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 2026-07-21
TL;DR
CAT code 26106 (SPN 3663 / FMI 6) means the ECM detected excessive current flow through the #2 solenoid circuit of the #5 cylinder's electronic unit injector, and has disabled that solenoid circuit to prevent damage, retrying it periodically until the short is fixed.
High severity. The ECM shuts down the affected solenoid circuit to protect it from a short, which means that cylinder is not firing correctly on that actuator. This causes rough running, power loss, and possible misfire, and repeated short-circuit cycling can damage the injector or ECM driver over time if left unaddressed.
What does CAT Engine error code 26106 mean?
CAT engines with Electronic Unit Injectors (EUI) use two solenoids per injector. The ECM sends 105 volt pulses to each solenoid at the correct time and duration for the current engine load and speed.
The ECM constantly monitors current flow through each solenoid circuit. Code 26106 sets when the ECM detects current flow that is too high on the #2 actuator solenoid of the #5 cylinder injector. To protect the driver circuit from damage, the ECM disables that solenoid circuit but keeps periodically retrying to fire the injector. If the short is still present, this disable-and-retry cycle repeats until the wiring, connector, injector, or ECM problem is corrected.
This is different from a low current fault (open circuit), where the ECM keeps trying to fire without disabling anything. An above-normal current fault points to a short somewhere in that solenoid's circuit path.
Common causes of 26106
- A short circuit in the wiring or connectors between the ECM and the injector, often caused by chafed insulation contacting another powered wire
- Damaged or corroded connectors at the injector or in the harness
- A fault in the wiring harness between the ECM and the valve cover base, or in the harness routed under the valve cover
- An internal electronic fault in the injector solenoid itself, requiring injector replacement
- An intermittent short that only shows up when the engine is warmed up or under heavy load and vibration
- A faulty ECM driver circuit for that solenoid, in cases where wiring and injector both check out
How to troubleshoot CAT Engine 26106: first checks
- Run the engine to normal operating temperature before testing, since many of these shorts only appear when the engine is warm and under vibration or load
- Inspect the wiring harness between the ECM and the injector connector, and the harness section under the valve cover, for chafed insulation, pinched wires, or wire making contact with another powered circuit
- Check all connectors in the circuit path for corrosion, moisture intrusion, bent pins, or loose terminals
- Wiggle-test the harness and connectors while monitoring for the code to reappear, since intermittent shorts often only show up under vibration
- Measure resistance and continuity of the solenoid circuit wiring from ECM to injector to rule out a harness-internal short
- If wiring and connectors check out, test the injector solenoid itself, since an internal short in the injector requires replacement
- If the injector and harness both test good, suspect the ECM driver circuit for that solenoid
How the code clears
No separate clearing step is listed. Once the short circuit in the wiring, connector, injector, or ECM has been repaired, the ECM should stop disabling the solenoid circuit and the code should stop being active. Clear any stored code with your diagnostic tool and confirm the engine runs without the fault re-triggering, including under load and at operating temperature.
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 too much current flowing through the #2 solenoid circuit on the #5 cylinder's fuel injector, which points to a short circuit somewhere in that wiring path or in the injector itself.
Can I keep running the engine with this code active?
The ECM will keep retrying to fire the injector periodically, but that cylinder's #2 actuator is effectively disabled between retries, causing rough running and power loss. It is best to diagnose and repair as soon as practical rather than run it long term.
What is the difference between code 26106 and code 26105?
26105 is Current Below Normal for the same #5 cylinder Injector Actuator #2 circuit, which points to an open circuit or lost signal, not a short. 26106 is Current Above Normal, meaning the ECM sees a short and disables the circuit to protect it. Below-normal faults need open-circuit checks (broken wire, bad connection); above-normal faults need short-circuit checks (chafed wire touching power, internal short).
Is 26106 the same issue as 26126?
No. 26126 is the same Current Above Normal fault but for Cylinder #6 Injector Actuator #2 instead of Cylinder #5. The diagnostic approach is the same, just check the #6 cylinder's circuit and injector instead.
Why does this fault only show up sometimes?
Because the underlying short is often caused by chafed wiring or a loose connector that only makes contact when the engine is warm and vibrating under load. That is why the diagnostic procedure calls for testing at normal operating temperature and wiggle-testing the harness.
Do I need to replace the injector for this code?
Not necessarily. Wiring and connector problems are common causes and should be ruled out first. Injector replacement is only needed if the solenoid itself tests faulty after the harness and connectors are confirmed good.
Could the ECM itself be the cause of code 26106?
It is possible but less common. If the wiring harness, connectors, and injector all test good, the ECM's driver circuit for that solenoid should be suspected and the ECM may need to be replaced.