Vehicle Speed Sensor- (question!)

I have a friend who owns a 1996 Rodeo, he has been having trouble with no speedo (analog speedo not working)....and has SES light on (PO502- "Vehicle Speed Sensor- Low input")

1) I have replaced the vehicle speed sensor (rear of tranny) due to a "repair" shop exclaiming that to be the problem.

2) After replacing part- (I couldn't erase code since I do not own a scan tool), I noticed no change to speedo as well!! -still inop!!!

3) Can anyone Please tell me the correct diag. path for repairing this code?.... Is the correct sensor to be replaced the one on the rear end: "Wheel speed sensor"? Would this wheel speed sensor have anything to do with speedo operation or is it just reference to RWAL?

Any info will be GREATLY appreciated!

Thanks!


-Nick- :)

Just a thought that came to my mind: Are you sure you got the right thing? "Wheel Speed Sensor" kinda sounds like an anti-lock brake component.

...Yeah- actually I just checked a wire diagram and flow chart at a local library. The speedo circuit is powered by 12v by the "Meter"/30 amp fuse-----> which is sent to the VSS (vehicle speed sensor which is in tail end of trans) and also works (spliced in conjunction) to PCM/VCM (main computer) which I believe sends out a 9v reference signal----> As far as components: It can be either a VSS (sensor) or PCM (power control module) or a fuse (30 amp/ 'Meter'). BUT, It can also be an open or shorted wire somewhere (maybe unlikely) or at a very least (even a bad cluster guage-not registering the speedo!)

...I do not have a scan tool to check voltage or sensor operation (MPH/ vehicle speed) I am thinking (and leaning) towards the 'main' PC (VCM)

ANYONE ELSE RAN INTO SIMILIAR PROBLEM?

* What I can also try is giving the sensor (VSS) a "known good ground"--> Splice a wire into blk sensor wire and clamping it on the chassis or something since I remember checking the diagram and seeing that that wire (blk wire off sensor) is a ground wire and goes directly to ground! [It is not grounded at the PCM per say!]-maybe I have an 'Open' ground wire!]


Thanks again!


-Nick- :)

BTW: I believe the other sensor (WSS/ wheel speed sensor) which is located on the rear end is for ABS brakes (RWAL) as far as reference ONLY. (telling the ABS module/PC how fast rear wheel is spinning)- I don't think that has anything to do with vehicle speed as far as speedo is concerned!



-Nick- :)

apparently there is a speed sensor which should be behind the dash/speedometer..ETC i know since in the last 2 cars i had they were behind the dash.. it should be a small plastic square box with a hole in the middle & a cable(i don't know what u call it) that goes into that sensor to measure the rotation of the engine. if that is defective u get no speedometer reading.

-scott