DTC 25 Left Front Wheel Speed Sensor Fault

Toothed wheel generates a voltage pulse as it moves past sensor. EBTCM/EBCM uses these pulses to determine wheel speed. EBTCM/EBCM 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 control is needed.

EBTCM/EBCM 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 25 will set if there is a short to ground or battery voltage in circuits No. 830 or 873, or a faulty wheel speed sensor. DTC 25 may set if circuits No. 830 or 873 lose continuity and wheel speed sensor signal is lost while driving. DTC 27 should accompany this DTC on next ignition cycle. If DTCs 25 and 27 are set concurrently, diagnose DTC 27 first.

1. Checks if DTC resets during road test.
2. Use Tech 1 to check for sources of induced electrical noise.
3. Checks for damaged wheel speed sensor circuit shield.
4. Checks for intermittent opens/shorts in wheel speed sensor circuits and cables.
5. Checks for proper resistance in sensor.
6. Checks for a short to battery voltage in either speed sensor circuit wires.
7. Checks for a short between speed sensor circuit wires.
8. Checks for a short to ground in speed sensor input circuit wire. A short with a resistance of less than 2 megohms, though not a hard short, can still cause DTC 21 to set.
9. Checks wiring and connectors for intermittents.

Fig 1: DTC 25 Schematic

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC 25 Flow Chart (1 of 2)

Courtesy of GENERAL MOTORS CORP.

Fig 3: DTC 25 Flow Chart (2 of 2)

Courtesy of GENERAL MOTORS CORP.