P2624 indicates that the engine control module has detected a low-voltage condition in the injector control pressure regulator (IPR) circuit. The IPR valve regulates high-pressure oil that actuates the fuel injectors, so a circuit fault can disrupt injection timing and fuel delivery. This code is most commonly seen on diesel engines that use a high-pressure oil system, such as certain Ford Power Stroke applications.
The injection pressure regulator valve itself can fail internally with an open coil or short to ground, pulling the circuit voltage low. This is the most common cause of P2624.
Chafed or damaged wiring between the IPR valve and the PCM can short the control circuit to ground, causing the low-voltage reading. Heat and vibration near the engine make this a frequent failure point.
Corrosion, bent pins, or a pushed-back terminal at the IPR connector can create high resistance or an intermittent connection that the PCM interprets as a circuit fault.
A broken wire or disconnected terminal in the IPR control circuit can prevent current flow, resulting in a low-voltage signal at the PCM.
The internal driver in the PCM that controls the IPR valve can fail, though this is rare. This should only be considered after all wiring, connectors, and the IPR valve itself have been verified good.
It is not recommended. The engine may stall, fail to restart, or run poorly enough to be unsafe in traffic. Have it diagnosed before driving any significant distance.
Almost never. The PCM driver is the least likely cause. In the vast majority of cases the IPR valve itself or the wiring/connector between the valve and the PCM is the problem. Replacing the PCM without ruling out the IPR and wiring first is a common and costly mistake.
Basic resistance testing across the IPR coil terminals is possible with a multimeter and published specifications. However, pinpointing intermittent wiring faults or confirming PCM output often requires a scan tool with bidirectional control and wiring diagrams, so professional diagnosis is advisable if basic checks are inconclusive.
The injection pressure regulator valve controls the amount of high-pressure oil sent to the injectors on certain diesel engines. By regulating that oil pressure, it directly affects injection timing and fuel quantity. If the IPR circuit fails, the PCM cannot properly control injector operation.