DTC 28 Wheel Speed Sensor Frequency Error: Notes

Toothed wheel generates a voltage pulse as it moves past sensor. EBTCM 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. ANTI-LOCK and TRACTION CONTROL warning indicators will turn on and DTC 28 will set if EBTCM cannot identify which wheel speed sensor is causing frequency error problem. If EBTCM can determine wheel speed sensor causing error problem, sensor DTC associated with that sensor (DTC 21, 25, 31 or 35) will be set instead of DTC 28.

1. Checks wiring and connections.
2. Uses Tech 1 scan tester to monitor vehicle electrical/electronic system noise being picked up by wheel speed sensor circuits.
3. Uses Tech 1 scan tester to monitor wheel speed sensor during vehicle operation. If Tech 1 auto trigger snapshot triggers, speed sensor, wiring and/or connectors are intermittent during road test.
4. Checks for proper sensor resistance.
5. Probable cause for intermittent is a defective wheel speed sensor. Replace sensor. If DTC resets, replace EBTCM.
6. Checks for short to ground in wheel speed sensor input wire. Short to ground may be a "hard" short to ground or a resistive (partial) short. A short with resistance less than 2 megohms, though not a "hard" short, can still cause a DTC 28 to set.