CAT 26 Fault Code: Engine Injector Cylinder #02 : Current Above Normal
Engine Injector Cylinder #02 : Current Above Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 26, SPN 652 FMI 6, means the ECM detected high current flow (a short circuit) in the injector solenoid circuit for cylinder #02 on C13 and C15 engines. The ECM disables that solenoid circuit to prevent damage but keeps periodically retrying to fire the injector.
High severity. The ECM shuts down the affected injector circuit to protect itself, which can cause a rough-running or misfiring engine and reduced power. It is not an immediate stop-the-engine emergency, but it should be diagnosed promptly since the cylinder is effectively running degraded and repeated short-circuit cycling can cause further electrical damage.
What does CAT error code 26 mean?
This code points to cylinder #02's Electronic Unit Injector (EUI) solenoid circuit. The ECM sends 105 V pulses to each injector solenoid, timed and sized for the engine's current load and speed. It also monitors current flow through each solenoid circuit.
If the ECM sees low current flow, it flags an open circuit fault and keeps trying to fire the injector anyway. If it sees high current flow, that indicates a short circuit, and the ECM disables that solenoid circuit to prevent damage. It will periodically attempt to fire the injector again, so if the short is still present, this disable-and-retry cycle repeats.
In practice this means cylinder #02 may misfire, run rough, or lose power intermittently, especially since these problems often show up once the engine is warmed up or under vibration from heavy loads.
Common causes of 26
- Failed injector (the solenoid or internal wiring inside the injector itself has shorted)
- Wiring between the ECM and the valve cover has chafed, shorted, or degraded
- Wiring under the valve cover for the injector harness has failed or shorted
- Plugged oil outlet port on the exhaust valve rocker arm
How to troubleshoot CAT 26: first checks
- Bring the engine to normal operating temperature before testing, since injector solenoid problems typically show up once warmed up and under vibration from heavy loads
- Carefully inspect all wiring and connectors between the ECM and the valve cover, and under the valve cover for the injector harness, looking for chafing, corrosion, or damage that may only appear under vibration
- Check the oil outlet port on the exhaust valve rocker arm for cylinder #02 to confirm it is not plugged
- Test the injector solenoid circuit current draw for cylinder #02 to confirm whether the short circuit condition is present
- Inspect the injector itself for internal failure if wiring and the rocker arm oil port check out normal
How the code clears
No separate clearing step is listed. Repair the failed component, whether that is the injector, the ECM-to-valve-cover wiring, the under-valve-cover injector harness wiring, or the plugged rocker arm oil outlet port, and the ECM should stop detecting the high current condition. Because the ECM retries the injector periodically, the code should clear on its own once the short circuit is resolved and confirmed with a test run.
Affected models and serial ranges
26 appears in our records across 2 CAT 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 |
Frequently asked questions
What does CAT fault code 26 mean?
It means the ECM detected high current flow, a short circuit, in the injector solenoid circuit for cylinder #02 on a C13 or C15 engine. The ECM disables that circuit to protect itself and periodically retries firing the injector.
Is it safe to keep driving or running the engine with code 26 active?
The engine will typically keep running, but cylinder #02 may misfire or lose power since its injector circuit is disabled and only periodically retried. It's best to get it diagnosed soon rather than run it long term in this condition.
Why does this fault often show up only when the engine is warm or working hard?
Problems with an injector solenoid, and the wiring feeding it, typically appear once the engine reaches normal operating temperature and/or when it's under vibration from heavy loads. That's also why diagnosis should be performed with the engine warmed up.
What parts should a technician check first for code 26?
Start with the injector itself, then the wiring between the ECM and the valve cover, the wiring under the valve cover for the injector harness, and the oil outlet port on the exhaust valve rocker arm to make sure it isn't plugged.
Can a plugged rocker arm oil port really cause an electrical fault code like this?
Yes, on these engines a plugged oil outlet port on the exhaust valve rocker arm is listed as one of the possible causes of this specific injector current fault, alongside wiring and injector failures.
Will fault code 26 clear itself after repair?
No separate clearing step is listed. Once the short circuit is repaired, whether it was the injector, wiring, or the rocker arm oil port, the ECM should stop detecting the high current condition and the code should not recur.