CAT Engine 106 Fault Code: Cylinder #10 Injector : Current Above Normal
Also called Cylinder #10 Injector Current Above Normal, Cylinder #10 Injector Short, Cylinder #10 Injector current above normal, Cylinder #10 Injector short, Cylinder #10 Injector:Current Above Normal, Injector Cylinder 10 Short, Injector Cylinder 10 short
Cylinder #10 Injector : Current Above Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 106 (SPN 10 / FMI 6) means the ECM detected a short circuit in the #10 cylinder injector solenoid on C15, C175, C27, or C32 engines. The ECM disables that solenoid circuit to prevent damage, then keeps trying to fire the injector periodically. The engine will keep running but that cylinder will misfire or drop out until the short is repaired.
High severity. The engine can keep running, but one injector is effectively disabled and will periodically be re-tried by the ECM, which can cause rough running, power loss, and repeated cycling of the fault. Left unaddressed, wiring or solenoid damage can worsen, and other injectors on the same harness path may be affected. Diagnose before continued heavy-load operation.
What does CAT Engine error code 106 mean?
CAT C15, C175, C27, and C32 engines 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 the correct time and duration for the current engine load and speed.
The ECM continuously monitors current flow through each solenoid circuit. Low current flow triggers a different diagnostic code, but the ECM keeps trying to fire that injector. High current flow (a short) triggers code 106. When this happens, the ECM disables the solenoid circuit to prevent damage from the excess current, then periodically attempts to fire the injector again. If the short is still present, this disable-and-retry cycle repeats until the underlying problem is fixed.
In plain terms: the ECM thinks cylinder #10's injector solenoid circuit is shorted, so it is protecting itself by cutting power to that circuit rather than letting it draw dangerous current, while still checking periodically to see if the short has cleared.
Common causes of 106
- Electronic problem with the injector solenoid itself (bad injector or bad injector solenoid)
- Damaged, corroded, or bad connectors and/or wiring in the injector circuit
- Problem in the harness, including the harness between the ECM and the valve cover base, or the harness under the valve cover
- Intermittent problem that only shows up under vibration or heavy load once the engine is warmed up
- Faulty ECM
How to troubleshoot CAT Engine 106: first checks
- Run the engine to normal operating temperature first, since injector solenoid problems typically show up once warmed up and under vibration or heavy load; check while it is at operating temperature rather than cold.
- Inspect all connectors and wiring in the #10 injector circuit for corrosion, looseness, chafing, or damage, paying close attention because problems can be intermittent and only appear under vibration.
- Trace the harness between the ECM and the valve cover base and the harness under the valve cover for pinches, chafe points, or breaks.
- Wiggle-test the harness and connectors while monitoring for the fault, since vibration-related faults may not show up with the engine sitting still.
- If wiring and connectors check out, test the injector solenoid itself, and if that checks out, suspect the ECM as a last resort.
How the code clears
No separate clearing step is listed beyond fixing the underlying short. The ECM logs the code and disables the affected solenoid circuit, then periodically retries firing the injector on its own. Once the short circuit is repaired (wiring, connector, injector, or ECM as needed), the ECM's normal retry cycle should pick up the injector again without a manual reset procedure being specified.
Affected models and serial ranges
106 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 fault code 106 mean?
It means the ECM detected a short circuit (high current flow) in the #10 cylinder injector solenoid circuit on a C15, C175, C27, or C32 engine. This is SPN 10, FMI 6. The ECM disables that solenoid circuit and periodically retries firing it until the short is fixed.
Can I keep running the engine with code 106 active?
The engine will generally keep running, but cylinder #10 will be misfiring or not firing consistently since its solenoid circuit is disabled and only retried periodically. Extended operation under load with a disabled injector circuit is not good practice, so it should be diagnosed and repaired promptly.
Why does this fault often show up only when the engine is warmed up?
Injector solenoid problems typically occur once the engine reaches normal operating temperature and/or when the engine is under vibration from heavy loads. Wiring and connector issues especially can be intermittent and only appear under those conditions, which is why diagnostics should be performed at normal operating temperature.
What voltage does the ECM send to the injector solenoids?
The ECM sends 105 volt pulses to each injector solenoid, timed and durated for the current engine load and speed.
Is code 106 caused by the injector or by wiring?
It can be either. Listed causes include damaged connectors or wiring, harness problems (including the harness between the ECM and valve cover base, or under the valve cover), a faulty injector solenoid, or in some cases a faulty ECM. Wiring and connectors should be checked first since they are the most common and least expensive fix.
Does code 106 require an ECM replacement?
Not usually. ECM replacement is listed as a possible cause but is generally the last thing to suspect after wiring, connectors, harness, and the injector itself have been checked and ruled out.
Is there a difference between low current and high current injector faults?
Yes. Low current flow in the solenoid circuit triggers a different diagnostic code and the ECM keeps trying to fire the injector normally. High current flow (a short) is what triggers code 106, and the ECM responds by disabling that solenoid circuit to prevent damage.