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 2026-07-21
TL;DR
Fault code 46 (SPN 654 FMI 6) means the ECM has detected a high current, short circuit condition in the solenoid or wiring for the No. 4 cylinder electronic unit injector. The ECM sees this for five consecutive attempts to fire the injector while battery voltage stays above 9 volts DC for 2 seconds. Expect low power and rough running until it is fixed.
Medium severity. The engine will keep running with low power and/or rough running, and the ECM keeps trying to fire the injector periodically. It is not an immediate shutdown condition, but ignoring it risks ECM-side wiring damage and ongoing performance loss, so it should be diagnosed within the shift, not left indefinitely.
What does CAT Engine error code 46 mean?
Code 46 points to a high current, short circuit condition in the No. 4 cylinder electronic unit injector (EUI) circuit, either at the solenoid itself or somewhere in the wiring feeding it. These engines use EUIs where the ECM sends a pulse to each injector solenoid at the correct time and duration for the given load and speed. One version of the description notes each injector contains two solenoids and the ECM sends 105 volt pulses to each one.
The ECM constantly monitors current flow through each solenoid circuit. When it sees high current flow, it logs this code and, on some descriptions, disables that solenoid circuit to prevent damage from the excess current. It will still periodically retry firing the injector. If the short circuit is still present, this cycle of retry and fault repeats until the underlying wiring or component problem is corrected.
Because the No. 4 injector shares some wiring paths inside the ECM with other cylinders, a short in common circuitry can affect more than just cylinder 4. On four cylinder engines, a short in shared ECM wiring can take out two injectors together, and on six cylinder engines it can take out three injectors that share that wiring.
What triggers a CAT Engine 46 code?
The ECM sets this code when it detects a high current (short circuit) condition for each of five consecutive attempts to operate the No. 4 injector solenoid, while battery voltage is above 9 volts DC for 2 seconds.
Common causes of 46
- Damaged connectors and/or wiring to the No. 4 injector solenoid
- A problem within the wiring harness itself, separate from the connectors
- A faulty No. 4 electronic unit injector
- An open or short circuit in the cylinder wiring
- A fault in the wiring or connection between the ECM and the valve cover base
- A short in the injector's return wire
- A faulty ECM, particularly if the short is in wiring shared internally by multiple injector circuits
How to troubleshoot CAT Engine 46: first checks
- With the engine at normal operating temperature, inspect all connectors and harness wiring feeding the No. 4 injector solenoid for chafing, melted insulation, or corrosion, since a short to another powered circuit is what drives current above normal.
- Flex and wiggle the harness near the injector and along its run to the ECM while watching for the fault to reappear, since problems with wiring or connectors often only show up under vibration when the engine is warmed up and under load.
- Check the harness run between the ECM and the valve cover base for pinched, rubbed, or pinched-through wiring that could be shorting the solenoid or return wire to another conductor.
- Run an injector cutout test: a faulty No. 4 electronic unit injector will show a low reading compared to the other injectors.
- If wiring and connectors check out clean, suspect the injector solenoid itself or, less commonly, an internal ECM fault affecting the shared wiring for this cylinder's circuit.
How the code clears
No separate clearing step is listed for this code. The ECM will keep logging it and periodically retrying to fire the injector as long as the short circuit condition is present. Once the damaged wiring, connector, or injector is repaired, the fault should stop being logged on subsequent operation; verifying with an injector cutout test after repair is the practical way to confirm the fix.
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 high current, short circuit condition in the solenoid or wiring for the No. 4 cylinder electronic unit injector, seen across five consecutive attempts to fire it while battery voltage stayed above 9 volts DC for 2 seconds.
Can I keep driving or working with code 46 active?
The engine will typically keep running but with low power and/or rough running. It's not listed as an immediate shutdown fault, but the short circuit prevents that injector from firing properly, so performance and fuel efficiency will suffer until it's repaired.
Why does code 46 only show up when the engine is warmed up or under load?
Faults with the injector solenoid and its wiring commonly only appear once the engine is warmed up and under vibration from heavy loads, which is why wiggle-testing the harness at normal operating temperature is part of the diagnostic process.
How is code 46 different from code 42 on the same injector?
Code 42 covers erratic, intermittent, or incorrect behavior on the No. 4 injector circuit, while code 46 specifically flags a high current short circuit condition detected across five consecutive firing attempts with battery voltage confirmed above 9 volts DC. Code 46 is a distinct short circuit fault, not general erratic operation.
Is code 46 the opposite of a low current or open circuit fault?
Yes. Code 46 is a current above normal, short circuit condition. A low current or open circuit condition on the same injector would be a different fault code entirely, since the ECM tracks high current and low current conditions separately for each injector solenoid.
Could a bad ECM cause code 46 instead of wiring or the injector?
Yes, some descriptions list a faulty ECM as a possible cause, especially since a short in wiring shared internally by multiple injector circuits within the ECM can affect more than one cylinder at once. This is usually checked only after ruling out connectors, harness wiring, and the injector itself.
Will a code 46 injector fault affect other cylinders too?
It can. Since some injector wiring is shared inside the ECM, a short in that common wiring can knock out two injectors together on four cylinder engines, or three injectors together on six cylinder engines, not just the No. 4 cylinder alone.