CAT Engine 913 Fault Code: Throttle Position Sensor : Voltage Above Normal
Also called Accelerator Pedal Position #1 : Voltage Above Normal, Throttle Position Sensor - Voltage Above Normal, Throttle Position Sensor voltage above normal, Throttle Position Sensor: Voltage Above Normal, Throttle Position Sensor:Voltage Above Normal
Throttle Position Sensor : Voltage Above Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Code 913 (SPN 91 / FMI 3) means the ECM sees a throttle position sensor signal voltage that is above the normal operating range. It affects C13, C15, C18, C27, and C32 engines. The engine will use a backup throttle if one is installed, or drop to a limp home speed until the fault is fixed.
Medium severity. The engine does not shut down, but it will limit power by switching to a secondary throttle or forcing a limp home speed. This limits productivity and can be a safety concern in machines needing responsive throttle control, so it should be diagnosed promptly rather than run indefinitely.
What does CAT Engine error code 913 mean?
Code 913 is set when the Electronic Control Module (ECM) detects a voltage above the normal range on the circuit for the throttle position sensor. This sensor is mounted to the pedal assembly and sends the ECM a PWM signal that tells it how far the operator has pressed the throttle pedal.
The sensor produces a minimum duty cycle when the pedal is released, which the ECM reads as 0 percent throttle, and a maximum duty cycle when the pedal is fully depressed, read as 100 percent throttle. The sensor itself cannot be adjusted; its range is set entirely by the geometry of the pedal assembly.
The ECM supplies the sensor with 8.0 ± 0.4 VDC and also provides a separate digital return. The ECM also runs an automatic calibration function that adjusts the duty cycle range it expects at powerup if the sensor's signal exceeds the initial assumed range. When the incoming signal voltage climbs above what the ECM considers normal for this circuit, code 913 is triggered.
What triggers a CAT Engine 913 code?
The ECM sets this code when it has been powered for 3 seconds, diagnostic code 168-4 is not active, and no 3509 (262) codes are active, along with the upper diagnostic limit for the sensor signal being exceeded for 1 second. If a warning lamp is equipped, it will illuminate and the code will be logged.
Common causes of 913
- Damaged, corroded, or loose connectors and/or wiring in the throttle position sensor circuit
- A general problem within the wiring harness carrying the sensor signal
- A damaged or worn throttle pedal assembly affecting sensor travel and output range
- An intermittent electrical problem in the circuit that comes and goes
- A faulty throttle position sensor that needs to be replaced
- A faulty selector switch input tied to the throttle circuit
- A faulty ECM that needs to be replaced
How to troubleshoot CAT Engine 913: first checks
- Visually inspect all connectors and wiring related to the throttle position sensor for damage, corrosion, or loose pins
- Inspect the throttle pedal assembly itself for physical damage or binding that could affect sensor travel
- Use a diagnostic service tool to check the live status of Throttle Position and watch it as the pedal is worked through its full travel
- Check the supply voltage at the sensor and confirm it reads within the expected 8.0 ± 0.4 VDC range
- Check the signal frequency and duty cycle at the sensor, then compare it against the signal frequency and duty cycle read at the ECM to isolate a harness issue from a sensor issue
How the code clears
No separate clearing step is listed beyond repairing the underlying cause. Once the wiring, pedal assembly, sensor, or ECM issue is corrected and the signal stays within normal range, the code should stop being active. Note that inputs from a previously faulty throttle are ignored by the ECM until the keyswitch is cycled after the repair, so cycle the key off and on once the fix is complete.
Affected models and serial ranges
913 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 913 mean?
It means the ECM has detected a voltage above the normal range on the throttle position sensor circuit, which carries the PWM signal telling the engine how far the throttle pedal is pressed.
Will the engine still run with code 913 active?
Yes. If a secondary throttle is installed, the engine will use it until the primary is repaired. If no functional throttle is available, the engine defaults to a limp home speed and stays there while the code is active.
Can I adjust the throttle position sensor to fix this code?
No. The throttle position sensor cannot be adjusted. Its output range is set by the geometry of the pedal assembly, so if the assembly is worn or damaged it needs to be repaired or replaced rather than adjusted.
What voltage should the throttle position sensor be getting?
The ECM supplies the sensor with 8.0 ± 0.4 VDC along with a separate digital return. Checking this supply voltage at the sensor connector is one of the first diagnostic steps.
Why does the engine stay at a fixed speed after this code sets?
Once code 913 is active, the ECM ignores all inputs from the faulty throttle circuit and holds the engine at the limp home speed, or lets it stay below that speed if it was already lower, until the fault is repaired.
Do I need to cycle the key after repairing the throttle sensor issue?
Yes. Even after the fault is fixed, the ECM will continue to ignore inputs from the repaired throttle circuit until the keyswitch has been cycled.
Which CAT engines can show code 913?
This code applies to the C13, C15, C18, C27, and C32 engine models.