CAT Engine 2915 Fault Code: Engine Cooling Fan Solenoid open circuit
Also called Engine Cooling Fan Solenoid - Current Below Normal, Engine Cooling Fan Solenoid : Current Below Normal, Engine Cooling Fan Solenoid Current Below Normal, Engine Cooling Fan Solenoid Open Circuit, Engine Cooling Fan Solenoid current below normal, Engine Cooling Fan Solenoid:Current Below Normal, Engine Cooling Fan Solinoid : Current Below Normal, Fan Drive Bypass Command Status : Current Below Normal
Engine Cooling Fan Solenoid open circuit · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 2915 (SPN 4212 / FMI 5) means the ECM has detected an open circuit or a short to battery in the engine cooling fan control solenoid circuit. The ECM responds by sending minimum current to the solenoid, which forces the fan pump to maximum pressure and drives the cooling fan at maximum speed until the fault is fixed.
Medium severity. The engine keeps running and the fan defaults to maximum speed, so overheating from a stuck fan is unlikely. The bigger concerns are wasted fuel, added noise, and unnecessary load on the fan drive system until the wiring or solenoid problem is repaired.
What does CAT Engine error code 2915 mean?
Code 2915 points to the wiring and solenoid that control engine cooling fan speed on C11, C13, C15, C18, C27, and C32 engines. The ECM normally varies current to the fan control solenoid to keep the fan at the rpm needed for the current coolant temperature, intake air temperature, and hydraulic oil temperature, all while trying to save fuel and cut noise.
The fan control solenoid adjusts a hydraulic pump that supplies oil to the fan motor. Less current to the solenoid means less oil is bypassed, so the pump drives the fan faster. More current means more bypass and a slower fan. The ECM aims to hold fan speed within ± 50 rpm of the target using feedback from a cooling fan pump pressure sensor or a cooling fan speed sensor, depending on the engine.
When the ECM detects an open circuit or a short to battery voltage in this solenoid's wiring, it can no longer control fan speed normally. As a protective default, it sends minimum current to the solenoid, which pushes the fan pump to maximum pressure and the fan to maximum speed for as long as the fault is active. The code is logged so it can be pulled with a diagnostic scan tool.
What triggers a CAT Engine 2915 code?
The ECM sets this code when it detects an open circuit and/or a short to +Battery in the engine fan control solenoid circuit. On some engine families the solenoid receives current on J2-19 with its return on J2-7, and the control signal is a pulse width modulated current operating between 15 and 27 VDC and 0.1 and 1.8 amperes (0.0 to 1.4 amperes on other descriptions, representing maximum to minimum fan rpm).
Common causes of 2915
- Damaged, corroded, or disconnected connector, pin, or socket at the fan control solenoid or ECM connector
- Chafed, pinched, or abraded wiring in the harness between the ECM and the fan control solenoid
- Short circuit between the fan control solenoid harness connector and the ECM
- Open circuit between the ECM and the connector for the fan control solenoid
- Faulty or worn engine fan control solenoid that needs replacement
- Faulty ECM that needs replacement (checked only after wiring, connectors, and the solenoid are ruled out)
How to troubleshoot CAT Engine 2915: first checks
- Inspect the connectors at the fan control solenoid and at the ECM for corrosion, bent pins, or a loose coupling. Reseat and clean any suspect connections.
- Trace the harness between the ECM and the solenoid for signs of chafing, pinching, or abrasion, especially anywhere it runs near moving parts or sharp edges.
- Check for a short to battery voltage on the solenoid circuit wiring using a diagnostic scan tool and appropriate electrical test procedures.
- Confirm the fan is actually running at maximum speed as expected when the code is active, which supports that the ECM's default fail-safe response is working.
- If wiring and connectors check out, test the solenoid itself and consider swapping in a known-good unit before condemning the ECM.
How the code clears
No separate clearing procedure is listed for this code beyond repairing the underlying open circuit or short to battery. Once the wiring, connector, or solenoid fault is corrected and the ECM no longer detects the open or short condition, the fan should return to normal ECM-controlled speed. A diagnostic scan tool can be used to confirm the code is no longer active and, where supported, to run a manual override test of the fan from minimum to maximum speed to verify solenoid response.
Affected models and serial ranges
2915 appears in our records across 6 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C11 | Serial range not listed in source records |
| 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 2915 mean on my engine?
It means the ECM has found an open circuit or a short to battery voltage in the engine cooling fan control solenoid circuit. The ECM can no longer vary fan speed normally, so it sends minimum current to the solenoid, which forces the fan pump to maximum pressure and runs the fan at maximum speed.
Is it safe to keep operating with code 2915 active?
The engine can typically keep running because the fan defaults to maximum speed, which protects against overheating. However, you will likely notice more noise and reduced fuel economy, and the underlying wiring or solenoid fault should be diagnosed and repaired as soon as practical.
Why is my cooling fan running at full speed all the time?
This is the ECM's designed fail-safe response to code 2915. When it detects an open or shorted solenoid circuit, it deliberately sends minimum current to the solenoid so the fan pump defaults to maximum pressure and the fan runs at maximum speed until the fault is fixed.
What parts commonly cause code 2915?
Damaged or corroded connectors and pins, chafed or pinched wiring in the harness, a short between the solenoid harness connector and the ECM, an open circuit between the ECM and the solenoid connector, a worn fan control solenoid, or, less commonly, a faulty ECM.
Can I use a scan tool to test the fan solenoid for this code?
Yes. A diagnostic scan tool supports a manual override that lets you command the fan from minimum to maximum rpm, which is useful for confirming whether the solenoid and wiring respond correctly once repairs are made.
Which CAT engines use this fault code?
Code 2915 (SPN 4212 / FMI 5) applies to the C11, C13, C15, C18, C27, and C32 engine families that use an ECM-controlled hydraulic cooling fan drive.