96 Chevy Cheyenne speedometer stopped working
emiracleworker1
03-13-2012, 06:49 PM
I have a 96 Chevy Cheyenne 3500 4x4, 5 speed and the speedometer has quit working. I was tying up some loose wires under it the other day and "possibly" could have caused the problem. I've never driven the truck prior to today so no clue if it worked before. It could be the VSS, but I am curious if there are any troubleshooting tips? ie. what wires (colors) should I be looking for? It appears there's only 2 coming off the VSS that loop over the transfer case into a loom on the passenger side. I'd imagine one wire is a power supply and the other is a return wire with resistance based on the vehicle speed? If I knew where to look under the hood or dash, I could test continuity and determine if there's a break in either wire... since laying under the truck and staring at them isn't getting me anywhere. Also, are the sensors on the front brakes at all connected to the speedometer? Is there the chance of something stupid like a fuse? Everything else in the dash and on the truck is working fine except the radio since there isn't one. Thanks for any help in advance!
Schurkey
03-14-2012, 10:24 PM
Everything else in the dash and on the truck is working fine
When the speedo quit working on my '88, the odometer, cruise control, and ABS all quit with the speedo; and all came back when the speedo began working again.
The fault was the electronic circuitry in the instrument cluster, not the speedo itself; or the wiring from the speed sensor.
Since you aren't having problems with the odometer, cruise, or ABS, I'd suspect a defective speedometer gauge.
This is based on troubleshooting the '88; and perhaps the '96 is wired differently.
When the speedo quit working on my '88, the odometer, cruise control, and ABS all quit with the speedo; and all came back when the speedo began working again.
The fault was the electronic circuitry in the instrument cluster, not the speedo itself; or the wiring from the speed sensor.
Since you aren't having problems with the odometer, cruise, or ABS, I'd suspect a defective speedometer gauge.
This is based on troubleshooting the '88; and perhaps the '96 is wired differently.
emiracleworker1
03-16-2012, 02:18 PM
I should have clarified... the odometer is not working either. I'm pretty sure the 88 and 96 are wired differently. I have a 92 that has a completely different dash. I am almost positive all my reaching around and moving wires did something. The truck had a loom of wires on the passenger side of the transfer case that were dangling nearly to the ground. I manipulated them around until I could get a zip-tie around them. I also did some similar fumbling under the hood. My problem is that I have no clue which wires to start tracing.... obviously start at the VSS and see if there's a signal to/from it then test at the instrument cluster and start working backward from there. I just don't know which wires (color combinations) to be looking for and if they change color in/out of the controller (or if there's a controller). I do have the "service engine soon" light on, which should help me figure things out BUT the code reader can't detect the protocol. I had to replace the cig lighter fuse just to get the code reader to power up, but then it just sits there and never detects the protocol to pull the code. Any thoughts?
j cAT
03-16-2012, 02:57 PM
no speedo no odometer thats what happens when the VSS on the tranny is broken.
on the driverside near the very rear you will see a connector and maybe the wires going to it / maybe not ! any way this is the VSS.
a stud holds the sensor in position . an O ring seals the transmission from leaking. could be the wire ripped off.
this is for a nv3500/4500 5speed .
on the driverside near the very rear you will see a connector and maybe the wires going to it / maybe not ! any way this is the VSS.
a stud holds the sensor in position . an O ring seals the transmission from leaking. could be the wire ripped off.
this is for a nv3500/4500 5speed .
emiracleworker1
03-16-2012, 04:29 PM
Thanks... the wires are still connected to it, just seem to be a little "tight" as they go over the transfer case which is what worried me. I'll just go ahead and replace the VSS and go from there. Do you know if this specific model ties the brake sensor into the speedo?... as explained before, the vehicle had been in storage for many years and I wasn't the prior driver. I've noticed the passenger front brake rotor is totally screwed. The brakes have worn into it so badly that portions of the fins are actually missing! I'm shocked it didn't destroy the caliper, but again curious if I'd be chasing my tail until I replaced the brakes (and possibly the sensor at the wheel).
j cAT
03-16-2012, 06:03 PM
Thanks... the wires are still connected to it, just seem to be a little "tight" as they go over the transfer case which is what worried me. I'll just go ahead and replace the VSS and go from there. Do you know if this specific model ties the brake sensor into the speedo?... as explained before, the vehicle had been in storage for many years and I wasn't the prior driver. I've noticed the passenger front brake rotor is totally screwed. The brakes have worn into it so badly that portions of the fins are actually missing! I'm shocked it didn't destroy the caliper, but again curious if I'd be chasing my tail until I replaced the brakes (and possibly the sensor at the wheel).
