CAT Engine 35 Fault Code: Cylinder #3 Injector : Current Below Normal
Also called Cylinder #3 Injector - Current Below Normal, Cylinder #3 Injector Current Below Normal, Cylinder #3 Injector current below normal, Cylinder #3 Injector: Current Below Normal, Engine Injector Cylinder #03 : Current Below Normal
Cylinder #3 Injector : Current Below Normal · ai-assisted, editor-reviewed · Last updated 2026-07-21
TL;DR
Fault code 35 (SPN 653 FMI 5) means the ECM sees an open circuit or low current condition on the No. 3 cylinder injector solenoid circuit. It sets after five consecutive failed attempts to fire the injector while battery voltage stays above 9 volts DC for 2 seconds. Expect low power and rough running until it's fixed.
Medium severity. The engine keeps running and the ECM keeps trying to fire the injector, but you lose that cylinder's contribution, so expect low power, rough running, and possible vibration under load. It won't strand you immediately, but leaving one injector dead long-term stresses the ECM's driver circuit and other cylinders. Diagnose within the shift, sooner if the rough running is severe.
What does CAT Engine error code 35 mean?
Fault code 35 (SPN 653 FMI 5) applies to C13, C15, and C18 engines with Electronic Unit Injectors (EUI). Each injector has a solenoid on top of the injector body, and the ECM fires it with a precisely timed pulse for the engine's current load and speed. This code is the 'current below normal' or open-circuit version: the ECM isn't seeing enough current flow through the No. 3 injector solenoid circuit to know the injector actually fired.
This is fundamentally different from a short circuit or high-current fault. Here the circuit path is broken, starved, or otherwise not carrying current the way it should, whether that's a wiring break, a bad connector, a failed solenoid winding, or an internal ECM issue on the shared driver circuit.
Because the ECM shares common wiring between certain cylinders inside the ECM itself, a fault on that shared wiring can knock out more than just cylinder #3. On six-cylinder engines, three injectors can share common ECM wiring, so if you're seeing rough running across more than one cylinder along with this code, look at the shared circuit, not just the #3 injector in isolation.
What triggers a CAT Engine 35 code?
The ECM logs code 35 when it detects a low current (open circuit) condition on five consecutive attempts to fire the No. 3 injector solenoid, while battery voltage stays above 9 volts DC for 2 seconds. Once logged, the ECM keeps attempting to fire the injector, but the open circuit prevents it from actually operating.
Common causes of 35
- Damaged, corroded, or loose connectors and wiring in the No. 3 injector circuit
- A general fault in the wiring harness between the ECM and the injector connector
- An open circuit specific to the No. 3 cylinder's wiring
- A short circuit in the cylinder wiring (also logged under this code family)
- A fault at the connection between the ECM and the valve cover base
- A short in the return wire for the injector circuit
- A faulty No. 3 electronic unit injector (solenoid winding failure)
- A faulty ECM, particularly if the issue is on wiring shared internally between multiple cylinders
How to troubleshoot CAT Engine 35: first checks
- Inspect the No. 3 injector connector and harness for corrosion, loose pins, or chafed insulation, this is the open-circuit code, so you're hunting for broken continuity, not a dead short to power
- Check for continuity through the full length of the injector solenoid circuit from the ECM connector to the injector, looking specifically for an open (infinite resistance) rather than a short
- Wiggle-test the harness and connectors while watching for the fault to appear, since problems often show up only when the engine is warmed up and under vibration from heavy load, not at idle or cold
- Verify battery voltage is stable and above 9 volts DC, since the ECM needs that voltage present for 2 seconds to confirm the fault condition rather than a low-voltage dropout
- Run an injector cutout test if available: a faulty No. 3 injector will show a noticeably low reading compared to the other cylinders
- Check the connection between the ECM and the valve cover base for damage or looseness
- If more than one cylinder is affected along with #3, inspect the shared common wiring inside the harness near the ECM, since a fault there can take out multiple injectors that share that circuit
- If wiring and connectors check out clean, suspect the injector itself or, as a last resort, the ECM
How the code clears
No separate clearing step is listed for this code. Once the open circuit is repaired, the ECM should stop logging new occurrences on subsequent injector firing attempts; clear the code with your diagnostic tool and confirm it does not return under a load test or after the engine reaches normal operating temperature.
Affected models and serial ranges
35 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 35 mean?
It means the ECM detected a low current or open circuit condition on the No. 3 cylinder injector solenoid circuit, on five consecutive attempts to fire that injector, while battery voltage held above 9 volts DC for 2 seconds. It's logged as SPN 653 FMI 5.
Can I keep running the engine with fault code 35 active?
The engine will keep running since the ECM keeps trying to fire the injector, but expect low power and rough running. It's not an immediate stop-now situation, but running long-term on a dead cylinder isn't good for overall engine balance or the ECM driver circuit, so get it diagnosed within the shift.
Why does this fault only show up when the engine is warmed up or under load?
Wiring and connector problems, especially chafed insulation or a marginal connector pin, often only open up under the heat expansion and vibration that come with a warmed-up engine under heavy load. That's why a wiggle test at operating temperature is more useful than checking cold at idle.
How is code 35 different from code 36?
Code 35 (this page) is 'Current Below Normal', an open circuit or low current fault. Code 36 is 'Current Above Normal', which points to a short circuit or excess current draw instead. They are opposite electrical failure modes on the same No. 3 injector circuit, so if your injector is drawing too much current rather than too little, you want the code 36 page.
Could this code affect more than just cylinder #3?
Yes. On engines where cylinders share common wiring inside the ECM, an open circuit on that shared wiring can knock out multiple injectors at once, up to three on six-cylinder engines. If you're seeing rough running beyond just one cylinder, check the shared circuit, not only the #3 injector wiring.
What's the difference between code 35 and code 32?
Code 32 covers erratic, intermittent, or incorrect injector operation, while code 35 specifically points to a sustained low-current, open-circuit condition detected over five consecutive firing attempts. If your symptoms are intermittent rather than a consistent open, code 32 is the more relevant page.
Will an injector cutout test help diagnose this fault?
Yes. When you run a cutout test, a faulty No. 3 injector tied to this fault will show a noticeably low reading compared to the other cylinders, which helps confirm whether the problem is the injector itself versus the wiring or connectors.