97 Pontiac Sunfire Wont start and no dash lights?

When you replaced the "fan motor" are you referring to the radiator fan or the fan in the dash that blow the air out your vents? Why did you replace the fan motor? Have you tried a jump start to rule out a weak battery?

I replaced the radiator fan motor. It wasn't coming on when hot or when AC was on. I could smack the back of the fan motor and it would come on for a few minutes then die again. After replacing it the new motor worked perfectly. The original motor had become weak over the past few weeks and I briefly had it straight wired to the ignition at the wiper fuse as the temperature was slightly higher than usual at times. I reconnected it properly 3 days ago. I didn't notice it had become weak until using the new motor and seeing how much more powerful it was. I checked the fuse panel where it was connected and found no damage. All the fuses are fine and getting power when tested with didital multi meter. I do not have a good wiring diagram but I am getting power at the wires going to the ignition switch. The battery is good. I even tested with another battery from my moms 02 Cavalier.

I just replaced the ignition switch with no luck.

What is the problem you are experiencing? No electrical power anywhere in the car, or the engine won't start?

Both. The battery is fine. The interior lights come on and the horn will blow. The headlights and emergency flashers will also come on but nothing else. When I turn the key nothing happens. No lights on the instrument cluster or anything.

Have you checked all the fuses under the hood? There may be some with a plastic cover over them that you can not use your multi meter to check so you have to look very closely to see if there is an open circuit. Also try swapping relays around, don't mix and match relays either, just switch identical parts and see if that changes anything. Also, have you performed any recent work? Could any wires have been crushed? Do you know where the starter relay is? Have a helper go inside car and cycle the key from start to off repetitively, if you go under the hood you should be able to hear the starter relay click and feel it move if you put your fingers on it. Let me know what you find.

Thank you. I did all that. There is no power coming from the ignition to the starter relay. I have tested every fuse, relay, and fusible link. Even the ones that have nothing to do with the problem. The fan motor is the only recent work I've done on the car. I tested everything in that area including testing the starter. My multi meter picks up power going to the ignition switch but still nothing. The PCM is getting power also. I can't even scan for codes. When I put the key in the ignition I get the usual dings but when I turn absolutely nothing happens. There is no voltage drop on the battery when the ignition is turned to start either.

There is some additional information I feel I should share. 3 weeks ago the theft system light came on but when I turned the car off and back on it went away. It never happened again. The theft light would come on when turning to ignition on sometimes but once I started the car it immediately went off just like the check engine and ABS lights do. It never did this before that. I can also confirm that the fan relay does not recieve a signal from the PCM to start the fan when it's hot. I have had to leave the AC on and it would stay on like it should with the AC. The temperature sending unit was replaced twice before tracking down the wire from the PCM to confirm no signal was being sent despite the sending unit working properly. This problem has existed since February. The car has a salvage title and was involved in a front end collision several years ago. I have opened all the main wiring harness sections especially along the front of the car but find no damaged wiring. Other than the fan issue the car ran great and just hit 150,000 miles.

You mentioned that you can not scan for codes? Do you have a scanner/code reader that you are using? Does your device communicate with the car's computer at all?

When I plug it in, it says connected but when I hit read it says unable to scan and tells me to make sure the key is turned to on etc.

I also just noticed something. Using my multimeter I can probe into the yellow wire of the ignition switch which goes out to the starter. When I turn the key like I'm going to crank it, it reads 0.14 volts. I was expecting to get no reading at all.

Before playing with the ignition switch I would worry about getting the computer to work. Can you read the data stream with your scanner? Of so do the readings look normal?

The scanner will not read anything. 2 different scanners and both say connected when plugged in but neither can read from the computer. When I turn the ignition switch to on and to crank, nothing happens. The battery is tested 100% fine.

Don't worry about it not cranking right now. You need to figure out why the computer is not working. Have you checked all fuses inside car and under hood? Have you tried swapping relays around?

