My Brother recently gave my son a 1999 Saturn SL2. My brother worked on it extensively. It has multiple problems don't know if its related to each other or not. The car has problems stalling in idle most of the time. When stopping at a stop sign or light sometimes it stalls on acceleration. The egr valve is good and has had new spark plugs and wires. The coolant fan only runs when the air conditioning is on, if the a/c is off the car overheats. We have replaced the coolant temp sensor and now the gauge works but the fan still doesn't kick on without the a/c. Two months ago my son took it out and it wouldn't start which happens on occasion (not triggering the passlock system, I have another Saturn that does this). When you get in the car there are multiple things that happen when you know it will not start such as the windows won't function with the key on and dome lights do not come on, when the two of these happen we know it isn't going to start and it doesn't. If we let it sit a few hours or days it usually starts again. This time it hasn't started in two months. So we have it sitting in our garage and are banging our heads against the wall. Could all of these problems be related to a bad pcm? Is there a way to test the PCM? I cannot afford to spend a ton of money on this car but on the other hand my son just had a new $350 exhaust system put on this car along with a coolant sensor and fuel filter and my brother put a ton of work into it too and we hate to scrap it after my son has spent $500 of his own money on the car and he just started college.

 

Are you getting a Service Engine Soon light? Even if the light is not on, there may be a pending code that will solve this.

The PCM is probably the most reliable thing in this car. I'm kinda leaning to the crankshaft position sensor but I'd like to see that backed up with a code.

 

The check engine light never illuminated. I believe my son said it briefly flashed once.

 

The truly sad part about this story here, is that while creating a computer controlled car that electronically dealt with not only the complexity of running the engine but in addition the routine matters of doing things like turning on interior lights when doors are close, locking them when required and starting the car properly when initially starting it if the computer (the PCM) is causing a problem, and it is a device that talks to the other computers that run the body or the transmission you can spend a lot of money guessing what is going on all while having no idea.
A 1999 Saturn should have I believe a full OBD-1 logic series PCM in it and frankly it may very well be worth the hundred or two hundred dollars to actually purchase a scan tool to try to to figure out what is going on with it. Shade tree mechanics no longer can fix a lot of things with a wild guess and some intuition. There is just too big an area of technology now that it takes to make them work to be able to do that.
It would not be a waste of money to do so as OBD-1 and OBD-II logic is now pretty much a standard and a scan tool should be usable pretty much up through vehicles manufactured today. At least at the present. Last year I spent time chasing a scan tool down that would read my 94 Saturn PCM which seems to have a Pre-OBD-I form of soft ware and found there were non available any longer, but got lucky and ran across a used "Tool Truck" scan tool that had not been kept up to date and had been replaced that was old enough to cover my Saturn and another OBD-I car I have so it works for me. It does not cover OBD-II but at the moment I do not need that but if I did I would stop down to O'Reilly's and purchase what ever they have that would for a C note or two. It is still cheaper than throwing parts that I have no clue whether they are needed or not at a problem I can not define with out a scan tool.

 

The car has acted like it had a dead battery for the last couple of months though charging or jump starting it didn't work. Last night we checked it again wondering if the battery could be bad and it started right up without a problem and runs fine. Though today I took it to Autozone because it was the first time the engine light illuminated. They came back with two codes P0702 which is Transaxle actuators lost power and P0108 which is Map or Maf sensors. Two minutes later we started the car and both codes had cleared the light was off. But when I got to autozone the "dinger" was sounding with the car off and the keys out,as if we left the headlights on or the key in the ignition. The Autozone employee pointed out that he could put the car in gear with no keys. After it was started and keys removed again it quit. The sensor we put in was a Valucraft/Coolant Temperature Sensor Part Number: SU1131VC from autozone and the connectors were clean and not corroded. Today the low coolant light was flashing along with the temp light, on the way home it was not, even though the coolant was full. The fan still didn't run unless the a/c was on. There was no miss in the engine today.

 

You can get a scan reader for about $60 and for all practical purposes, that is all you need. You are OBDII, not OBDI. P0108 is the MAP sensor but the problem could be due to a vacuum leak near the sensor. The sensor could be clogged up as well.

The fact that you are getting codes means that the PCM is not likely to be bad.

This car is very sensitive to the coolant temp sensor. Any replacement type should be the brass tipped one and not the ceramic tipped. Valucraft is not AutoZones top of the line products. If they had a Duralast brand, that is the one you should have gotten.

The low coolant sensor is inside the coolant reservoir and it is very sensitive. You only need to be about an inch down to trigger it.

The cooling fans do not come on until the temp gauge is almost to the red. If you are only going to half or 2/3rds the way up the scale, you aren't overheating yet.

 

update?

