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 C1223: Left Rear Wheel Speed Sensor Input Signal Equals Zero & DTC C1227: Left Rear Excessive Wheel Speed Sensor Variation
- Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK. After performing diagnostic system check, go to next step.
- Turn ignition off. Check left rear wheel speed sensor and wiring harness connector for damage. If sensor and connector are damaged, go to step 16) . If sensor and connector are okay, go to next step.
- Check left rear wheel speed sensor jumper harness and jumper connectors for damage. If harness and connectors are damaged, go to step 15) . If harness and connectors are okay, go to next step.
- Disconnect left rear wheel speed sensor directly at sensor connector. Using DVOM, measure resistance between terminals of left rear wheel speed sensor connector. On "W" body, resistance should be 1030-1180 ohms at 68°F (20°C). On "J" body, Achieva, 1998 Grand Am and Skylark, resistance should be 2100-2400 ohms at 68°F (20°C). On Alero, Cutlass, 1999 Grand Am and Malibu, resistance should be 950-1250 ohms at 68°F (20°C). On all models, if resistance is as specified, go to next step. If resistance is not as specified, go to step 16) .
- Using DVOM, select AC voltage scale. Using DVOM, observe voltage while spinning left rear wheel by hand. If voltage is greater than or equal to 100 millivolts (mV), go to next step. If voltage is less than 100 millivolts (mV), go to step 16) .
- Disconnect EBCM/EBTCM connector. See EBCM/EBTCM LOCATION under REMOVAL & INSTALLATION. Using DVOM, measure resistance between speed sensor signal high circuit and speed sensor signal low circuit of EBCM/EBTCM connector. If resistance is infinite, go to next step. If resistance is not infinite, go to step 8) .
- Check EBCM/EBTCM connector for poor terminal contact, corrosion or damage which could result in short between connector terminals. If connector is faulty, go to step 12) . If connector is okay, go to next step.
- Check wiring circuits between wheel speed sensor and EBCM/EBTCM for damage which could result in short between circuits. If wiring is faulty, go to step 13) . If wiring is okay, go to next step.
- Check wiring connectors between wheel speed sensor and EBCM/EBTCM for damage which could result in short between circuits. If connectors are faulty, go to step 14) . If connectors are okay, go to next step.
- Reconnect EBCM/EBTCM connector. Reconnect left rear wheel speed sensor connector. Install scan tool. Test drive vehicle faster than 15 MPH for at least 30 seconds. Using scan tool, display DTCs. If DTC C1223 or C1227 sets as current, go to next step. If DTC C1223 or C1227 does not set as current, go to step 18) .
- Using scan tool, select DATA LIST. Monitor wheel speed sensor speeds. Slowly accelerate to 40 MPH, and then slowly decelerate to zero MPH. If left rear wheel speed sensor speed is constantly higher than other 3 remaining wheel speed sensor speeds, go to step 16) . If left rear wheel speed sensor speed is not constantly higher than other 3 remaining wheel speed sensor speeds, go to step 17) .
- Replace all faulty terminals or connectors.
- Replace damaged wiring harness causing short between circuits.
- Repair damaged wiring harness connectors causing short between circuits.
- Replace left rear wheel speed sensor jumper harness.
- Replace left rear wheel speed sensor.
- Replace EBCM/EBTCM. See ELECTRONIC BRAKE CONTROL MODULE/ ELECTRONIC BRAKE & TRACTION CONTROL MODULE (EBCM/EBTCM) under REMOVAL & INSTALLATION.
- Malfunction is not currently present. An intermittent may be caused by a poor connection, rubbed through wire insulation, or a broken wire inside insulation. Frequency of malfunction can be determined by using enhanced diagnostic function of scan tool.
If ABS warning indicator only illuminates during moist environmental conditions (i.e. rain, snow, car washes), wheel speed sensor circuitry should be checked for signs of water intrusion. Spray suspected area with a 5 percent saltwater solution (2 teaspoons of salt to 12 ounces of water). Test drive vehicle faster than 15 MPH for at least 30 seconds over various road surfaces (i.e. bumps, turns). If DTC resets, replace suspect harness and/or sensor as necessary.
Check for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wiring connections, or damaged wiring harness. Resistance of wheel speed sensor will increase with increased sensor temperature.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.