CAT Engine 26105 Fault Code: Cylinder #5 Injector Actuator #2:Current Below Normal
Also called Cylinder #5 Injector Actuator #2 - Current Below Normal, Cylinder #5 Injector Actuator #2 : Current Below Normal
Cylinder #5 Injector Actuator #2:Current Below Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Code 26105 means the ECM detected low current flow on the #2 solenoid circuit of the cylinder #5 injector. This points to a wiring, connector, or injector solenoid problem, and in some cases an ECM fault, on C13, C15, C18, C27, and C32 engines.
High severity. The engine will keep running and the ECM will keep trying to fire the injector, but a misfiring or dead cylinder means rough running, power loss, and possible long-term damage if the wiring or injector issue is not corrected. Diagnose before continuing heavy-load operation.
What does CAT Engine error code 26105 mean?
These CAT engines use Electronic Unit Injectors (EUI) that are electronically controlled, and each injector has two solenoids. The ECM sends 105 volt pulses to each solenoid at the correct time and duration for the current engine load and speed. This code specifically covers the #2 solenoid circuit on the cylinder #5 injector.
The ECM constantly monitors current flow through each solenoid circuit. When it sees current flow that is lower than expected, it sets this code and keeps trying to fire the injector anyway. This is different from a high-current short circuit fault, where the ECM actually disables the solenoid circuit to protect it and only tries firing periodically.
Because the ECM keeps attempting to fire the injector even with low current detected, the cylinder may still be getting some fuel delivery, but it will likely be inconsistent, which shows up as rough idle, power loss, or a noticeable miss under load.
Common causes of 26105
- 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 fault in the harness section under the valve cover or between the ECM and the valve cover base
- A faulty injector solenoid or a bad injector that needs replacement
- An intermittent electrical problem that only shows up when the engine is warm or under vibration from heavy load
- A faulty ECM (less common, but listed as a possible cause)
How to troubleshoot CAT Engine 26105: first checks
- Bring the engine to normal operating temperature before testing, since problems with injector solenoids typically show up once the engine is warmed up and under load or vibration
- Inspect all connectors and wiring in the cylinder #5 injector circuit for corrosion, looseness, chafing, or damage, paying close attention since intermittent faults often only appear under vibration
- Check the wiring harness between the ECM and the injector connector for continuity to rule out an open circuit
- Inspect the harness section under the valve cover and between the ECM and valve cover base for damage
- Wiggle-test wiring and connectors while monitoring for the fault to catch vibration-induced intermittent faults
- If wiring and connectors check out, test the injector solenoid itself, and consider injector replacement if it is faulty
How the code clears
No separate clearing step is listed. Once the underlying wiring, connector, injector, or ECM problem is repaired, the ECM should stop detecting low current on the circuit and the code should not reset on its own.
Affected models and serial ranges
26105 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 26105 mean?
It means the ECM detected current flow lower than expected on the #2 solenoid circuit of the cylinder #5 injector. The ECM keeps trying to fire the injector even with this fault active.
Which CAT engines can show code 26105?
This code applies to C13, C15, C18, C27, and C32 engines that use Electronic Unit Injectors.
Can I keep running the engine with this code active?
The engine will typically keep running because the ECM keeps trying to fire the injector, but expect rough running, misfire, or power loss on that cylinder. It should be diagnosed and repaired rather than ignored, especially under heavy load.
What usually causes low current on an injector solenoid circuit?
The most common causes are damaged or corroded wiring and connectors, or an open circuit somewhere in the harness between the ECM and the injector. A faulty injector solenoid or, less commonly, a faulty ECM can also be the cause.
Why does this problem often show up only when the engine is warm?
Because wiring and connector issues that cause this fault are often intermittent and tied to heat expansion or vibration under load. Testing at normal operating temperature, and while wiggling harness connectors, helps reproduce the fault.
Is this the same as a short circuit code on the injector?
No. This code is for low current (an open or high-resistance type condition), which is different from a high current short circuit fault, where the ECM actually disables the solenoid circuit to prevent damage.
Do I need to replace the injector to fix code 26105?
Not necessarily. Wiring and connector repairs resolve many cases. Injector replacement is only needed if the solenoid itself is confirmed faulty after wiring and harness checks come back clean.