Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC 21 - App No. 1 Circuit High (Models With Pcm): Notes
The Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator position. There are 3 sensors located within the APP module that are scaled differently. DTC 21 will set when voltage is greater than 4.75 volts for 2 seconds on APP No. 1 sensor. PCM will default to the input from the APP No. 1 sensor being ignored. A current and history DTC will set but will not turn on the SERVICE THROTTLE SOON light. The throttle will operate normally as long as there is only one sensor malfunctioning.
If 2 different APP sensors have a malfunction, the SERVICE THROTTLE SOON light will light and the PCM will limit power. If 3 APP sensors malfunction, the SERVICE THROTTLE SOON light will light and the PCM will only allow the engine to operate at idle.
- This step determines if DTC 21 is the result of a hard failure or an intermittent condition.
- This step checks the PCM and wiring.
- This step checks for an open in the ground circuit.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.