WOW! I have this problem posted all over the internet in many forums and you are the first person to say the computer is not working. I keep thinking the computer must be fried and everyone keeps saying "no, that can't be it". All fuses have been checked. Even the ones that have nothing to do with it. I'm on my second multi-meter from checking and rechecking wires etc. I swapped the relays around and even tried some I had from past vehicle (I'm a bit of a hoarder like that). Here is what I recently posted on another forum thinking the pcm (computer) is totally dead:

I opened the PCM but saw no physical signs of damage. There are other reasons why I am beginning to suspect the PCM though.

1. For the past year the oil light will come on at idle once the car is warm. I know there are many things that can cause this. The sending unit was replaced and it still did it. Using a pressure guage it tested in the normal. Sometimes it would never happen at all but in the past few months it always did it. Still shows normal under guage tool.

2. Over the past year the car will be at idle and start to shake and sputter and sometimes die for no reason and no check engine light or pending codes.

3. The theft system light came on about 3 weeks ago after the car seemed to lose power for a brief moment. After I turned the car off and restarted it was gone. Since that time the theft system light has came on during "lamp test" when the ignition is turned on but went off with the rest of the lights when the car was started. I do not recall the theft light ever illuminating during "lamp test" before this time. (I may be wrong and just never noticed).

4. Over the past 2 weeks. The car will lose power very briefly even when at 35 to 65mph. Like a missfire but the gages all drop slightly then shoot right back up. Still no codes. (In my experience this type of behavior will set a code in most OBDII cars). It has done this 4 or 5 different times over the past week.

5. I can confirm that the PCM for several weeks and possibly even months (dating back to cold weather) will not send a signal to start the fan. (Mechanic shop confirmed this). I had to run the AC for the fan to come on. This was confirmed on a cool night a couple weeks ago when I turned the AC off and the car ran hot waiting on a train to pass.

6. The old fan motor which was replaced the night prior to this mess had a short in it. Once the car ran hot and the fan was identified as being weak I could push down on the connector and it would speed up but not to full power and if I let off it would die or reduce fan speed. If it didn't come on at all I could hit it on the back and it would start. This along with the fact that the fan has not been getting a signal from the PCM to turn on make me think that maybe a short in the fan somehow damaged the PCM. The new fan ran perfectly without issue but still would not be turned on by the PCM. (And yes all other related items were checked. I even replaced the temperature sending unit 2 times and all relays fuses etc are good).

7. My father in law next door likes to use my car to jump start his riding mower which doesn't even have a battery in it. I told him to stop last summer after he melted my jumper cables but I think he waits till I'm not home and does it anyways.

With all this in mind can anyone think of anything other than the PCM that would cause my symptoms? Some of the stuff above may have nothing to do with the PCM. Can the short in the fan motor even have any effect on the PCM?

I have even tried to get people to remove their pcms from 97 -99 Cavaliers/Sunfires to see if the symptoms match up. No takers though. Would a bad instrument cluster cause this? The PCM and cluster are the only 2 things I can think of.

What state do you live in Doug? Very hot weather/temperatures can cause a computer to crap on you. You mentioned that you used a multi-meter to check for voltage, have you used a test light at all? Have you checked for pinched wires and/or wires melted to the exhaust?

Is there an alarm and/or remote start system?

I live in Forest City NC. Very hot here this summer. High 90's every day with no relief in sight. The humidity is the worst. Yes, I have used a test light. The only thing I haven't focused on is the transaxle range switch but I don't think it would cause all of this. There is no remote start or security system installed. It's actually a base model BTW. It doesn't even have cruise control or tilt steering. LOL.

Don't worry about the tranny range sensor. What circuits have you used the test light on? What symptoms prompted you to test the circuits and have more problems occurred as you performed tests?

I've used it on the ignition switch, on fuses and the fusible links. I've even used it on the PCM connectors to confirm that it is getting power along with the multi-meter.

You can not use a test light on any computers or circuits that run into computers, only a multi/volt meter. Very possible you put current where it doesn't belong through the computer with the test light. Try swapping it with a new part, that's the next step from here.