CAT Engine 115 Fault Code: Cylinder #11 Injector : Current Below Normal
Also called Cylinder #11 Injector : Current Above Normal, Cylinder #11 Injector Current Below Normal, Cylinder #11 Injector Open Circuit, Cylinder #11 Injector current below normal, Cylinder #11 Injector open circuit, Cylinder #11 Injector:Current Below Normal, Injector Cylinder 11 Open Circuit, Injector Cylinder 11 open circuit
Cylinder #11 Injector : Current Below Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 115 (SPN 11 / FMI 5) means the ECM detected low current or an open circuit in the cylinder #11 injector solenoid circuit on C15, C175, C27, and C32 engines. The ECM keeps trying to fire the injector while the code is active, but this can mean a misfiring or dead cylinder, rough running, and lost power until the wiring, connector, injector, or ECM issue is fixed.
Medium severity. The ECM keeps attempting to fire the injector, so the engine typically keeps running, but a dead or misfiring cylinder causes rough operation, power loss, and possible long-term damage to related components if left unaddressed. Diagnose within the shift rather than continuing to run it hard.
What does CAT Engine error code 115 mean?
CAT code 115 applies to the cylinder #11 injector solenoid circuit on C15, C175, C27, and C32 engines equipped with Electronic Unit Injectors (EUI). These injectors are mechanically actuated and electronically controlled, and each one contains two solenoids. The ECM sends 105 volt pulses to each solenoid at the correct timing and duration for the current engine load and speed.
This code sets when the ECM detects either low current flow or an open circuit in the solenoid circuit. When low current or an open circuit is detected, the ECM logs the code but keeps trying to fire that injector. This is different from a high-current short condition, where the ECM disables the solenoid circuit to prevent damage and only periodically retries firing it.
Because the ECM keeps attempting to fire the injector when this specific open circuit/low current fault is active, the engine usually keeps running, but cylinder #11 may be misfiring, running weak, or not firing at all, which shows up as rough idle, vibration, and reduced power.
Common causes of 115
- Electrical problem within the injector solenoid itself (bad connectors, wiring, or an internal fault)
- Damaged or corroded connectors and wiring in the injector circuit
- Problem in the wiring harness, including the section between the ECM and the valve cover base, or the harness under the valve cover
- An opening (break) in a wire in the circuit
- Faulty or worn-out injector needing replacement
- Intermittent problem that only shows up under vibration or heavy load
- Faulty ECM
How to troubleshoot CAT Engine 115: first checks
- Run the engine to normal operating temperature before testing, since injector solenoid problems typically show up once the engine is warmed up and/or under vibration from heavy loads
- With the engine off and cool enough to work on safely, inspect all connectors and wiring for cylinder #11's injector circuit for corrosion, looseness, chafing, or damage
- Trace the harness between the ECM and the valve cover base, and the harness under the valve cover, looking for chafed, pinched, or broken wires
- Wiggle-test the harness and connectors while monitoring for the code, since intermittent faults often only appear under vibration
- Check the injector solenoid itself for continuity and proper resistance if wiring and connectors check out
- If wiring, connectors, and the injector all test good, suspect the ECM
How the code clears
No separate clearing step is listed for this code. Once the underlying wiring, connector, injector, or ECM issue is repaired and the ECM no longer detects low current or an open circuit on the cylinder #11 injector solenoid circuit, the code should stop being active. Confirm the repair by running the engine at normal operating temperature and under load, since these faults often only appear under those conditions.
Affected models and serial ranges
115 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 115 mean?
It means the ECM detected either low current flow or an open circuit in the cylinder #11 injector solenoid circuit. Each Electronic Unit Injector has two solenoids that receive 105 volt pulses from the ECM, and the ECM constantly monitors current flow through each one.
Can I keep running the engine with code 115 active?
The ECM keeps trying to fire the injector when this open circuit/low current fault is active, so the engine will usually keep running, but cylinder #11 may be misfiring or not firing at all. Expect rough running, vibration, and power loss. It's best to diagnose and repair it rather than running it hard indefinitely.
What usually causes this code?
Most cases trace back to damaged, corroded, or loose connectors and wiring, a problem somewhere in the harness (including between the ECM and valve cover base, or under the valve cover), a broken wire, or a worn-out injector. In some cases the ECM itself is faulty.
Why does this fault only show up sometimes?
Injector solenoid problems typically appear once the engine is warmed up and/or under vibration from heavy loads. Wiring and connectors can have issues that only surface under vibration, which is why intermittent faults are common with this code.
Is this the same as an injector short circuit code?
No. A short circuit (high current) triggers a different response where the ECM disables the solenoid circuit and only periodically retries firing it. Code 115 as covered here is the low current/open circuit condition, where the ECM keeps trying to fire the injector continuously.
Where should I start looking first?
Start with the connectors and wiring for the cylinder #11 injector circuit, since damaged or corroded wiring and connectors are the most commonly listed cause. Check the harness sections near the ECM and under the valve cover, then move to the injector and ECM if wiring checks out clean.
Will replacing the injector fix code 115?
It might, since a faulty injector or injector solenoid is a listed cause, but replacing the injector without first checking wiring and connectors risks missing the actual problem and wasting a part. Confirm the wiring and harness are good before condemning the injector.