CAT Engine 425 Fault Code: Injector Actuation Valve Open Circuit
Also called Inejctor Actuation Valve Open Circuit, Injector Actuation Valve : Current Below Normal, Injector Actuation Valve Current Below Normal, Injector Actuation Valve current below normal, Injector Actuation Valve open circuit
Injector Actuation Valve Open Circuit · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 425 (SPN 42 / FMI 5) means the ECM has detected an open circuit or below-normal current in the injection actuation pressure control valve (IAPCV) circuit on C15 or C27 engines. This can cause misfires, low power, reduced rpm, or an engine shutdown. It is logged as soon as the ECM sees the fault while the engine is running, not cranking.
High severity. The IAPCV controls the high pressure oil that actuates the unit injectors. An open circuit here can cause misfires, power loss, rpm reduction, or a full engine shutdown, so this code should be diagnosed promptly rather than run through a shift.
What does CAT Engine error code 425 mean?
Fault code 425 points to the injection actuation pressure control valve (IAPCV) circuit, which lives inside the unit injector hydraulic pump on C15 and C27 engines. The IAPCV is a precision actuator that varies the pump's outlet flow based on a control current sent by the ECM, so that the pump only pressurizes as much high pressure oil as the engine actually needs at that moment.
The ECM constantly compares a desired actuation pressure from its internal performance maps to the actual pressure it is getting, and adjusts the control current up or down to correct any difference. Code 425 sets when the ECM sees current below the minimum threshold or an open circuit in that control loop, meaning the valve is not responding the way it should.
Because the IAPCV directly affects how injectors fire, a fault here can cause misfiring, reduced engine speed, low power, or a shutdown. The ECM will log the event and trigger a snapshot for later review with a scan tool.
What triggers a CAT Engine 425 code?
The ECM sets this code when it reads an open circuit to the IAPCV while desired current is greater than 0.2 Amps, the ECM has been powered for at least three seconds, battery voltage is greater than 9.0 VDC for two seconds, and the engine is not cranking. Once triggered, current to the IAPCV defaults to 0.0 Amps after 150 milliseconds, and the ECM attempts to re-communicate with the IAPCV at intervals of 120 milliseconds.
Common causes of 425
- Damaged, corroded, or abraded connectors and wiring, including pinch points in the harness
- A general problem with the wiring harness itself
- The IAPCV solenoid's resistance out of specification, which may mean the unit injector hydraulic pump needs replacement
- A faulty or failing IAPCV itself
- An intermittent electrical problem in the circuit
- A mechanical problem within the high pressure oil system, including a faulty unit injector hydraulic pump
- A problem with the ECM
How to troubleshoot CAT Engine 425: first checks
- Inspect the IAPCV connector and related harness connectors for corrosion, damage, loose pins, or moisture intrusion
- Trace the harness for abrasion, pinch points, or chafing, especially near routing points close to the engine block or pump
- Check battery voltage and confirm it stays above the ECM's power-up threshold; low or unstable voltage can affect diagnostics
- Use a scan tool to pull the logged snapshot data and confirm whether the fault is active or intermittent
- Measure the IAPCV solenoid's resistance against specification if you have the capability, since an out-of-spec reading points toward the valve or pump
- If wiring and connectors check out, consider the unit injector hydraulic pump and ECM as the next likely suspects
How the code clears
No separate clearing step is listed for this code. Once the underlying wiring, connector, IAPCV, pump, or ECM issue is repaired and the ECM no longer sees the open circuit or low current condition, the fault should stop logging on its own. Use a scan tool to confirm the code is no longer active after repairs.
Affected models and serial ranges
425 appears in our records across 2 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C15 | Serial range not listed in source records |
| C27 | Serial range not listed in source records |
Frequently asked questions
What does CAT fault code 425 mean?
It means the ECM detected an open circuit or a current below the minimum threshold in the injection actuation pressure control valve (IAPCV) circuit, which is part of the unit injector hydraulic pump on C15 and C27 engines.
Can I keep driving or running the machine with code 425 active?
It is risky. The engine may misfire, lose power, drop rpm, or shut down while this fault is active, so it should be diagnosed as soon as practical rather than ignored.
What is the IAPCV and why does it matter?
The IAPCV is a precision displacement control actuator inside the unit injector hydraulic pump. It adjusts pump outlet flow based on a control current from the ECM so the engine gets the correct high pressure oil for injector actuation at every operating condition.
What usually causes code 425?
Common causes include damaged or corroded connectors and wiring, harness problems like pinch points or abrasion, a faulty IAPCV, an out-of-spec solenoid resistance, a mechanical problem in the high pressure oil system, or in some cases a faulty ECM.
Does code 425 always mean the pump needs to be replaced?
Not always. Wiring and connector problems are common and cheaper to fix. But if the solenoid resistance is out of specification or the IAPCV itself is faulty, the unit injector hydraulic pump may need replacement.
How does the ECM respond once it detects this fault?
The ECM logs the code, triggers a snapshot, and defaults IAPCV current to 0.0 Amps after 150 milliseconds, then tries to re-communicate with the valve every 120 milliseconds while the fault persists.
Is there a specific reset procedure for code 425?
No reset procedure is listed for this code. Once the wiring, IAPCV, pump, or ECM issue causing the fault is repaired, the code should stop setting on its own.