CAT Engine 46 Fault Code: Cylinder #4 Injector : Current Above Normal
Also called Cylinder #4 Injector - Current Above Normal, Cylinder #4 Injector Current Above Normal, Cylinder #4 Injector current above normal, Cylinder #4 Injector: Current Above Normal, Engine Injector Cylinder #04 : Current Above Normal
Cylinder #4 Injector : Current Above Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 46, SPN 654 FMI 6, means the ECM has detected a short circuit (high current) in the solenoid or wiring for the No. 4 cylinder electronic unit injector on C13, C15, or C18 engines. The engine will run rough and lose power, and the ECM will keep trying to fire the injector while the fault remains.
Medium severity. The engine keeps running but with low power and rough running on one cylinder. It will not cause immediate catastrophic damage, but the ECM disables that injector circuit during the fault, so performance loss and repeated attempts to fire the injector make this worth diagnosing before the shift is done rather than ignoring it.
What does CAT Engine error code 46 mean?
This code applies to CAT C13, C15, and C18 engines equipped with Electronic Unit Injectors (EUI). Each injector has a solenoid mounted on top of the injector body, and the ECM sends timed voltage pulses, described as 105 volt pulses, to fire each solenoid at the correct time and duration for the current engine load and speed.
Code 46 fires specifically when the ECM sees a high current (short circuit) condition on the No. 4 cylinder injector circuit. This is different from a low current or open circuit fault. When the ECM detects the short, it disables that solenoid circuit to prevent damage from the excess current, but it will keep periodically attempting to fire the injector until the fault clears.
Because the ECM shares some internal wiring between injectors, a short in common wiring inside the ECM can also knock out other injectors that share that circuit; on four cylinder engines this can affect two injectors together, and on six cylinder engines it can affect three injectors together.
What triggers a CAT Engine 46 code?
The ECM logs this code when it sees a high current (short circuit) condition on five consecutive attempts to operate the injector, combined with battery voltage above 9 volts DC for 2 seconds.
Common causes of 46
- Damaged, corroded, or chafed connectors and/or wiring to the No. 4 injector
- A general problem within the wiring harness, including an open or short circuit affecting one or more cylinders
- A short circuit in the return wire for the injector circuit
- A fault in the wiring between the ECM and the valve cover base
- A faulty electronic unit injector on cylinder No. 4
- A faulty ECM, particularly if a short exists in common internal wiring shared with other injectors
How to troubleshoot CAT Engine 46: first checks
- Confirm the engine is at normal operating temperature before testing, since injector solenoid problems often show up once the engine is warmed up and under vibration from heavy load
- Inspect all connectors and wiring related to the No. 4 injector circuit for damage, corrosion, or loose pins, paying close attention to connections that may only fault under vibration
- Run an injector cutout test; a faulty electronic unit injector will show a noticeably low reading compared to the other cylinders
- Check the wiring harness between the ECM and the connector for an open circuit, and inspect wiring from the connector back to the ECM for damage
- Check for a short in the return wire and in any wiring shared between cylinders inside the ECM harness
- If wiring and connectors check out, suspect a faulty injector on cylinder No. 4; if the fault persists across multiple injectors sharing common ECM wiring, suspect the ECM itself
How the code clears
No separate clearing step is listed beyond correcting the underlying fault. Repair or replace damaged connectors, wiring, or the harness as needed, and confirm the harness between the ECM and the connector has no open circuit. Once the short circuit is corrected, the ECM should be able to fire the injector normally on subsequent attempts; the code should stop being generated once the electrical fault is resolved.
Affected models and serial ranges
46 appears in our records across 3 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 |
Frequently asked questions
What does CAT fault code 46 mean?
It means the ECM detected a short circuit, a high current condition, on the wiring or solenoid for the No. 4 cylinder electronic unit injector on a C13, C15, or C18 engine. SPN 654 identifies the No. 4 injector circuit and FMI 6 identifies the current-above-normal (short circuit) failure type.
Can I keep driving or working with fault code 46 active?
The engine will typically still run, but expect low power and rough running since one injector is not firing correctly. It is best to get it diagnosed as soon as practical rather than running it for an extended period, since the affected cylinder is not contributing properly to power output.
Why does this fault only show up when the engine is warm?
Injector solenoid wiring and connector problems often only reveal themselves once the engine reaches normal operating temperature and is under load and vibration. A connector that looks fine when cold can develop a short once things heat up and shake.
How do I tell if it's the injector or the wiring?
Start by inspecting connectors and wiring for damage or corrosion, then run an injector cutout test. A faulty injector will show a distinctly low reading compared to the other cylinders during that test, which points toward the injector itself rather than the harness.
Can a short in the ECM affect more than one cylinder?
Yes. If the short is in wiring that is common inside the ECM, it can affect other injectors sharing that circuit, two injectors on four cylinder engines or three injectors on six cylinder engines. If multiple injector codes appear together, the ECM or shared wiring is a likely cause.
What voltage does the ECM use to fire the injectors?
The ECM sends 105 volt pulses to each injector solenoid, timed and durated for the current engine load and speed. Code 46 sets when the ECM sees a high current, short circuit condition on that circuit along with battery voltage above 9 volts DC for 2 seconds.
Will the check engine or warning light come on for code 46?
Where equipped, a warning light or a warning message on the control panel display will come on and the ECM will log the diagnostic code when this fault is detected.