I would follow those wires back and check that they have not worn into the case shorting out the signal.
with the ABS the signals from the VSS and the front hubs need be working or the ABS is off.
If you need any brake parts for cheap go to the scrap yard and see if you can get all you need. lookup parts and vehicle compatibility then load up.
I would follow those wires back and check that they have not worn into the case shorting out the signal.
with the ABS the signals from the VSS and the front hubs need be working or the ABS is off.
If you need any brake parts for cheap go to the scrap yard and see if you can get all you need. lookup parts and vehicle compatibility then load up.
emiracleworker1
03-16-2012, 06:23 PM
Again, Thanks... I think that is what was throwing me a bit. I had read somewhere that part of the signal for the speedo runs through the ABS. The ABS is working fine with exception to significant wear on one of the rotors... and I'm not kidding when I say that some of the fins inside the rotor are totally gone and parts of the rotor are missing... you can feel them operating as if they were compensating for those missing fins. So, answering my question if I understand you correctly- If there was damage to that sensor on the brake and/or the VSS sensor was defective, then my ABS would be OFF? I guess I am thrown off a bit in assuming that if I had a bad wire or something grounding out, the ABS would still be OFF (under the assumption that the vss, speedo and brake sensor could not communicate) and the ABS seems to be fine.
All that said, I guess I'm asking for the extra effort in putting it into idiot's terms! Also, my statement on the OBD II reader not being able to detect the protocol.... any insight as to why it's powering up, but not able to read anyting?... very possible that pulling a code would answer my question of whether to be looking at wires or just replacing the VSS.
All that said, I guess I'm asking for the extra effort in putting it into idiot's terms! Also, my statement on the OBD II reader not being able to detect the protocol.... any insight as to why it's powering up, but not able to read anyting?... very possible that pulling a code would answer my question of whether to be looking at wires or just replacing the VSS.
777stickman
03-16-2012, 07:23 PM
This from my '98 C/K service manual. Your '96 may be different.
2 wires from the VSS (LT GRN/BLK & PPL/WHT) go directly to the VCM pins 29 & 30 of the BLUE labeled connector (C1). Pin 15 of this same connector sends a signal to the EBCM (anti-lock) module.
The VCM sends an output signal to the speedo on pin 4 (DK GRN) of the BLACK labeled connector (C4).
If you don't have an amber (anti-lock) light glowing on the I/P, I would think the VSS is working OK.
Sounds like you have a lot of issues with this truck. Maybe a subscription at this link will make it easier for you.
http://alldatadiy.com/
2 wires from the VSS (LT GRN/BLK & PPL/WHT) go directly to the VCM pins 29 & 30 of the BLUE labeled connector (C1). Pin 15 of this same connector sends a signal to the EBCM (anti-lock) module.
The VCM sends an output signal to the speedo on pin 4 (DK GRN) of the BLACK labeled connector (C4).
If you don't have an amber (anti-lock) light glowing on the I/P, I would think the VSS is working OK.
Sounds like you have a lot of issues with this truck. Maybe a subscription at this link will make it easier for you.
http://alldatadiy.com/
emiracleworker1
03-16-2012, 07:58 PM
Thanks... that's what I was hoping to come across. It's one thing to follow the wires while laying under it, but another thing to guess what connector they went into and what signal is coming out of a different connector! I could probe wires for a week and never never know what I'm looking for. I only have a book for the 1999 and up, which is a whole different ball game.
