speedometer Odometer not working? 96 lumina


ladagosta
04-15-2010, 10:29 AM
I need to locate that PCM.. or figure why my speedometer is not recording milage or speed... trip isnt working either, if it helps..
I do hear a noise that sounds like it should be registering but then again with everything behind the cluster it is hard to tell what actually is making the noise like a plastic spinning wheel back there..
i took the dash appart and nothing appears to be off behind that.. all connected and no broken, cracked or rusty wires..

i did pull every last one of my fuses..in all 3 panels.. found something interesting.. i have a wire running up into the DS engine fuse compartment which has a 30 amp large fuse which was snaped in half.. not the metal that was still in tact..?STRANGE? but the plastic casing was snapped I replaced it anyway to be on the safe side .. does not appear to have changed anything on the way it functions.. it is not labeled so i have no clue what it is for.. ..LOL

i am gonna make a run to the u pull it later today so i would like to know where to locate it so i can pull one and test it out.. thank you for all you help...thnx in advance LAD

kevinb70
04-15-2010, 01:50 PM
ECM located in ur other thread.

as far as speedo, this isnt the old style speedo where you got the "wire within a tube" that mechanically drove the speedometer gauge... the VSS is in the transaxle and that signal goes directly to the ECM where its used for powertrain management functions... computer also delivers a signal to the instrument cluster to control the speedometer gauge. our speedo is an electrically driven gauge

ladagosta
05-02-2010, 08:53 PM
ok Kevin forgive me but what should i be replacing I never went to get the cluster since I am not positive that is what is needed... I did get the overheating issue resolved will post resolution in correct post.. but still have the speedo issue.. plus 2 others popped up but not a mystery I will post them with the solution in cse any one has issues with them,..

kevinb70
05-02-2010, 10:41 PM
here's my amateur diagnosis.

ok, i know the transmission needs input from the VSS via the PCM in order to shift correctly. you haven't mentioned a shifting issue, so im going with the VSS is ok, and it's connection to the PCM.

so then im seeing only thing left is the connection from PCM to the instrument cluster, and the speedometer needle/coil itself (whose needle works exactly like the needle type multimeters)

scantool should be able to read vehicle speed via OBD-II link. does it show 0mph or correct vehicle speed?

since the PCM isn't throwing codes for not detecting vehicle speed, i think problem is in the display

does the odometer/tripmeter work?

ladagosta
05-03-2010, 12:33 PM
here's my amateur diagnosis.

ok, i know the transmission needs input from the VSS via the PCM in order to shift correctly. you haven't mentioned a shifting issue, so im going with the VSS is ok, and it's connection to the PCM.

so then im seeing only thing left is the connection from PCM to the instrument cluster, and the speedometer needle/coil itself (whose needle works exactly like the needle type multimeters)

scantool should be able to read vehicle speed via OBD-II link. does it show 0mph or correct vehicle speed?

since the PCM isn't throwing codes for not detecting vehicle speed, i think problem is in the display

does the odometer/tripmeter work?


it shows 0 mph
nothing is working on trip miles or speedo.

ladagosta
05-03-2010, 07:54 PM
okay well i replaced the sensors on the instrument panel obviously it is the panel itself where the problem is .. or it is something completely elsewhere.. I am running out of places to check.. could something be disconnected somewhere? I just cant seem to pin point this for resolve.. the contacts and connections all appear to be fine.. the trip and odometer and speedometer will not work no matter what i have done to try to resolve.. athough I did put a new trip and odemeter sensor on today suprised me when i turned the key on the speedo went to 70 mph and stopped there like there was s signal but then i spun it back to 0 and took it for a test run adn nothing happened.. but when i put it in and turned it on something registered.. but then nothing after that... ?? what gives here.?

Blue Bowtie
05-04-2010, 10:28 PM
The PCM conditions the signal from the VSS then sends a signal to the speedo, a separate signal to the cruise, and uses the VSS data to drive the transmission solenoids. If the trans is operating normally the VSS is probably working. Same with the cruise.

The speedo uses the output pulses operate the speedo display (stepper motor) and this stepper also drives the odometer wheels (the trip odometer is geared to the main odometer). The faint clicking you are hearing may be the stepper motor trying to follow the PCM signals. Either the speedo head is mechanically worn or the PCM output is weak or scrambled to the point where it won't signal the speedo correctly. However, the speedo head also uses a pulse counter/divider circuit to further condition the PCM signal and the power to drive the stepper is actually from a separate source from the PCM. The PCM only provides the low level signal.

Since you've evidently replaced the speedo head it may be time to look at the PCM wiring under the coolant recovery tank.

ladagosta
05-05-2010, 02:52 PM
The PCM conditions the signal from the VSS then sends a signal to the speedo, a separate signal to the cruise, and uses the VSS data to drive the transmission solenoids. If the trans is operating normally the VSS is probably working. Same with the cruise.

The speedo uses the output pulses operate the speedo display (stepper motor) and this stepper also drives the odometer wheels (the trip odometer is geared to the main odometer). The faint clicking you are hearing may be the stepper motor trying to follow the PCM signals. Either the speedo head is mechanically worn or the PCM output is weak or scrambled to the point where it won't signal the speedo correctly. However, the speedo head also uses a pulse counter/divider circuit to further condition the PCM signal and the power to drive the stepper is actually from a separate source from the PCM. The PCM only provides the low level signal.

Since you've evidently replaced the speedo head it may be time to look at the PCM wiring under the coolant recovery tank.

thank you BB,, I will look into the PCM.. not likely to be the circuit board that the speedo head connects to?

everything else appears to be working fine on the circuit board outside of the odometer, trip and speedo.. all of them are dead still..PCM is the next thing I am taking a week away from this mess, break time, before my brain fries...

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