CAT Engine 26126 Fault Code: Cylinder #6 Injector Actuator #2:Current Above Normal
Also called Cylinder #6 Injector Actuator #2 - Current Above Normal, Cylinder #6 Injector Actuator #2 : Current Above Normal
Cylinder #6 Injector Actuator #2:Current Above Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 26126 (SPN 3664, FMI 6) means the ECM detected high current flow on the #2 solenoid circuit of the Cylinder #6 injector. The ECM shuts that solenoid circuit down to prevent damage, then periodically retries firing it. Applies to C13, C15, C18, C27, and C32 engines.
High severity. A shorted injector solenoid circuit causes the ECM to disable that solenoid, which can lead to a misfire, rough running, or loss of power on cylinder #6. It will not usually strand the machine immediately, but leaving it unresolved risks harness or ECM damage and worsening performance. Diagnose before continued heavy-load operation.
What does CAT Engine error code 26126 mean?
This engine uses Electronic Unit Injectors, mechanically actuated and electronically controlled. Each injector has two solenoids, and the ECM fires each one with a 105 volt pulse at a precise time and duration matched to engine load and speed.
The ECM continuously monitors current flow through each solenoid circuit. Code 26126 sets when the ECM sees current above the normal range on the #2 solenoid of the Cylinder #6 injector, which the ECM interprets as a short circuit condition.
When this happens, the ECM disables that solenoid circuit to protect it from damage, but it does not give up. It periodically attempts to fire the injector again. If the short is still present, this disable-and-retry cycle repeats until the underlying wiring, connector, or component problem is fixed.
Common causes of 26126
- Damaged, corroded, or shorted connectors or wiring at the injector solenoid circuit
- A fault in the wiring harness between the ECM and the connector, or between the ECM and the valve cover base
- A fault in the harness under the valve cover
- An open or short in the wire feeding the #2 solenoid
- A faulty or failed injector solenoid, requiring injector replacement
- An intermittent connection issue that only shows up under vibration or heavy load
- A faulty ECM (less common, but listed as a possible cause if wiring and injector check out good)
How to troubleshoot CAT Engine 26126: first checks
- Bring the engine to normal operating temperature before testing since these faults often only appear once the engine is warmed up
- Inspect all connectors and wiring on the Cylinder #6 injector circuit for corrosion, damage, chafing, or loose pins
- Wiggle-test the harness and connectors while watching for the fault to reappear, since vibration under heavy load is a common trigger
- Check the harness between the ECM and the connector, and the harness between the ECM and the valve cover base, for continuity and no open circuits
- Inspect the harness routing under the valve cover for pinching, rubbing, or heat damage
- If wiring and connectors check out good, test the injector solenoid itself and be prepared to replace the injector
- Only after ruling out wiring, connectors, harness, and injector should the ECM be suspected as the cause
How the code clears
No separate clearing step is listed. Once the root cause (bad wiring, connector, harness, or injector) is repaired or replaced, the ECM should stop logging the fault on its own as it resumes normal current monitoring on that solenoid circuit. Confirm repair by clearing logged codes with diagnostic software and running the engine under load to verify the code does not return.
Affected models and serial ranges
26126 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 code 26126 mean?
It means the ECM detected current above the normal range on the #2 solenoid circuit for the Cylinder #6 fuel injector, which it treats as a short circuit and responds to by disabling that solenoid circuit.
Which CAT engines can throw code 26126?
This code applies to C13, C15, C18, C27, and C32 engines equipped with Electronic Unit Injectors.
Can I keep running the engine with this code active?
The ECM will keep trying to fire the injector periodically, but with the solenoid circuit disabled, expect a misfire or rough running on that cylinder. It is best to diagnose and repair the issue rather than run it continuously, since repeated short-circuit cycling can risk further wiring or ECM damage.
Why does this fault often show up only when the engine is warmed up or under load?
Wiring and connector problems, including corrosion and loose or chafed connections, often only cause a short or open circuit intermittently, especially under the vibration that comes with heavy load or once components have expanded from heat. This is why the diagnostic procedure calls for testing at normal operating temperature.
Is the injector itself always the problem?
Not necessarily. Wiring, connectors, and the harness between the ECM and the injector are the most commonly listed causes. The injector solenoid itself and, in rare cases, the ECM are also listed as possible causes if the wiring checks out fine.
Do I need to manually clear code 26126 after the repair?
No separate clearing step is listed for this code. Once the root cause is fixed, the ECM should stop setting the fault. Clearing the stored code with diagnostic software and running the engine under representative conditions confirms the repair held.
What is the risk if code 26126 is ignored?
Continued short-circuit cycling on the solenoid circuit can lead to further wiring or harness damage, degraded engine performance from the disabled cylinder, and in some cases contribute to ECM stress. It is treated as a repair-soon issue rather than an immediate shutdown.