 

It ran ok for a couple of small trips. Then it died again this time the headlights still worked and the power windows but the power locks did not and it would not start. I picked up my son and had him leave it for a few hours. went back with plans to tow it myself after dark since it was a couple of streets away and this time it started. We drove it home and haven't driven it since. When I say it overheats I mean that the fan doesn't kick on at all when the a/c isn't on the coolant will actually start overflowing out of the reservoir onto the ground, when you switch on the a/c it stops immediately after the fan kicks on. My brother said it has done that for a while and he cannot figure out the problem. He said it doesn't happen when it is cool out or during winter. It usually happens in the summer months or when sitting in idle for sometime. I live in the north and its cold here, I would like to figure out the problem. It isn't desirable to run the a/ when its 0. Thanks again for your help!

 

Carefully looking back through the thread, I do not see any reference to the temperature coolant sensor other than a suggestion it should be replaced. The location of the sensor is the drivers side of the cylinder head at the end. Nor do i see any indication that the heat gauge is indicating over heating or running hot, only the statement that the coolant gets barfed out indicating the thing is running hot.
The fact that the fan runs when the A/C is on but not when it is off, is an indication that all things considered, engine control computer is doing what it is supposed to do, that is one of the two ways that fan is supposed to work. It always comes on with the fan if the A/C is being used. That is an indicator that the fan curcuit is capable of working correctly.
The temperature cooling sensor's duties in running your car are weighed in with importance far above the basic function of letting both the computer (for the purpose of generating error codes, seeing to it the computer functions correctly in operating things and a list as long as your arm) one of which is giving you accurate information as to engine temperature. That you have not mentioned that the heat gauge is telling you the engine is hot! There for if the gauge is not reading engine temperature correctly the odds are the information the computer does not have accurate data either. Thus if a lot of weird things are taking place, among them, inaccurate heat gauge information, the rule of thumb is to change the bloody sensor.
Which is exactly what I would do if he car were mine, but I would have changed it long ago.
The second part of this problem is that the exact value of that sensor some how was kept a secrete or something like that from the people who make these sensors for the auto parts stores and the wrong value was reverse engineered and became a standard aftermarket part. Along about 1999 ( the year of your car) a service bulletin was issued that indicated aftermarket was saturated with improperly calibrated sensors however after about 10 years of making the wrong part for NAPA and others all over the world, that part seems to have never been made correctly thus the only place to buy that part and insure you have the correct one as that sensor value is overly important in the correct operation of the engine of the car, is to find a dealer that will sell you Saturn parts and go to the parts department and order it, AND the connector repair kit and install it. Since conveniently there are NO MORE Saturn dealers around it will take a bit of investigation on your part to call and ask if Saturn parts are available. For my purposes there is a Chevy dealer with in a 10 min drive of the house that actually has a sign on their property that says they will service Saturns!!! Which is kinda nice as the VW dealer next door occupies the old Saturn dealer ship so I did not have to look far for one. They have been more than willing to look up and order specific Saturn parts for me as there are a few other Saturn unique parts that are also imperfect and not worth buying from anywhere other than the dealer.
However aftermarket has a lot more parts than I thought they did that are good buys financially and also fit and work. Please change that sensor if you have not as yet and from your writings here, it seems that you have not and let the forum know what happens.

 

A quick check of the PCM is to see if the SES light comes on for about two seconds right after start and then goes out. If it does that, the PCM is good. Next step is to turn the key to the run position and see if the SES light comes on. If it does not come on either time, then it could be a bad bulb or connection in the circuit or a bad PCM, but as I said before, the PCM is really reliable.

I am concerned that the fan has to come on to keep it from overheating. The fan in my Saturn never came on, even when pulling the grade out of Death Valley when it was 121°F. The gauge got up to a little over half way and I was running the AC so the fan was on although I did put the vent in recirc and turned off the AC from time to time to cool the engine and during those times, the fan shut off.

The rangers at Death Valley recommend not running your AC pulling that grade but no way am I going without AC in those kinds of temps. So I put the vent in inside air (recirculation) and as the temp gauge rose to two needle widths above the halfway mark. I would shut off the AC and because I was not drawing in any outside super hot air, the cabin would stay cool for about two minutes. During that time, the temp gauge would drop to the normal two needle widths above the quarter mark and then I'd turn the AC back on. It was about 5 minutes on and 2 minutes off.

Now I had the manual transmission and the SL1 engine so I didn't have the added heat of the automatic that you have to deal with, but I still don't think you should be overheating with the AC off. The things I would look into are the coolant being between 50 and 67% antifreeze and clear(colored but clear), the radiator cap holding pressure, the bleed line free to vent any air bubbles and the water pump circulating the coolant.