CAT Engine 76 Fault Code: Cylinder #7 Injector : Current Above Normal
Also called Cylinder #7 Current Above Normal, Cylinder #7 Injector : Current Below Normal, Cylinder #7 Injector Short, Cylinder #7 Injector current above normal, Cylinder #7 Injector short, Cylinder #7 Injector:Current Above Normal, Cylinder 7 Shorted, Injector Cylinder 7 Short, Injector Cylinder 7 short
Cylinder #7 Injector : Current Above Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 76, SPN 7 / FMI 6, means the ECM has detected a short to ground or a short across the electrical load (an internal short) on the cylinder #7 injector solenoid circuit. The ECM disables that solenoid circuit to prevent damage and periodically retries firing it. Affects C15, C175, C27, and C32 engines with Electronic Unit Injectors.
High severity. The engine can keep running on the remaining cylinders, but cylinder #7 is misfiring or dead, and the ECM is repeatedly cutting out and retrying a shorted circuit. Left unaddressed, this causes rough running, power loss, and potential damage to the injector solenoid or wiring from continued high current attempts. Diagnose before continued heavy load operation.
What does CAT Engine error code 76 mean?
CAT engines with Electronic Unit Injectors (EUI) use injectors that are mechanically actuated but electronically controlled. Each injector has two solenoids, and the ECM sends a 105 volt pulse to each one at the correct time and duration for the current engine load and speed.
The ECM constantly monitors current flow through each solenoid circuit. Code 76 specifically means the ECM detected a short to ground or a short across the electrical load, essentially an internal short in the solenoid, on cylinder #7. When this happens, the ECM disables that solenoid circuit to protect it from damage caused by the high current flow, then periodically tries to fire the injector again. If the short is still present, this cycle repeats indefinitely until the problem is fixed.
This is different from the related open-circuit or short-to-battery-voltage condition, which causes low current and a different code behavior. Code 76 (FMI 6) is specifically the short-to-ground/internal-short condition, and it triggers an active disable-and-retry cycle rather than a simple continued firing attempt.
Common causes of 76
- Problem in the fuel system
- A cylinder is malfunctioning
- Damaged injector connectors
- Damaged engine wiring harness
- Failed injector solenoid (internal short)
- Failed valve cover base wire harness
- Improper injector adjustment and/or engine valve clearance
- Faulty harness between the ECM and the valve cover base, or under the valve cover itself
- Bad or corroded connectors or wiring
- Faulty ECM (less common, but listed as a possible cause)
- Intermittent wiring or connector problem that only shows up under engine vibration or heavy load
How to troubleshoot CAT Engine 76: first checks
- Run the engine to normal operating temperature before testing. Problems with injector solenoids typically show up once the engine is warmed up and/or under vibration from heavy loads, so a cold, no-load check can miss the fault.
- Inspect the cylinder #7 injector connector and surrounding wiring closely for corrosion, damage, or looseness. Pay careful attention to wiring and connector condition since these often only cause trouble during vibration.
- Check the wiring harness routing between the ECM and the valve cover base, and the harness underneath the valve cover, for chafing, pinched wires, or moisture intrusion.
- Use a diagnostic scan tool to confirm whether the code is active or logged, and watch for it re-triggering as the ECM periodically retries firing the injector.
- Verify injector adjustment and engine valve clearance are within spec, since improper adjustment is a listed possible cause.
- If wiring and connectors check out, test the injector solenoid itself for an internal short, and consider swapping or bench-testing the injector on cylinder #7.
- If the injector and harness both check out, the ECM itself is a possible (though less likely) cause and may need testing or replacement.
How the code clears
No separate clearing step is listed. The ECM will keep periodically retrying the solenoid circuit as long as the short is present, and the code will stay active on the scan tool or diagnostic lamp until the underlying wiring, connector, injector, or ECM problem is repaired. Once the fault is corrected, the ECM should stop cutting out the circuit and the code should clear on its own.
Affected models and serial ranges
76 appears in our records across 4 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C15 | Serial range not listed in source records |
| C175 | 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 76 mean?
It means the ECM detected a short to ground or an internal short across the electrical load on the cylinder #7 injector solenoid circuit (SPN 7, FMI 6). The ECM disables that circuit to prevent damage and keeps periodically retrying it until the short is fixed.
Can I keep running the engine with code 76 active?
The engine will typically keep running on the other cylinders, but cylinder #7 will misfire or not fire at all, causing rough running and power loss. Continuing to run under heavy load with an active short can risk further damage to the solenoid or wiring, so it should be diagnosed before extended operation.
What is the most common cause of an injector short code like this?
Damaged or corroded connectors and wiring are frequently cited causes, along with a failed injector solenoid itself. Wiring problems, especially ones that only show up under vibration or heavy load, are worth checking closely before assuming the injector or ECM is bad.
Why does this fault often only show up when the engine is warm or working hard?
Problems with injector solenoids and their wiring typically appear once the engine reaches normal operating temperature and/or is under vibration from heavy loads. That is why diagnostic checks should be performed with the engine warmed up rather than cold and idling.
Does code 76 mean I need a new injector?
Not necessarily. A bad injector solenoid is one possible cause, but damaged connectors, harness wiring, improper injector adjustment or valve clearance, and even a faulty ECM are all listed as possible causes. Wiring and connectors should be checked first since they are the more common and cheaper fix.
How does the ECM respond when this code is active?
The ECM disables the affected solenoid circuit to prevent damage from the high current caused by the short, then periodically attempts to fire the injector again. If the short is still present, this disable-and-retry cycle repeats indefinitely until the problem is corrected.
Is there a difference between code 76 and a similar open-circuit code?
Yes. Code 76 (FMI 6) covers a short to ground or short across the electrical load, an internal short. The open-circuit variant covers an open circuit or a short to battery voltage instead, which causes low current rather than high current, and the ECM's response differs accordingly.