1998 ram 1500 van speedo issues

sirtokesalot · Jul 6, 2017

i have been trying to figure out why the speedo is not working in my grandmothers van she has a 1998 dodge ram 1500 conversion van. it had a check engine code for the speed sensor we changed both the sensor in the tail of the transmission and the sensor on the rear diff. speedo still only works intermittently it never shows the actual mph and is moving around alot like say if im really doing 45 the speedo is showing around 20 to 40 mph bouncing around in that range it sometimes cuts out completely as well. the speedo will also cut out if the brake is applied. the abs light and brake lights are not lit. the check engine light is still coming on but my code reader claims no codes in the computer when i attempt to read it. i followed the wires from the rear speed sensor up to this computer module near the brake lines i think it may be an abs module and verified the wires are not broken between the sensor and this module using a volt meter but i do not know what path the wire takes after leaving that module as i cannot locate any kind of pinout of that module anywhere.does anyone have acces to wiring diagrams for the 1998 dodge ram 1500? im looking for a schismatic for the abs rwal module with pinout of the connector if possible. im trying to figure out what wires would have to be jumped to allow the speed signal to bypass the abs module and go strait to the cluster.

sirtokesalot · Jul 6, 2017

ok updates ive found pinouts but not sure what wire to jump into the pcm. there is 2 wires from the rear sensor coming to the abs module a + signal and a - signal. the abs module then sends out a singal speed signal to the pcm but is that signal + or - the wiring diagrams are not telling me this.

dudeman2009 · Jul 6, 2017

You cant bypass the ABS module. Dodge is a whole other beast from ford or Chevy, imo its better the way Dodge does it.

The signal coming from the speed sensor isn't a standard signal, simply put its an AC signal that varies with speed that the ABS module interprets and sends a completely different signal to the PCM. If you jump the wires, you risk destroying a section of the PCM. I'm not sure what type of signal the PCM receives from the ABS module, it could be DC, AC or PWM. No matter what it is, its a data line, no significant amount of power will flow over it, you'll want to check the line at both connectors to make sure it hasn't pulled out.

If you're truck has the digital odometer, perform the cluster self test. Key off hold the odometer button, turn key to run but do not start the engine, hold the odometer button until the word Check displays on the odometer, then let go and watch all the gauges.

sirtokesalot · Jul 7, 2017

dudeman2009 said:
You cant bypass the ABS module. Dodge is a whole other beast from ford or Chevy, imo its better the way Dodge does it.

The signal coming from the speed sensor isn't a standard signal, simply put its an AC signal that varies with speed that the ABS module interprets and sends a completely different signal to the PCM. If you jump the wires, you risk destroying a section of the PCM. I'm not sure what type of signal the PCM receives from the ABS module, it could be DC, AC or PWM. No matter what it is, its a data line, no significant amount of power will flow over it, you'll want to check the line at both connectors to make sure it hasn't pulled out.

If you're truck has the digital odometer, perform the cluster self test. Key off hold the odometer button, turn key to run but do not start the engine, hold the odometer button until the word Check displays on the odometer, then let go and watch all the gauges.

check dont jump the signal. i did the self test and the speedo moved up to 20 then 60 and finally at max speed before going back down to 0 i think the cluster is ok. what would you say i should check next?

sirtokesalot · Jul 8, 2017

would there be any danger of using the speedo cluster from our 1999 dodge van in the 1998 dodge van to verify if the cluster is bad or not?

dudeman2009 · Jul 9, 2017

You can swap the clusters all you want. Seeing as the issue seems to be intermittent and random, you're looking at checking out all the wires to and from the sensors to the control modules.

1998 ram 1500 van speedo issues

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