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 C1221: Right Front Wheel Speed Sensor Circuit Open Or Shorted
1998 Buick RivieraSECTION DTC C1221: Right Front Wheel Speed Sensor Circuit Open Or Shorted
- Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK. After performing diagnostic system check, go to next step.
- Check right front wheel speed sensor connector and wiring for damage. Check right front wheel speed sensor for damage or looseness. If sensor, connector or wiring is faulty, go to next step. If sensor, connector and wiring are okay, go to step 4) .
- Repair or replace components as necessary.
- Disconnect right front wheel speed sensor connector directly at sensor. Using DVOM, measure resistance between terminals of wheel speed sensor. If circuit resistance is 850-1350 ohms, go to next step. If circuit resistance is not 850-1350 ohms, go to step 6) .
- Using DVOM, measure resistance between terminal "A" (Black wire) of wheel speed sensor and ground. Also, measure resistance between terminal "B" (White wire) of wheel speed sensor and ground. If resistance is infinite for both measurements, go to step 7) . If resistance is not infinite for both measurements, go to next step.
- Replace right front wheel speed sensor.
- Turn ignition off. Disconnect EBCM/EBTCM connector. Using DVOM, measure resistance between terminal No. 47 (Dark Green wire) of EBCM/EBTCM and ground. If resistance is infinite, go to step 9) . If resistance is not infinite, go to next step.
- Repair short to ground in Dark Green wire between wheel speed sensor and EBCM/EBTCM.
- Using DVOM, measure resistance between terminal No. 29 (Tan wire) of EBCM/EBTCM and ground. If resistance is infinite, go to step 11) . If resistance is not infinite, go to next step.
- Repair short to ground in Tan wire between wheel speed sensor and EBCM/EBTCM.
- Reconnect right front wheel speed sensor connector. Using DVOM, measure resistance between terminals No. 29 (Tan wire) and No. 47 (Dark Green wire) of EBCM/EBTCM. If resistance is 850-1350 ohms, go to step 15) . If resistance is not 850-1350 ohms, go to next step.
- Connect a fused jumper between terminal No. 47 (Dark Green wire) of EBCM/EBTCM and ground. Disconnect right front wheel speed sensor connector. Using DVOM, measure resistance between terminal "B" (White wire) of wheel speed sensor connector (harness side) and ground. If resistance is 0-2 ohms, go to next step. If resistance is not 0-2 ohms, go to step 14) .
- Repair open or high resistance in Tan wire between wheel speed sensor and EBCM/EBTCM.
- Repair open or high resistance in Dark Green wire between wheel speed sensor and EBCM/EBTCM.
- Turn ignition to start. Using DVOM set on DC scale, measure voltage between terminal No. 47 (Dark Green wire) of EBCM/EBTCM and ground. If voltage is greater than one volt, go to next step. If voltage is less than one volt, go to step 17) .
- Repair short to voltage in Dark Green wire between wheel speed sensor and EBCM/EBTCM.
- Using DVOM set on DC scale, measure voltage between terminal No. 29 (Tan wire) of EBCM/EBTCM and ground. If voltage is greater than 1 volt, go to next step. If voltage is less than 1 volt, go to step 19) .
- Repair short to voltage in Tan wire between wheel speed sensor and EBCM/EBTCM.
- Replace EBCM/EBTCM.
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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.