CAT 35 Fault Code: Engine Injector Cylinder #03 : Current Below Normal
Engine Injector Cylinder #03 : Current Below Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 35, also identified as SPN 653 FMI 5, means the ECM detected low current flow (an open circuit) on the injector solenoid circuit for cylinder #3 on C13 and C15 engines. The ECM keeps trying to fire the injector, but the underlying wiring or injector problem needs to be found and fixed before it causes a misfire or rough running.
Medium severity. The engine will typically keep running because the ECM keeps attempting to fire the injector, but a dead or intermittent cylinder means lost power, rough running, and possible long-term damage if ignored. Diagnose it within the shift rather than continuing to run heavy loads on a misfiring cylinder.
What does CAT error code 35 mean?
Code 35 (SPN 653 FMI 5) fires when the ECM senses low current flow, essentially an open circuit, on the solenoid circuit for the #3 cylinder injector. These engines use Electronic Unit Injectors (EUI) that are electronically controlled, and each injector has its own solenoid. The ECM sends 105 V pulses to each injector solenoid at the correct time and duration for the engine's current load and speed.
When the ECM detects low current (open circuit) on this cylinder's injector solenoid, it logs the code but keeps trying to fire the injector anyway. This is different from a high current (short circuit) situation, where the ECM disables the solenoid circuit to prevent damage and then periodically retries firing it. For code 35 specifically, it's the low current, open circuit condition being flagged.
In plain terms, cylinder #3 isn't getting a proper electrical signal to its injector, so that cylinder may not be firing correctly or at all, which shows up as rough idle, lost power, or increased vibration under load.
Common causes of 35
- Failed injector on cylinder #3
- Damaged or disconnected wiring between the ECM and the valve cover
- Damaged or corroded wiring under the valve cover for the injector harness
- Plugged oil outlet port on the exhaust valve rocker arm
How to troubleshoot CAT 35: 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 under vibration from heavy loads
- Inspect wiring and connectors between the ECM and the valve cover for looseness, corrosion, chafing, or damage, paying close attention to connections that might only fail under vibration
- Open the valve cover and inspect the injector harness wiring for cylinder #3 for damage, corrosion, or loose connections
- Check the oil outlet port on the exhaust valve rocker arm for cylinder #3 to confirm it is not plugged
- Test the injector solenoid itself for cylinder #3 to determine if it has failed and needs replacement
How the code clears
No separate clearing step is listed. Once the failed component, whether it's the injector, the wiring between the ECM and valve cover, the wiring under the valve cover, or the plugged rocker arm oil port, is repaired or replaced, the code should stop being active. Confirm the repair by running the engine at operating temperature and under load to make sure the fault does not return.
Affected models and serial ranges
35 appears in our records across 2 CAT 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 |
Frequently asked questions
What does CAT code 35 mean?
It means the ECM detected low current flow, an open circuit condition, on the injector solenoid circuit for cylinder #3 on a C13 or C15 engine. The ECM continues trying to fire that injector while the code is active.
Is it safe to keep running the engine with code 35 active?
The engine will typically keep running since the ECM keeps attempting to fire the injector, but running with a misfiring or non-firing cylinder for long periods risks uneven wear, lost power, and potential damage. It should be diagnosed and repaired promptly rather than ignored.
What usually causes this code?
CAT lists four causes: a failed injector, damaged wiring between the ECM and the valve cover, damaged wiring under the valve cover for the injector harness, or a plugged oil outlet port on the exhaust valve rocker arm.
Why does this fault often show up only when the engine is warm?
Problems with an injector solenoid circuit typically occur once the engine reaches normal operating temperature and is under vibration from heavy loads, so intermittent wiring or connector issues may not show up on a cold, unloaded engine.
How many volts does the ECM send to the injector solenoid?
The ECM sends 105 V pulses to each injector solenoid, timed and sized for the current engine load and speed.
Does code 35 disable the injector?
No. For a low current, open circuit condition like code 35, the ECM keeps trying to fire the injector. The ECM only disables the solenoid circuit when it detects high current, a short circuit, condition instead.
What's the difference between code 35 and a short circuit code on the same injector?
Code 35 is the low current, open circuit version of the fault. A high current, short circuit condition on the same injector would cause the ECM to disable the solenoid circuit and periodically retry firing it, which is a related but separate condition.