What Does P0257 Mean?
The ECM has detected a general malfunction in the injection pump fuel metering control 'B' circuit associated with the cam, rotor, or injector mechanism. This code indicates the secondary fuel metering control on a diesel injection pump is not functioning within expected parameters. The 'B' designation typically refers to a second metering control valve or a different operating range of the injection pump.
Common Causes
35%
Failed fuel metering control solenoid 'B' with internal short or open circuit
30%
Wiring harness fault between ECM and injection pump metering solenoid B
20%
Injection pump internal mechanical failure affecting fuel metering
15%
ECM output driver failure for metering control B circuit
Diagnostic Steps
1
Step 1: Identify the fuel metering control solenoid 'B' on the injection pump using manufacturer service data — measure solenoid resistance (typically 2-8 ohms) and compare to specification.
2
Step 2: Backprobe the solenoid connector and verify ECM command signal using an oscilloscope — look for proper PWM duty cycle pattern during cranking and idle.
3
Step 3: Check wiring continuity and insulation from the ECM connector to the metering solenoid connector — resistance should be less than 1 ohm with no shorts to ground or power.
4
Step 4: Command the metering solenoid actuator test through bidirectional scan tool control — listen and feel for solenoid click and verify fuel delivery changes.
5
Step 5: If electrical tests pass, inspect injection pump for internal mechanical wear or debris in the metering valve by checking fuel pressure regulation with a diesel fuel pressure gauge.
Estimated Repair Cost
$250 - $1,500
Parts + labor, varies by vehicle and location
The ECM has detected a general malfunction in the injection pump fuel metering control 'B' circuit associated with the cam, rotor, or injector mechanism. This code indicates the secondary fuel metering control on a diesel injection pump is not functioning within expected parameters. The 'B' designat...
The most common cause of P0257 (Injection Pump Fuel Metering Control "B" Malfunction (Cam/Rotor/Injector)) is: Failed fuel metering control solenoid 'B' with internal short or open circuit
Typical repair costs for P0257 range from $250 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may run rough, have reduced power, or fail to start reliably. Drivable with caution but schedule repair promptly to avoid further injection pump damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0257 to identify the root cause.
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Quick Info
Category
Powertrain
System
Diesel Fuel Injection System
Difficulty
Type
Generic (SAE)
Recommended Tools
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