DTC 28 Wheel Speed Sensor Frequency Error: Notes

Toothed wheel generates a voltage pulse as it moves past sensor. EBCM uses these pulses to determine wheel speed. Amount of voltage generated in each pulse depends on wheel speed and air gap between sensor and toothed wheel.

28 will set if EBCM cannot specifically identify which wheel speed sensor is causing frequency error. If EBCM can identify specific wheel speed sensor causing trouble, for that sensor ( 21, 25, 31, or 35) will be set instead of 28.

1. Checks wiring and connectors. Performing this step is critical as wiring or connector malfunction is most likely cause for this to set.
2. Monitors electrical system for noise picked up by wheel speed sensor circuits.
3. Monitors wheel speed sensors while vehicle is operating. If Tech 1 auto-trigger snapshot mode triggers, wheel speed sensor or wiring and/or connectors are going intermittent during road test.
4. Checks resistance of wheel speed sensor. 5a) Replaces rear wheel speed sensor as most likely cause of intermittent. 5b) Replaces front wheel speed sensor as most likely cause of intermittent.
5. Ensures fault is not due to suspected wheel speed sensor.
6. Checks for short to ground in wheel speed sensor circuit. A short with a resistance of less than 2 megohms, though not a direct short, may set 28.
7. Ensures is not due to electro-magnetic interference.