I have had this car for many years and just recently started having problems. About a week ago I noticed that the transmission was slipping just a bit so I checked the fluid and it was a little low so I filled it. A couple days later my digital speedometer started going crazy moving from 0-50-0 regardless of how fast I was going. Then I got a speed sensor fault and the speedometer finally just stuck at 0 and stayed there and the car wouldnt shift out of 1st. I unplugged the battery to reset fault because I was told this may work. The speed sensor fault hasn't come back but now the car still won't shift out of 1st gear and the speedometer is still stuck on zero. I pulled the codes and here is what I got...

pc1520 current
pc0603 history
ip1552 history
pz1558 history
rf2560 history

I have searched the forums and found that a couple of these codes would have nothing to do with my problem but there were a few I couldn't find.
I quit driving the car because I bought an 03 Deville DTS but I would like to sell the 96 and need to fix this problem in order to do so. Any help would be appreciated!

 

No shift and a speedo that won't move is likely a bad speed sensor on the trans, or the wiring for the sensor.

P1520= Gear Indicator problem-Could be an issue with the MLP(Manual Lever Position sensor) or the wiring
P0603= PCM Memory Reset-Probably set when you disconnected the battery
IP1552= Instrument panel code-may have something to do with the speedo signal not getting to it
The other codes are not related to the speedo/no shift

 

Thanks.....it looks like that speed sensor is quite a job to replace. I was hoping it would be something else but that sounds like my luck. haha Im not sure what I'm going to do. Thanks again!

 

Actually, the VSS(vehicle speed sensor) in mounted on the pass side of the trans, right where the axle comes out of the housing. Fairly easy to get to. The wiring right there at the connector can get frayed, or the insulation can deteriorate, and the wires will short together, causing a no speed signal. The sensor itself can malfunction. Very simple to change. I would first check the wiring in the area for the sensor, and if I didn't see any obvious issues, I would swap the sensor.

 

Thanks for the help...I haven't had a chance to fix it yet...did pick up the sensor today. Hopefully this weekend I will be able to get it done. If this is the problem and I can fix it for the 17 bucks I paid for the sensor I will be VERY relieved!

 

BTW...after your first reply I thought you meant the input speed sensor that is inside the transmission. Thankfully (hopefully) that's not my problem.

 

Input speed sensor failure would not cause the speedo to not work. It would keep the trans from shifting, but the speedo would still operate.
I should have been a little more clear on which sensor I was referring to.

 

Well I changed the speed sensor today and nothing has changed...still no speedometer and still won't shift out of first gear. Any other ideas?

The p1520 error code that you said was a gear indicator problem...could this be the cause? The MLP sensor? If so where is the MLP sensor located?

I think that the speedo and shifting problem must be related somehow because they both happen at the same time...when I first started having problems and before the speedometer just completely quit working the speedo would go crazy and the car wouldnt shift but when the speedo went back to normal I would have no shifting problems...

Thanks again for the help!

 

The MLP should be on top of the trans, where the shift cable connects. A bad signal from the MLP could keep the trans from shifting, but it would not effect the speedo. Your issue is speed sensor related. You may have a wiring problem from the VSS(vehicle speed sensor) to the PCM, as I mentioned before. The wiring right at the connector can be damaged, or otherwise compromised, or it could be a wiring problem anywhere in between the sensor and the PCM.
The best way to diagnose this would be with a scanner connected, and monitor the input and output(vss) data. Accessing the on-board data perimeters(PIDs) could be done also, but it is confusing to some. I'd have to look up which particular parameter is the VSS input on the '96, but I don't have that info here at home, and I'm not sure if the '95 is the same...but it may be.
I can do a little looking and see what I can find here. The wiring diagram shows the VSS signal going directly to the PCM, so I have to assume the PCM sends the VSS signal to the instrument panel cluster(ICP). So, if we have no signal to the PCM from the vss, the speedo will also not function, along with no shifting....
I have seen instances where the VSS was working properly and the PCM was getting a valid vss signal, but the PCM was not sending the signal on to the ICP. In those cases, the trans would shift, but the speedo was not functioning, and the PCM was the problem.
A scanner would certainly help figure this out quickly...

 

The PID for the vss is PD12. Enter On Board diagnostics, and once it has run thru, it will display "PMC?". Press the "Warmer" button until you see PD12 displayed. Drive the car. The vehicle speed will be displayed there. IF there is no speed displayed, you have a wiring problem, or PCM problem.
If you're not sure how to enter/access the on-board diagnostics, please check out the "FAQ" section here to get the procedure for your year car.