CAT Engine 26106 Fault Code: Cylinder #5 Injector Actuator #2:Current Above Normal
Also called Cylinder #5 Injector Actuator #2 - Current Above Normal, Cylinder #5 Injector Actuator #2 : Current Above Normal
Cylinder #5 Injector Actuator #2:Current Above Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 26106 (SPN 3663 / FMI 6) means the ECM detected high current flow in the #2 solenoid circuit of the Cylinder #5 injector on C13, C15, C18, C27, and C32 engines. The ECM shuts the solenoid circuit off to prevent damage, then keeps trying to fire it periodically until the short is fixed.
High severity. The engine can keep running but will misfire or lose power on cylinder #5 while the ECM repeatedly disables and retries the solenoid circuit. Left unresolved, the short circuit condition can damage the injector solenoid or ECM driver over time.
What does CAT Engine error code 26106 mean?
CAT C13, C15, C18, C27, and C32 engines use Electronic Unit Injectors (EUI) that are electronically controlled, and mechanically actuated in some versions. Each injector has two solenoids, and the ECM sends 105 volt pulses to each solenoid at the correct timing and duration for the current engine load and speed.
The ECM constantly monitors current flow through each solenoid circuit. Code 26106 sets specifically when high current flow is detected on the Cylinder #5 Injector Actuator #2 circuit. This tells the ECM there is likely a short in the wiring, connector, harness, or injector solenoid itself.
When the ECM sees this high current condition, it disables that solenoid circuit right away to prevent damage to the driver electronics. It does not just give up though: the ECM periodically attempts to fire the injector again. If the short is still there, the disable-and-retry cycle repeats over and over until the underlying problem is corrected.
Common causes of 26106
- Damaged, corroded, or shorted connectors or wiring in the injector solenoid circuit
- A short or fault in the wiring harness between the ECM and the connector, or between the ECM and the valve cover base
- A fault in the harness section running under the valve cover
- A faulty injector solenoid or a bad injector that needs replacement
- An intermittent wiring or connector problem that only shows up under heat or vibration
- A faulty ECM (less common, but listed as a possible cause if wiring and injector both check out)
How to troubleshoot CAT Engine 26106: 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/or under vibration from heavy load
- Inspect all connectors and wiring on the Cylinder #5 injector circuit for corrosion, chafing, melted insulation, or loose pins
- Wiggle-test the harness and connectors under load or simulated vibration conditions, since intermittent faults often only appear that way
- Check the harness between the ECM and the connector, and the section under the valve cover, for opens or shorts
- Inspect the injector solenoid itself for damage if wiring and connectors check out clean
- Verify ECM connections are secure and free of corrosion before considering ECM replacement
How the code clears
No separate clearing step is listed. Once the wiring, connector, harness, or injector fault causing the high current condition is repaired, the ECM should stop generating the code on its own as it continues its normal fire attempts on the solenoid circuit.
Affected models and serial ranges
26106 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 26106 mean?
It means the ECM detected current above normal (a short circuit condition) on the #2 solenoid circuit of the Cylinder #5 fuel injector. The ECM disables that circuit to protect itself and keeps trying to re-fire the injector periodically.
Can I keep running the engine with code 26106 active?
The engine will typically keep running, but cylinder #5 may misfire or lose power while the ECM cycles the solenoid circuit on and off. It is best to diagnose and repair the short as soon as practical to avoid further damage to the injector or ECM.
What usually causes this code?
Most cases trace back to damaged or corroded wiring and connectors, or a short somewhere in the harness between the ECM and the injector, including the section under the valve cover. A faulty injector solenoid or, less often, a faulty ECM can also cause it.
Why does this fault often show up only when the engine is warm or working hard?
Injector solenoid wiring problems are often heat- and vibration-related. A connector or wire that looks fine at idle and cold can develop an intermittent short once the engine reaches normal operating temperature or is under heavy load and vibration.
Is 26106 specific to one cylinder or injector solenoid?
Yes. This code is specific to the #2 solenoid on the Cylinder #5 injector. Each injector has two solenoids, and each one is monitored and coded separately, so other cylinders or the other solenoid on the same injector would trigger a different code.
Which CAT engines can set this code?
This code applies to the C13, C15, C18, C27, and C32 engine families, all of which use Electronic Unit Injector systems with the same 105 volt solenoid pulse design.
Do I need to replace the injector right away?
Not necessarily. Wiring, connector, and harness faults are common causes and should be ruled out first. Injector replacement is listed as a possible cause but is not the only fix, so check the electrical path thoroughly before condemning the injector.