DTC 27 - Left Front Wheel Speed Sensor Continuity Fault: Notes

Toothed wheel generates a voltage pulse as it moves past sensor. EBTCM uses these pulses to determine wheel speed. EBTCM uses wheel speed sensor signal to calculate vehicle reference speeds and speed, acceleration and slip values for each wheel. These values are used to determine when anti-lock or traction control is needed. See Figure.

EBTCM will only set one wheel speed sensor DTC at a time, even if multiple faults exist. Detection is prioritized accordingly: LF, RR, LR and RF. Check for additional stored DTCs after making repairs.

DTC 27 will set if there is a short to battery voltage or open in circuits No. 830 or 873, or a faulty wheel speed sensor. Testing for this fault occurs with ignition on and vehicle at rest.

Fig 1: DTC 27 Diagnostic Flow Chart

Courtesy of GENERAL MOTORS CORP.

1. Checks for correct resistance in sensor.
2. Checks for short to battery voltage in either speed sensor circuit wire. Circuit No. 830 should have 5 volts.
3. Checks for an open in both speed sensor circuit wires.
4. Manipulates wiring and connectors to induce an intermittent fault not currently present.
5. Checks if DTC resets at key on. If it does, wheel bearing/speed sensor may be causing fault.
6. Checks if DTC 25 sets during road test.
7. Wheel speed sensor may be causing an intermittent fault. If DTC 27 resets after sensor replacement, EBTCM has an internal fault.