Auto Repair Q&A



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I have a 1995 ford f-350 dully with a 460 motor. I went to go to work today and now my speedometeris not working,it is shifting real hard, a b s light is on and the overdrive on -off light is blinking. I have replaced the speed sensor mounted on rear end

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1. Check for the presence of an illuminated ABS light. If the ABS light is on, perform self-test of the ABS module. If the ABS is a 2-wheel rear only system, a DSS circuit code would be a 9. If the vehicle is equipped with 4 Wheel Antilock Brake System (4WABS), the ABS module would set code C1229 or C1230 related to the DSS or circuit

2. If a DSS code has been set by the ABS module, check the circuits of the DSS running between the sensor and the ABS module or speedometer head for an open or short to ground in the harness.

3. If there is no ABS light illumination suggesting a potential DSS circuit problem, check the alternating current input voltage to the Programmable Speedometer Odometer Module (PSOM) measuring between the Light Green/Black (LG/BK) wire and the Red/Pink (R/PK) wire on its connection. The sensor should produce a signal of 1.25 volts or more at 30 MPH.

4. Check the PSOM power and ground circuits.

5. If the VSS input to the PSOM is OK as well as the power and grounds, replace the PSOM.