Injection Pump Fuel Metering Control Faults (10 codes)

What these codes mean

These ten entries distinguish control A and control B, with separate general fault, range/performance, low, high and intermittent descriptions. P0251/P0256 identify the general controls; P0252/P0257 are range/performance, P0253/P0258 low, P0254/P0259 high and P0255/P0260 intermittent. The member list preserves every complete code and its own page.

A and B identify controls assigned by the manufacturer. They do not establish a second physical pump, an engine bank or interchangeable components. The historical Cam/Rotor/Injector parenthetical is part of the description, not a list of failed parts. Actual applications can differ: GM’s 00064H worksheet uses P0251 for a pump cam-sensor circuit on its listed 6.5L diesel vehicles, while Jaguar’s 2019 SSM 74589 lists P0251-13 and P0256-13 on covered AJ126 gasoline applications. Identify the exact engine, reporting module and full DTC before selecting a test.

Low and high describe the monitored electrical/control characteristic. They are not direct fuel-pressure or delivered-quantity measurements. Driver design and commanded state determine what a connected, disconnected or loaded reading means. A changed reading after unplugging a component does not universally distinguish a pump from its wiring or controller. Never transplant a pin number, lamp response, resistance limit or voltage comparison from another control.

Range/performance requires the specified operating conditions and relationship between command and response. A normal static resistance does not complete that diagnosis or certify the rest of the circuit. Intermittent faults need their own event information and approved capture method; a successful restart or one normal workshop reading does not establish a repair. An A/B comparison is useful only where the manufacturer defines and permits it.

Save the complete scan, suffix, status and available event data. Tell the shop whether the complaint occurs during starting or running, cold or warm, and whether fuel, wiring or module work preceded it. Ask which measured result establishes the proposed repair. A wiring repair, a sensing/control component, a pump assembly and programming are different possible jobs. The member pages’ national diagnostic-labor example does not include those repairs.

Initial code and electrical assessment should keep the fuel system closed. Component isolation, pressure release, cleanliness, seals and setup depend on the actual system. Do not apply battery power to an unidentified control, disturb live fuel wiring, loosen a high-pressure line or provoke a stall to find a fault. Stop safely for leakage or strong fuel odor, stalling, severe rough running or unsafe power loss, and follow the vehicle’s warning instructions.