Believe it or not, I'm not having very many issues with the truck considering it sat in a garage full of critters for almost 10 years! I towed it home, put fresh gas in and it cranked right up... a tune up later and it's running perfect other than the brake rotor surprise, the speedo and no ability to pull whatever code is lighting up "service engine soon".
Believe it or not, I'm not having very many issues with the truck considering it sat in a garage full of critters for almost 10 years! I towed it home, put fresh gas in and it cranked right up... a tune up later and it's running perfect other than the brake rotor surprise, the speedo and no ability to pull whatever code is lighting up "service engine soon".
777stickman
03-16-2012, 11:27 PM
In the I/P fuse panel, fuse #7 25a "AUX PWR" is for the DLC.
emiracleworker1
03-17-2012, 08:27 AM
I found that fuse... at first the code reader wouldn't even power up. With the fuse replaced, it powers up fine but never detects the truck's computer.
j cAT
03-17-2012, 09:07 AM
with no speed input the ABS is off. thats a certainty...also the abs will appear to be just fine because it is totally off. you will not have any braking effort problems. the brakes will lockup and you will stop.
if the speed sensor has an erratic signal, then you can loose you braking effort and that is a scary experience.
you will not get any ABS codes because you need a scan tool that can pull this from the computer. this is very expensive to own for the DIY types.
engine codes is about all you can get. drivetrain/abs/body dtc NO!
if the speed sensor has an erratic signal, then you can loose you braking effort and that is a scary experience.
you will not get any ABS codes because you need a scan tool that can pull this from the computer. this is very expensive to own for the DIY types.
engine codes is about all you can get. drivetrain/abs/body dtc NO!
emiracleworker1
03-19-2012, 09:49 AM
Sounds good... thanks! I'm going to try and knock out the brakes today before attempting to troubleshoot the speedo... which are the most involved I've ever seen! Have to pull the 4 bolts on the back, looks like pull the spindle nut, then remove the hub just to free up the rotor! What was so wrong with a standard fall-off type rotor? Can't see figuring out how fast I'm going if I can't stop the truck! I'll post what I find "if" this small town parts store can get the VSS... thinking I just start there and if it doesn't work, I know I need to start tracing wires (everything looks good from what I can see, but then there's all the wires I can't see!) Will probably end up being a redneck setup with a jumper wire and a volt meter while driving down the road.
emiracleworker1
03-21-2012, 01:02 PM
Well, turned out to be the lt grn/blk wire with a break hidden high up in the loom. That took plenty of uncomfortable hours laying underneath to find!
Brakes are all done... and what pleasure having to remove the hub assembly, drive out the wheel studs, etc, etc. Now just to figure out why the rear end wants to come around on me when I hammer the brakes on a dirt road... I think this is going to be a never-ending project!
Brakes are all done... and what pleasure having to remove the hub assembly, drive out the wheel studs, etc, etc. Now just to figure out why the rear end wants to come around on me when I hammer the brakes on a dirt road... I think this is going to be a never-ending project!
j cAT
03-21-2012, 04:09 PM
Well, turned out to be the lt grn/blk wire with a break hidden high up in the loom. That took plenty of uncomfortable hours laying underneath to find!
Brakes are all done... and what pleasure having to remove the hub assembly, drive out the wheel studs, etc, etc. Now just to figure out why the rear end wants to come around on me when I hammer the brakes on a dirt road... I think this is going to be a never-ending project!
if the front brakes are all repaired the rear drums may need replacing especialy if there is a good sized ridge on the drum edge causing great difficulty in drum removal with the shoes hanging up on it.
if the shoes are worn at the top only the drums are too worn.
try adjusting them and see if you get better brake action.
Brakes are all done... and what pleasure having to remove the hub assembly, drive out the wheel studs, etc, etc. Now just to figure out why the rear end wants to come around on me when I hammer the brakes on a dirt road... I think this is going to be a never-ending project!
if the front brakes are all repaired the rear drums may need replacing especialy if there is a good sized ridge on the drum edge causing great difficulty in drum removal with the shoes hanging up on it.
if the shoes are worn at the top only the drums are too worn.
try adjusting them and see if you get better brake action.
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