I picked up a '94 Trans Am recently, car is in nice shape, runs real well. Some stuff on it didn't work but I know GM has horrible build quality and its 10 years old I expected it. I've fixed alot of the stuff but one problem has me befuddled. When I got it the power door lock on the driver's side would not work. The switches on the passenger and driver's side both work, however the actuator on the driver's side didn't work. No big deal I bought one from a guy on the trader and put it in tonight, still no worky!! Thought I got a bad actuator so I checked voltage at the actuator connector............nothing......nada. Hmmm should have checked this first before I dropped $20 on another actuator right?? Well the door panel is such a HUGE PIA to take off (and I basically wrecked mine tonight trying to get it back on ) I just hoped it was a bad actuator. So I tore off all the tape and bared the wires a tad just as they went into the harness in the door.......still nothing. So I ran each wire and found which side had 12v going to it.............assumed it might be a bad ground so I grounded the one wire to a good chassis ground-well it would not lock but not unlock. HMMMMM. Now i wonder WTF is up with this thing. Any ideas?? Is there a double pole relay underhood that maybe one side isn't working on?? How exactly does this power door lock system work?? BTW I'm a mechanic and have an electronics degree so this is a last ditch effort.

 

Your door locks work off reverse polarity. one side will read ground while the other is hot for lock. They change polarity for unlock. You problem is most likely the driver door switch or actuator. I just did a 94 today and the colors from the switch were dark blue and light blue. The car I worked on had a bad drive door switch but the locks still functioned. First start over. Put all the wires back to original. Then take a logic probe or a meter and check for 12 volts at the actuator. One wire will read 12 volts for lock while the other remains ground. Then check the other wire for 12 volts for unlock. If you see voltage at the motor but it doesn't move the actuator is bad. Its really hard to diagnose without being there but I hope this helps.

 

There is a power door lock schematic on my Tech Page if you want to test out your electronics degree.

 

Already checked that schematic and saw some symbols that aren't in my electronics book, apparently GM makes up a few symbols that aren't in any electronics book. So that schematic was no help (darn!)

Bt96ss I assumed that's how this sytem worked since there are only two wires going to the schematic. I have a switch that I know works but the plastic is broken on it , I'll try that tomorrow. Since I already replaced the passenger side switch the drivers side may be at fault. I'll keep this thread updated so if I finally get this solved , someone can search and find a solution if they have this problem.

****EDIT**** I got curious and went down to the garage and swapped in the switch that I knew worked to the driver's side. Still does not work!!!

I know the actuator is good because if I apply 12v to either pole it works, so I assume that since both switches are good, the actuator is good- something like a broken wire exists = not practically fixable

Moral??? Don't buy a 10 year old GM product!!! Unless you want a fast car for cheap that nothing else works on it

If GM would actually TELL you what these mystery symbols are on their schematics i could build a circuit that would work. Going to bed now and vowing I will NEVER, EVER buy another GM product. Even my 14 POS daily driver Talon AWD is built better than this.

 

Depending on the company they use different symbols and they also change them.

 

looking at the diagram it seems like your problem is a broken wire between the switch an the actuator. If there was a broken wire between the driver and passenger switch the whole system would stop working. But since you say that both switches work the passenger door it would seem to be something isolated in the driver door. What is the symbol in question that is hard to understand?

 

Exactly.

I don't have a degree, but I don't have any trouble with the diagram. Did you notice that neither lock will work unless there are good switches on both sides? So removing a switch from one side and putting it in the other won't tell you a thing.

 

Well then in theory if I switch the door lock switches from side to side, the problem should swap sides also??? Easy enough to check

The symbols I'm talking about are lableled "P500" and "P600" and look like little UFO's. Hmmm maybe area 51 has something to do with this

 

they look like gromets or places where a wire passes through a wall to me, but I could be mistaken. Just ignore those symbols and focus on the wires and switches, etc.

 

Well I just went down today for a bit and played with it. Update:

I have 3 good switches, no matter where I locate them it works the same way. Only the passenger side works. Both sides will work the passenger side with no problem.

From where the wires come out of the door harness, to the actuator plug I have continuity, meaning there are no broken wires.

I got out my voltage generator from electronics school and applied 12v to each pole of the actuator and it works fine. Old actuator works fine too.

Got even funkier, I worked the switch for the driver's side and figured out which wire was supposed to have 12v and which was supposed to have ground. I then manually grounded the "ground" wire when the switch was pressed to a chassis ground. It works both ways this way. So there is no ground in the switching action of the relay in the keyless entry receiver (I have an AU0 car). I get the 12v from the relay but not the ground. That's why my actuator doesn't work. So can I then assume its a bad relay in the keyless entry receiver (BCM??). Again an expensive fix.......

 

There is no BCM on a 1994. Try bypassing the keyless receiver to prove your theory.

 

Where is the keyless reveiver? Passenger side kickpanel?? How do I go about bypassing it??

 

Rob's right, no BCM. It sounds like the drivers side relay in the keyless entry receiver is bad. There are seperate relays for both sides. To test this theory pull the passenger side kick panel and find pins C & G, the wires are grey and tan. These wires will run the drivers side dorr lock motor. Put power to then and see if it works.

(info) the passenger lock motor shares the same grey wire on pin C and also uses a tan wire on pin H.

Good luck

 

Yes, in the kick panel. There are location pics and schematic of the keyless receiver on my Tech Page. Sorry, I thought you had already looked at the schematic.

 

Thanks guy, I dunno why I never use my electronics degree. After reading Shoebox's schematics it was rather obvious what I needed to do. I applied 12v to a tan wire on the plug and the ground to grey wire and by moving the ground and 12v around I was able to lock/unlock both door locks. I took apart the keyless entry controller and found what I assumed, it was basically IC's and not repairable. So I need another controller, its nice to know what was wrong!

So RE AND CHERYL & Shoebox thanks!!