CAT 35 Fault Code: Engine Injector Cylinder #03 : Current Below Normal
Engine Injector Cylinder #03 : Current Below Normal · ai-assisted, editor-reviewed · Last updated 2026-07-21
TL;DR
CAT code 35 (SPN 653 FMI 5) means the ECM detected low current flow, an open circuit, on the cylinder #3 injector solenoid circuit on C13 and C15 engines. The ECM keeps trying to fire the injector while the fault is active, but that cylinder is running on a compromised or dead injector signal until the open is fixed.
Medium severity. The engine will typically keep running since the ECM keeps attempting to fire the injector, but you lose proper combustion control on cylinder #3, which brings rough running, power loss, and possible increased wear until it's fixed. Treat it as a diagnose-this-shift issue rather than an immediate shutdown, unless rough running or power loss is severe enough to affect safe operation.
What does CAT error code 35 mean?
Fault code 35, SPN 653 FMI 5, is set on CAT C13 and C15 engines when the ECM detects low current flow through the cylinder #3 injector solenoid circuit, which it interprets as an open circuit. These engines use Electronic Unit Injectors (EUI) with a solenoid in each injector. The ECM sends 105 V pulses to each injector solenoid at a timing and duration matched to engine load and speed. When the ECM doesn't see the current flow it expects on that circuit, it flags the open and keeps trying to fire the injector anyway.
This is the low-current, open-circuit counterpart to code 36, which covers the same injector and circuit but for high current flow (a short circuit). Where code 36 has the ECM disabling the solenoid to protect it from short-circuit damage, code 35 is about a circuit that isn't completing at all, so the ECM just keeps trying and getting nothing back.
Because the ECM continues attempting to fire the injector while this code is active, the engine usually keeps running, but cylinder #3 is not firing correctly. Expect rough idle, a miss, reduced power, or increased vibration, especially under load.
Common causes of 35
- A failed injector, meaning the solenoid winding itself has failed open inside the injector
- A wiring problem between the ECM and the valve cover, such as a broken conductor, corroded connector, or backed-out pin
- A wiring problem under the valve cover in the injector harness itself, which is exposed to heat and vibration in that location
- A plugged oil outlet port on the exhaust valve rocker arm, which is listed as a related mechanical cause for this code
How to troubleshoot CAT 35: first checks
- Run the engine up to normal operating temperature before testing. CAT notes that injector solenoid problems typically show up once the engine is warmed up and under load or vibration, so testing cold can hide the fault.
- Inspect the wiring and connectors between the ECM and the valve cover carefully, looking for chafing, corrosion, loose pins, or damage that might only reveal itself when the harness is flexed or under vibration.
- Pull the valve cover and inspect the injector harness wiring underneath it for chafed insulation, broken strands, or connector corrosion at the injector itself.
- Wiggle-test harness sections and connectors while watching for the fault to reappear or the engine to stumble, since intermittent opens often only show up under vibration or heat.
- Check the oil outlet port on the exhaust valve rocker arm for cylinder #3 for blockage, since a plugged port is listed as a possible cause tied to this code.
- If wiring and connectors check out, test the injector solenoid itself for continuity and resistance to determine if the injector has failed internally.
How the code clears
No separate clearing step or reset procedure is listed for this code. Once the open circuit is repaired, whether that's a wiring repair, a connector fix, or an injector replacement, the code should stop being active on its own as the ECM sees normal current flow return on the circuit.
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 fault code 35 mean?
It means the ECM detected low current flow, essentially an open circuit, on the cylinder #3 injector solenoid circuit on a C13 or C15 engine. The ECM keeps trying to fire the injector while this condition is active.
Will the engine still run with code 35 active?
Usually yes, since the ECM keeps attempting to fire the injector even with the fault present. Expect rough running, a miss, or reduced power from cylinder #3 rather than a hard shutdown.
What's the difference between code 35 and code 36?
Both cover the cylinder #3 injector solenoid circuit, but code 35 is low current flow, an open circuit, where the ECM keeps trying to fire the injector. Code 36 is high current flow, a short circuit, where the ECM disables the solenoid circuit to prevent damage and periodically retries. If your symptom looks like a short rather than an open, check the code 36 page instead.
What are the most common causes of code 35?
CAT lists four: a failed injector, wiring problems between the ECM and the valve cover, wiring problems under the valve cover in 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?
CAT notes that injector solenoid wiring and connector problems typically surface once the engine reaches normal operating temperature and is under load or vibration. That's why diagnostic checks should be done at normal operating temperature, not cold.
Is a plugged rocker arm oil port really related to an electrical fault code?
CAT lists it as a related cause for this code, likely because of how it affects that cylinder's valve train and injector operation mechanically, even though the code itself is triggered by an electrical current reading.
Do I need special tools to diagnose code 35?
A basic multimeter for continuity and resistance checks on the wiring and injector solenoid, along with a careful visual and wiggle-test inspection of the harness and connectors, covers the checks CAT points to for this code.