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.
Normal Operation
The PCM sends a signal through circuit 248 (TN/OG) to the speed control switches, which passes through the clockspring. The return signal is sent to the PCM through circuit 133 (BK) and the clockspring. When the brake pedal is applied, the smart junction box (SJB) sends a message to the PCM to deactivate the speed control, if engaged.
The speed control deactivator switch interrupts circuit 535 (LB/RD), removing the voltage signal to the PCM, when the brake pedal is applied firmly and passes the stoplamp switch trip point. This is a redundant signal to the PCM.
Vehicles equipped with a manual transmission have an additional clutch pedal speed control deactivator switch. The clutch pedal speed control deactivator switch, normally closed, supplies a ground signal to the PCM through circuit 1899 (WH). When the clutch pedal is pressed, the clutch pedal speed control deactivator switch moves to the open position, removing the ground signal from the PCM, which deactivates the speed control. Circuit 1205 (BK) supplies ground to the clutch pedal speed control deactivator switch.
This pinpoint test is intended to diagnose the following:
- PCM not configured for speed control
- Speed control switch
- Digital transmission range (TR) sensor alignment (automatic transmission)
- Clutch pedal speed control deactivator switch (manual transmission)
- PCM
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:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.