98 dodge 2500 4x4 speedometer ONLY not working

Asked by Feb 26, 2015 at 04:47 PM about the 1998 Dodge Ram 2500 Laramie SLT 4WD Standard Cab LB

Question type: Maintenance & Repair

so far i changed the abs sensor at
the differential and the output speed
at the transmission. The abs light its
not on ONLY speedometer not
working. I would appreciate any
sugestions thank you

3 Answers


hi here is an explanation of how the system works I tried to find a wiring diagram but did not find it ...// will keep looking and post it when I find it The speedometer gives an indication of the current vehicle speed. The instrument cluster circuitry controls the gauge pointer position. The instrument cluster circuitry calculates the proper gauge pointer position based upon vehicle speed messages received from the Powertrain Control Module (PCM) on the Chrysler Collision Detection (CCD) data bus. The PCM uses a speed pulse input received from the Controller Anti- lock Brake (CAB) and internal programming to decide what vehicle speed and distance messages are required. The PCM then sends the proper messages to the instrument cluster circuitry on the CCD data bus. The CAB uses an input from the rear wheel speed sensor and internal programming, which includes a programmable pinion factor to compensate for different axle gear ratios and tire sizes, to determine what speed pulse output is required. The CAB then sends the proper speed pulse to the PCM on a hard-wired circuit. The rear wheel speed sensor is excited by an exciter ring on the differential case within the rear axle housing. Incorrect tire size, incorrect axle ratio, an incorrect pinion factor, a faulty or improperly installed rear wheel speed sensor, a faulty rear axle exciter ring, or a faulty CAB can each result in inaccurate speedometer readings. For diagnosis of the speedometer inputs, a DRB scan tool and the proper Diagnostic Procedures manual are recommended. Refer to Brakes for more information on the CAB, the rear wheel speed sensor and the rear axle exciter ring. Refer to Fuel Systems for more information on the PCM.

I did forget to mention that the airbag light is on not the srs just airbag. Could that be linked to the speedometer not working?


I don't know much about Dodge trucks but worse case scenario there is speedometer apps available for your smartphone I have DIGI HUD it works great with many features

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