Circuit Description

Wheel speed sensors on each wheel deliver an input signal to brake Electronic Control Unit (ECU) for the Anti-Lock Brake System (ABS). Brake ECU converts input signals from wheel speed sensors to a 4-pulse input signal to the instrument cluster. Instrument cluster then converts 4-pulse input signal to a rectangular waveform and then sends vehicle speed signal to Engine Control Module (ECM). DTC is set if there is no vehicle speed signal to ECM while vehicle is being driven. Brake ECU may also be referred to as ABS ECU. Possible causes are:

• Vehicle speed circuit is open or shorted between instrument cluster and ECM.
• Defective instrument cluster.
• Defective brake ECU.
• Defective ECM.