CAT Engine 26086 Fault Code: Cylinder #4 Injector Actuator #2:Current Above Normal
Also called Cylinder #4 Injector Actuator #2 - Current Above Normal, Cylinder #4 Injector Actuator #2 : Current Above Normal
Cylinder #4 Injector Actuator #2:Current Above Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 26086 (SPN 3662 / FMI 6) means the ECM detected excessive current in the circuit for the #2 solenoid on the #4 cylinder's electronic unit injector. The ECM disables that solenoid circuit to prevent damage, then periodically retries firing it. This affects C13, C15, C18, C27, and C32 engines and points to wiring, connector, injector, or ECM problems.
High severity. The ECM shuts down the affected solenoid circuit to protect itself, which means cylinder #4 may misfire or run rough. Left unaddressed, repeated high-current events can damage the injector driver circuit in the ECM. Diagnose promptly rather than running the machine indefinitely with the fault active.
What does CAT Engine error code 26086 mean?
CAT engines in this family use Electronic Unit Injectors (EUI) that are mechanically actuated and electronically controlled. Each injector has two solenoids, and the ECM sends 105 volt pulses to each solenoid at a precise time and duration matched to engine load and speed.
The ECM constantly monitors current flow through each solenoid circuit. Fault code 26086 sets when the ECM detects current above normal levels on the #2 actuator solenoid for cylinder #4. To protect the driver circuitry from damage, the ECM disables that solenoid circuit once high current is detected, but it will periodically attempt to fire the injector again. If the short circuit condition is still present, this cycle of disable and retry repeats until the underlying problem is fixed.
Because this is a current-above-normal condition rather than an open circuit, the most likely culprits are a short somewhere in the wiring, a damaged connector, or a failing injector solenoid itself. Chasing this fault means checking the physical health of the circuit under conditions that match when the problem actually shows up.
Common causes of 26086
- Damaged, chafed, or shorted wiring or connectors between the ECM and the injector, including the harness that runs between the ECM and the connector, the valve cover base, or under the valve cover itself
- An intermittent connection issue that only appears once the engine is warmed up or under heavy load and vibration
- A faulty injector or failing injector solenoid on cylinder #4's #2 actuator
- An internal electronic problem with the injector itself
- A faulty ECM, including possible internal driver circuit failure
- An intermittent fault that is hard to reproduce at idle or cold, but appears reliably once the engine reaches normal operating temperature and is under load
How to troubleshoot CAT Engine 26086: first checks
- Run the engine to normal operating temperature before testing since these problems typically only show up once warm and/or under vibration from heavy load
- Inspect all connectors in the injector solenoid circuit for corrosion, looseness, pushed-back pins, or moisture intrusion, paying close attention because vibration-related faults may not show up with the engine stationary and cold
- Visually and physically inspect the wiring harness between the ECM and the injector connector, the valve cover base, and the harness routed under the valve cover, looking for chafing, pinched sections, or exposed conductors that could short
- Check the harness between the ECM and the connector for continuity to confirm there is no open circuit hiding alongside the short
- Wiggle-test the harness and connectors while monitoring for the fault to reappear, since intermittent shorts often only show up under vibration
- If wiring and connectors check out, test the injector solenoid itself and be prepared to swap or bench-test the injector
- Consider ECM involvement only after wiring, connectors, and injector have been ruled out, since ECM failure is listed as a possible but less common cause
How the code clears
No separate clearing step is listed beyond correcting the underlying wiring, connector, injector, or ECM problem. Once the short or high-current condition is repaired, the ECM should stop disabling the solenoid circuit and the code should not continue to log. There is no stated manual reset procedure independent of fixing the fault.
Affected models and serial ranges
26086 appears in our records across 5 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C13 | Serial range not listed in source records |
| C15 | Serial range not listed in source records |
| C18 | Serial range not listed in source records |
| C27 | Serial range not listed in source records |
| C32 | Serial range not listed in source records |
Frequently asked questions
What does CAT fault code 26086 mean?
It means the ECM detected current above normal in the circuit for the #2 actuator solenoid on the #4 cylinder's electronic unit injector. This is SPN 3662, FMI 6. The ECM disables that solenoid circuit to prevent damage and periodically retries firing it.
Which CAT engines can show code 26086?
This code applies to C13, C15, C18, C27, and C32 engines that use Electronic Unit Injectors with dual solenoids controlled by the ECM.
Can I keep running the machine with this code active?
It is not recommended. The ECM has already disabled the affected solenoid circuit to protect itself, which can cause a rough-running or misfiring cylinder. Continued high-current events risk further damage to the ECM's driver circuitry, so it should be diagnosed as soon as practical.
Why does this fault often only appear when the engine is warmed up or working hard?
Problems with injector solenoid wiring and connectors are often heat- and vibration-related, meaning a marginal connection or wire may only fail once the engine reaches normal operating temperature and is under heavy load. Testing should be done under those same conditions to catch the fault.
What parts are usually replaced to fix code 26086?
Depending on what testing finds, repairs can involve replacing damaged connectors or wiring, replacing a harness section between the ECM and the injector or under the valve cover, replacing the injector itself, or in less common cases replacing the ECM.
Is code 26086 an open circuit or a short circuit problem?
This specific fault is a current-above-normal condition, which points toward a short circuit rather than an open circuit. A separate low-current fault would indicate an open in the circuit instead.
Will this code clear itself after I fix the wiring or injector?
There is no separate reset procedure listed. Once the underlying wiring, connector, injector, or ECM issue is corrected, the ECM should stop seeing high current and stop logging the fault.