CAT Engine 26085 Fault Code: Cylinder #4 Injector Actuator #2:Current Below Normal
Also called Cylinder #4 Injector Actuator #2 - Current Below Normal, Cylinder #4 Injector Actuator #2 : Current Below Normal
Cylinder #4 Injector Actuator #2:Current Below Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Code 26085 means the ECM detected low current on the #2 solenoid circuit of the Cylinder #4 injector. This affects C13, C15, C18, C27, and C32 engines with Electronic Unit Injectors. The ECM keeps trying to fire the injector when this happens, but the cylinder may misfire or run rough until the wiring, connector, injector, or ECM issue is fixed.
Medium severity. The engine will typically keep running because the ECM keeps attempting to fire the injector, but a misfiring cylinder causes rough running, power loss, and possible long-term damage if ignored. Diagnose within the shift rather than continuing to operate indefinitely.
What does CAT Engine error code 26085 mean?
Cylinder #4 on these Cat engines uses an Electronic Unit Injector (EUI) with two solenoids inside it. The ECM fires each solenoid with a 105 volt pulse, timed and sized for the engine's current load and speed. The ECM also watches the current flowing through each solenoid circuit as part of its self-check.
Code 26085 specifically flags the #2 solenoid in the Cylinder #4 injector when the ECM sees current flow below what it expects. When this happens, the ECM does not give up on that injector: it keeps trying to fire it on every cycle. That means the cylinder may still fire intermittently, but weakly or unreliably, which can show up as rough idle, a miss under load, or reduced power.
This is different from a high-current short fault, where the ECM disables the circuit outright to protect it. With a low-current code like 26085, the circuit stays active and the ECM continues attempting normal operation, so the symptom can be subtle until it gets worse.
Common causes of 26085
- Damaged, corroded, or loose connectors or wiring in the injector solenoid circuit
- An open circuit in the wiring harness between the ECM and the injector connector
- A faulty harness section between the ECM and the valve cover base, or under the valve cover itself
- An internal electronic problem with the injector solenoid itself, requiring injector replacement
- A faulty ECM, though this is generally the last cause to suspect after wiring and injector checks are done
- An intermittent connection issue that only shows up when the engine is warm or under vibration from heavy load
How to troubleshoot CAT Engine 26085: first checks
- Run the engine to normal operating temperature before testing, since these faults often only appear once the engine is warmed up
- Inspect all connectors and wiring on the Cylinder #4 injector circuit for corrosion, looseness, chafing, or damage, paying close attention since vibration-related faults may not show up at idle
- Wiggle-test the harness and connectors while the engine runs or while probing resistance, since the wiring may only fault out under vibration from heavy load
- Check the harness between the ECM and the injector connector, including the section between the ECM and the valve cover base and the section under the valve cover, for opens or damage
- If wiring and connectors check out, test the injector solenoid itself for proper resistance and operation
- Only after wiring, connectors, and injector are confirmed good should the ECM be considered as the fault source
How the code clears
No separate clearing step is listed for this code. Once the underlying wiring, connector, injector, or ECM problem is repaired, the code should stop being active as the ECM sees normal current flow again. No reset procedure beyond fixing the root cause is listed.
Affected models and serial ranges
26085 appears in our records across 5 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 |
| C27 | Serial range not listed in source records |
| C32 | Serial range not listed in source records |
Frequently asked questions
What does CAT code 26085 mean?
It means the ECM detected current flow below normal on the #2 solenoid inside the Cylinder #4 fuel injector. The injector uses two solenoids that the ECM pulses with 105 volts, and this code fires when one of those circuits isn't pulling the current the ECM expects.
Can I keep running the engine with code 26085 active?
The ECM will keep trying to fire the injector, so the engine will likely keep running, but expect rough running, a miss, or power loss from that cylinder. It's best to diagnose and repair it within the same shift rather than running it indefinitely.
What usually causes this code?
Most often it's damaged, corroded, or loose wiring and connectors in the injector circuit, or an open in the harness between the ECM and the injector. Less commonly it's a bad injector solenoid, and rarely a faulty ECM.
Why does this fault only show up sometimes?
These faults commonly appear once the engine is warmed up and under vibration from heavy load. A wire or connector that looks fine at idle can open up intermittently once the engine is hot and shaking under load, so testing cold or at idle only may miss the problem.
Which engines does code 26085 apply to?
It applies to Cat C13, C15, C18, C27, and C32 engines equipped with Electronic Unit Injectors.
Do I need to replace the injector for this code?
Not necessarily. Wiring and connector problems are more common causes than a bad injector. Check and repair the wiring and connectors first, then test the injector solenoid itself before considering injector replacement.
Is the ECM likely the problem?
The ECM is listed as a possible cause, but it should be the last thing checked. Confirm the wiring, connectors, and injector solenoid are all good before replacing the ECM.