CAT Engine 914 Fault Code: Throttle Position Sensor : Voltage Below Normal
Also called Accelerator Pedal Position #1 : Voltage Below Normal, Throttle Position Sensor - Voltage Below Normal, Throttle Position Sensor voltage below normal, Throttle Position Sensor: Voltage Below Normal, Throttle Position Sensor:Voltage Below Normal
Throttle Position Sensor : Voltage Below Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Code 914 (SPN 91 / FMI 4) means the CAT ECM sees a throttle position sensor signal voltage that is below normal. This affects the accelerator pedal circuit on C13, C15, C18, C27, and C32 engines. The engine will default to a limp home speed if no functional throttle input is available.
High severity. The engine can lose normal throttle response and drop to a limp home speed until the fault is fixed. This is not an immediate shutdown risk, but it limits engine speed and can affect machine productivity and safety in traffic or lifting operations, so it should be diagnosed the same shift it appears.
What does CAT Engine error code 914 mean?
Code 914 points to the throttle position sensor circuit, the part of the system that tells the ECM how far the operator has pressed the accelerator pedal. The sensor is mounted on the pedal assembly and sends a PWM (pulse width modulated) signal whose duty cycle changes with pedal position: minimum duty cycle at released pedal, maximum duty cycle at full throttle. The ECM reads that signal and converts it to a throttle position of 0 percent to 100 percent.
The sensor itself cannot be adjusted. It runs on 8.0 ± 0.4 VDC supplied by the ECM, with a separate digital return also provided by the ECM. The ECM also runs an automatic calibration function at powerup that adjusts for the sensor's normal duty cycle range and minimizes deadband, so a wiring or supply problem can throw this calibration off just as easily as a bad sensor.
When the ECM sees the signal voltage drop below the normal range, it logs code 914 and, on machines with dual throttle inputs, switches over to the other throttle (primary or secondary) until the fault is repaired. If no working throttle signal is available at all, the engine drops to its limp home speed and stays there until the code clears.
What triggers a CAT Engine 914 code?
The ECM sets this code when it has been powered for 3 seconds, diagnostic code 168-4 is not active, related 3510 (2131) codes are not active, and the throttle signal has been below the lower diagnostic voltage limit for 1 second.
Common causes of 914
- Damaged, corroded, or loose connectors and wiring in the throttle position sensor circuit
- A problem in the wiring harness between the sensor and the ECM
- A damaged or worn throttle pedal assembly affecting sensor travel
- An intermittent electrical problem in the circuit
- A faulty throttle position sensor that needs to be replaced
- A faulty selector switch input (on machines with a throttle selector)
- A faulty ECM (less common, checked only after wiring and sensor are cleared)
How to troubleshoot CAT Engine 914: first checks
- Inspect all electrical connectors and wiring on the throttle position sensor circuit for corrosion, loose pins, chafing, or damage
- Inspect the throttle pedal assembly itself for physical damage or binding that could affect sensor travel
- Check the throttle position status on the diagnostic service tool while slowly operating the pedal through its full range
- Check the supply voltage at the sensor and confirm it matches the 8.0 ± 0.4 VDC the ECM should be providing
- Check the signal frequency and duty cycle at the sensor, then check the same signal frequency and duty cycle at the ECM to isolate whether the fault is in the sensor, the harness, or the ECM
How the code clears
No separate clearing step is listed beyond repairing the root cause. Once the connectors, wiring, pedal assembly, or sensor are repaired or replaced and the signal returns to a normal range, the ECM should stop logging the code on the next cycle. Note that inputs from a repaired throttle circuit are ignored by the ECM until the keyswitch has been cycled, so a key cycle after the repair is necessary before normal throttle response returns.
Affected models and serial ranges
914 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 fault code 914 mean?
It means the ECM detected a voltage below normal on the throttle position sensor circuit (SPN 91 / FMI 4). The sensor's PWM signal, which tells the ECM the pedal position, is reading outside the expected range.
Will the engine still run with code 914 active?
Yes, but throttle response will be limited. If a second throttle input is installed, the ECM switches to it. If no working throttle signal is available, the engine defaults to a limp home speed and stays there until the fault is repaired.
Can I adjust the throttle position sensor to fix this code?
No. The sensor cannot be adjusted. The pedal assembly's geometry controls the sensor's travel and output range, so a mechanical problem with the pedal assembly itself, not the sensor calibration, is one thing to rule out.
What voltage should the throttle position sensor be getting?
The ECM supplies the sensor with 8.0 ± 0.4 VDC. Checking this supply voltage at the sensor is one of the standard test steps for this code.
Do I need to cycle the key after repairing the wiring or sensor?
Yes. Once the faulty throttle circuit is repaired, the ECM ignores inputs from it until the keyswitch is cycled, so a key off/on cycle is needed before normal throttle control returns.
Is code 914 the same on all CAT engines?
The underlying description and possible causes are consistent across C13, C15, C18, C27, and C32 engines, though exact test steps and dual-throttle behavior can vary by machine and application.