resistance less than 10 Ohms?
No
Go To 9
Yes
Repair the (K604) FCA driver circuit shorted to another circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
9.(K65) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO ANOTHER CIRCUIT
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1. Measure the resistance between the (K65) FCA Return circuit in the ECM harness connector and all other circuits in the ECM connectors.`
Is the resistance less than 10 Ohms?
No
Go To 10
Yes
Repair the (K65) FCA Return circuit shorted to another circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
10.ECM
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1. Reconnect the ECM harness connectors.
2. Ignition on, engine not running.
3. Disconnect the Electronic Fuel Control Actuator connector.
4. Connect an incandescent test light across the Fuel Control Actuator driver pin and the Fuel Control Actuator return wire at the fuel control actuator connector.
5. Observe the test light.
6. The ECM will perform a self test of the circuit which should momentarily flash the test light brightly, one time, approximately 20 seconds after being connected.
NOTE: Compare test light brightness to that of a direct connection to the battery.
Did the light flash brightly?
Yes
Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
No
Replace the ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)
__________________
Travis
My rig - 2021 Mega 3500 SRW
My Classic - 79 Chevy Silverado
Quote:
Originally Posted by RonA
Trucks are like women. Sometimes you just need to spend money on them to keep them happy.
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