CAT Engine 26026 Fault Code: Cylinder #1 Injector Actuator #2:Current Above Normal
Also called Cylinder #1 Injector Actuator #2 - Current Above Normal, Cylinder #1 Injector Actuator #2 : Current Above Normal
Cylinder #1 Injector Actuator #2:Current Above Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 26026 (SPN 3659 / FMI 6) means the ECM detected current above normal on the #2 solenoid circuit of the cylinder #1 injector. This affects C13, C15, C18, C27, and C32 engines with Electronic Unit Injectors, and it usually points to a wiring, connector, injector, or ECM problem on that solenoid circuit.
High severity. The ECM disables the affected solenoid circuit when it detects high current to prevent damage, then periodically retries firing the injector. This causes rough running, power loss, or a misfire on that cylinder, and repeated retries with a persistent short can stress the ECM output driver. It should be diagnosed promptly rather than run indefinitely.
What does CAT Engine error code 26026 mean?
This code applies to CAT engines using Electronic Unit Injectors (EUI) that are electronically controlled. Each injector has two solenoids, and the ECM sends 105 volt pulses to each solenoid at the correct time and duration for the current engine load and speed. Code 26026 is specific to the #2 solenoid actuator on the cylinder #1 injector.
The ECM continuously monitors current flow through each solenoid circuit. If current flow is too low, a diagnostic code sets and the ECM keeps trying to fire the injector. If current flow is too high, a diagnostic code sets and the ECM disables that solenoid circuit to prevent damage from the excess current. The ECM will then periodically attempt to fire the injector again. If the short circuit condition is still present, this on-off cycle repeats until the underlying problem is fixed.
Because this cycle involves the ECM shutting down and restarting the circuit, the affected cylinder can run poorly, misfire, or drop out intermittently, especially when the fault is heat or vibration related.
Common causes of 26026
- Damaged, corroded, or loose connectors or wiring on the injector solenoid circuit
- An open or short circuit in the harness between the ECM and the injector connector, including sections under or near the valve cover base
- A faulty or worn injector solenoid, or a bad injector that needs replacement
- An electronic problem within the injector itself
- An intermittent fault that only shows up under vibration or once the engine reaches normal operating temperature
- A faulty ECM, in cases where wiring, connectors, and the injector all check out good
How to troubleshoot CAT Engine 26026: first checks
- Run the engine to normal operating temperature before testing, since these faults often only appear once the engine is warmed up or under load and vibration
- Inspect the wiring harness and connectors on the cylinder #1 injector circuit closely for corrosion, chafing, loose pins, or damage, paying particular attention to areas that flex or vibrate under load
- Check the harness routing between the ECM and the injector connector, and between the connector and the valve cover base, for opens or intermittent shorts
- Wiggle-test the harness and connectors while monitoring for the fault, since problems tied to vibration may not show up with the engine sitting still
- Test the injector solenoid itself once wiring and connectors are confirmed good, and be prepared to replace the injector if it fails testing
- If wiring, connectors, and the injector all test good, suspect the ECM as the last item to check or replace
How the code clears
No separate clearing step is listed. Once the wiring, connector, injector, or ECM problem causing the high current condition is repaired, the ECM should stop disabling the solenoid circuit and the code should stop being active. Confirm the repair by running the engine through the same conditions (warmed up, under load or vibration) that originally triggered the fault.
Affected models and serial ranges
26026 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 26026 mean?
It means the ECM detected current above normal on the #2 solenoid circuit of the cylinder #1 fuel injector. The ECM disables that solenoid circuit to prevent damage and periodically tries to fire the injector again.
Which CAT engines can show fault code 26026?
This code applies to CAT C13, C15, C18, C27, and C32 engines equipped with Electronic Unit Injectors.
Can I keep running the machine with this code active?
It is not recommended. The affected cylinder will misfire or lose power as the ECM cycles the solenoid circuit on and off, and running with a persistent short repeatedly stresses the ECM output driver. Diagnose and repair it as soon as practical.
Why does this fault only show up when the engine is warm or working hard?
Wiring and connector problems often only reveal themselves under heat expansion or vibration from engine load. That is why CAT recommends performing diagnostic checks with the engine at normal operating temperature and, where possible, under conditions similar to when the fault occurs.
Is this a wiring problem or a bad injector?
It can be either. Causes range from damaged connectors and wiring, an open or short in the harness between the ECM and injector, a bad injector solenoid, to a faulty ECM in less common cases. Wiring and connectors should be checked first since they are the most common cause.
Does fixing the wiring clear the code automatically?
No separate clearing step is listed for this code. Once the underlying wiring, connector, injector, or ECM issue is repaired, the high current condition should stop occurring and the code should no longer be active.
What's the difference between code 26026 and a low current injector fault?
They come from the same monitoring system but represent opposite conditions. Low current flow on the solenoid circuit sets a different diagnostic code and the ECM simply keeps trying to fire the injector without disabling the circuit. High current, as with 26026, causes the ECM to disable the solenoid circuit to prevent damage.