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 C1237: Left Rear Wheel Speed Sensor Signal Missing
1998 Buick RivieraSECTION DTC C1237: Left Rear Wheel Speed Sensor Signal Missing
- Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK. After performing diagnostic system check, go to next step.
- Check left rear wheel speed sensor connector and wiring for damage. Check left rear wheel speed sensor for damage or looseness. If sensor, connector or wiring is faulty, go to step 7) . If sensor, connector and wiring are okay, go to next step.
- Disconnect left rear 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 8) .
- With DVOM still connected, select millivolt (mV) AC scale. Spin wheel by hand as fast as possible while monitoring AC output. If voltage is greater than 100 mV, go to next step. If voltage is less than 100 mV, go to step 8) .
- Disconnect EBCM/EBTCM connector. Using DVOM, measure resistance between terminals No. 46 (Black wire) and No. 28 (Red wire) of EBCM/EBTCM. If resistance is infinite, go to next step. If resistance is not infinite, go to step 9) .
- Reconnect all connectors. Test drive vehicle greater than 15 MPH for at least 30 seconds while monitoring scan tool for ABS/TCS DTCs. If DTC C1237 resets, go to step 10) . If DTC C1237 does not reset, see INTERMITTENTS & POOR CONNECTIONS under DIAGNOSIS & TESTING.
- Repair or replace damaged components as necessary. Test drive vehicle greater than 15 MPH while monitoring scan tool for DTCs. If DTC C1237 resets, go to step 3) . If DTC C1237 does not reset, see INTERMITTENTS & POOR CONNECTIONS under DIAGNOSIS & TESTING.
- Replace left rear wheel speed sensor. After repairs, go to step 11) .
- Repair short between Red wire and Black wire. After repairs, go to step 11) .
- Replace EBCM/EBTCM. After repairs, go to next step.
- Test drive vehicle greater than 15 MPH for at least 30 seconds while monitoring scan tool for ABS/TCS DTCs. If DTC C1237 resets, go to step 2) . If DTC C1237 does not reset, see INTERMITTENTS & POOR CONNECTIONS under DIAGNOSIS & TESTING.
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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.