Possible causes

– Faulty Vehicle Speed Sensor
– Vehicle speed sensor harness or connectors is open or shorted
– Vehicle speed sensor circuit poor electrical connection
– Faulty Engine Control Module (ECM)

When is the code detected?

The signal sent by the vehicle speed sensor to ECM is too high or intermittent.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Speedometer may not work properly
– Transmission shifting problem

P0503 FORD Description

The vehicle speed sensor outputs a 4 pulse signal for every revolution of the rotor shaft, which is rotated by the transmission output shaft via the driven gear. After this signal is converted into a more precise rectangular waveform by the waveform shaping circuit inside the combination meter, it is then transmitted to the Engine Control Module (ECM). The ECM determines the vehicle speed based on the frequency of these pulse signals.

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FORD Technical Service Bulletins for P0503 code