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.
Code 21 Or 23 (Speed Sensor Circuit)
Code 21 sets if the cruise control ECU does not receive a speed signal from the instrument cluster. Code 23 sets if speed sensor circuit is open intermittently, or if vehicle speed decreases to at least 10 MPH (16 KM/H) less than set speed.
- Check if cruise control ECU is receiving input signal from speed sensor (instrument cluster). See INPUT SIGNAL CIRCUITS under CIRCUIT TESTING. If input signal circuit is not okay, go to next step. If input signal circuit is okay:
- CODE - Replace cruise control ECU
- NO CODE - Perform next procedure listed in DIAGNOSIS BY SYMPTOM table.
- Check if speedometer operates. Repair speedometer if it does not operate. See INSTRUMENT PANEL article in the ACCESSORIES/SAFETY EQUIPMENT section. If speedometer operates, check for faulty circuit between instrument cluster and cruise control ECU. If circuit is okay, replace cruise control ECU.
Use the Manual With the Right Hardware
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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.