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Dave Nova
Dave Nova, Buick Technician
Category: Buick
Satisfied Customers: 18959
Experience:  ASE Master Certification. GM World Class Certification
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1996 Buick Skylark: L..Automatic..car ran and drove fine

Customer Question

1996 Buick Skylark 2.4 L Automatic. Car was wrecked last February, body work was repaired and car ran and drove fine. Two weeks later the engine would run intermittently and finally quit. Took it back to shop. They said the computer was bad. Installed new computer. Still wouldn't run. Took it to dealership. They diagnosed a bad key switch and replaced it. Blew up the battery in the process. NEVER took car for test drive. Went to get car and now the transmission won't shift from first and the intdicator on the dash doesn't work and the est light is on. Had technician diagnose it and he said it was the switch on the shifter. Replaced it and nothing has changed.
Submitted: 4 years ago.
Category: Buick
Expert:  Dave Nova replied 4 years ago.

Hello and welcome to justanswer.

 

Does the speedometer work while driving?

Customer: replied 4 years ago.
Yes speedometer works
Customer: replied 4 years ago.
Starts in park and neutral reverse lights work.
Expert:  Dave Nova replied 4 years ago.
If you place the shifter in Low 1 range and take off, then shift to Low 2, will the transmission shift into second gear?
Customer: replied 4 years ago.
No it will not shift
Customer: replied 4 years ago.
I have checked all the fuses as well
Expert:  Dave Nova replied 4 years ago.
In the underhood fuse panel, locate the ERLS fuse, then test for power at this fuse using a test light or voltmeter. Make sure the key is on while testing. Let me know what you find.
Customer: replied 4 years ago.
ERLS fuse has 12 volts on both sides. Does the engint computer also control the transmission? Is there a connection under the instrument cluster or the transmission which could have been inadvertently undone by a technician
Expert:  Dave Nova replied 4 years ago.

The engine control computer does also control the transmission. There is a connector on the transmission itself that could be unplugged. This connector is on the front side, facing the radiator. #7 in picture below.

 

 

 

graphic

Customer: replied 4 years ago.

Thanks for the picture, the plug appears to be locked in and in good condition. I unplugged and checked the connections on the computer and they all appear good. All pins straight etc. My parts car is a V6 would it hurt to try that computer and see if transmission problem goes away?

Expert:  Dave Nova replied 4 years ago.
You could try the computer. I would at least check the wiring first. At the transmission connector, test for power on the pink wire. Make sure the key is on while testing. If you have power on this wire, then proceed with trying the computer.
Customer: replied 4 years ago.
Pink wire was hot with key on. Computer is different and won't work. Going to see if NAPA will give me a warranty on it. Unless you have a better suggestion.
Expert:  Dave Nova replied 4 years ago.
The only thing you can do besides replacing the computer is to ohm check the wiring between the transmission connector and the PCM(computer)
Customer: replied 4 years ago.
Unfortunately I don't have wiring diagram to check continuity between the pcm and the transmission. Napa warrantied the computer and I installed it. Now I have a whole new set of problems. ETS OFF light is not illuminated anymore but selector indicator is not showing where the shift selector is. Radiator fan stays on, coolant light is on, alternator light is on, oil light is out with the engine not running. Trouble codes p1886 and 1810. Does the pcm need to be programmed at dealership to match the car?
Expert:  Dave Nova replied 4 years ago.
On all 1996 and newer GM cars, the PCM does have to be programmed to the vehicle by the dealer.
Customer: replied 4 years ago.
vehicle was programmed by dealer. where can I get wiring schematic to start tracing wires to transmission pcm?
Expert:  Dave Nova replied 4 years ago.

Here is the schematic.

 

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PCM Connector C3 Blue

 

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Transmission Connector

 

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Customer: replied 4 years ago.
Performed continuity test through each wire to pcm all had continuity and no shorts to ground. I checked for continuity from erls fuse through each of the transmission solonoids at the pcm TCCPWM sol had 11.2 ohms, 1-2 SS had 22.4 ohms, 2-3 SS had 21.8 ohms, TCC SOL had 21.4 ohms. I don't think I have a problem between the transmission control valves and the pcm. Can you provide schematic between transmission selector switch and instrument cluster and pcm. I am still leaning toward the technician messing with something in there whenn he installed the new ignition switch.
Expert:  Dave Nova replied 4 years ago.

There is no switch on the shifter, the transmission range switch (neutral safety switch) is located on top of the transmission. This is likely the part that was replaced.

 

Here are the schematics for that circuit. At the PCM use the connections noted for VIN T.

 

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PCM Connector C1 Black

 

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PCM Connector C2 (Gray or Clear)

 

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Park/Neutral Switch Connectors

 

graphic

 

 

Dave Nova, Buick Technician
Category: Buick
Satisfied Customers: 18959
Experience: ASE Master Certification. GM World Class Certification
Dave Nova and 12 other Buick Specialists are ready to help you
Customer: replied 4 years ago.
I checked for continuity at the plugs going into the pcm. If I read the schematic correctly it checked ok. Here is what I found. C2-21 is D C1-20 is B C1-21 is C and C2-26 is A. In Park continuity between D & A, In Reverse continuity between D & B, In Neutral continuity between B & A, In Drive between B & C, in 3 between D & B & C & A. My son who owns the car really wanted to drive it, took it around the block and the speedometer pegged to 120 and stayed there. I drove it around the lot a bit and when I got to 25mph or so it started working again. Cluster display still doesn't work. When I was driving it around I tried shifting manually to no avail. Does that shed any light on the problem.
Expert:  Dave Nova replied 4 years ago.
Since the speedometer is acting erratically, check the connection and wiring at the vehicle speed sensor. This is on the transmission near where the passenger side axle comes out.
Customer: replied 4 years ago.
I am giving up. The computer is simply not commanding the transmission to shift. I am planning on taking it into another shop. Thank you for all your assistance. It has been greatly appreciated.
Customer: replied 3 years ago.
Hello Dave, I took the car to a very reputable shop and they tried to find the problem with the car. They replaced the pcm, transmission switch, and the ignition switch as well as other checks and were unsuccessful. I still believe the problem is related to the fact that the dash indicator doesn't show the gear selection. The last time I drove the car I noticed that the car doesn't engine brake in D or 2 but does in 1. I don't know if that is relevant. We are going to get rid of the car unless you can come up with some last ditch idea to fix it. Thanks XXXXX XXXXX

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