Mechanics

POSSIBLE PCM PROBLEM?

1998 Saturn SL1 • 263,000 miles

I just purchased a used saturn. After 30 or so min of driving and 5 or so minutes sitting idle the vehicle started to overheat. This is what I've troubleshot so far:

1. There is no leak in the cooling system.
2. The fan does not come on, ever, even when the AC is running.
3. The AC is fully charged.
4. The fuse for the fan is not burned out.
5. No problems with the thermostat.
6. The fan works when directly wired to the battery.

I brought it in to be scanned, thinking that maybe it was an engine coolant sensor, or some other sensor issue & it came back unable to scan.

A mechanic friend of mine said it sounds like the computer is out. Here is the problem with that. Everybody seems to call this part by a different name. I've heard Powertrain Control Module, Engine Control Module, Engine Control Unit, and Engine Control Computer.

I read in a previous post that the location of the PCM for my particular make and model is on the driver's side under the dash. I removed this part and brought it into an autopart's store for replacement. The clerk behind the counter said that I had pulled the wrong unit. He claimed the unit I brought in is the Transmission Control Unit & therefore I am not eligible for the refund on the core. The part I removed specifically says "Powertrain Control Module". He claims "powertrain" means transmission. He also stated that the parts look identical, so that is also why I'm mistaken. My understanding is that "powertrain" it means engine, transmission, driveshaft & everything else that powers the vehicle.

So my question is, simply, am I right or is the clerk? The fact that everyone calls the same part by 4 different names is confusing enough, and this is the first I have heard of the term Transmission Control Unit. Also, there was only one unit mounted, not 2 identical units as claimed by the clerk. So if the clerk is right & this is the TCM, then where would the PCM be?

Your help and advice in this matter is much appreciated.
Avatar
Reuptake
August 29, 2011.




Your possibilities here could be the fan relay, coolant temperature sensor and the computer controlled of the fan relays circuit


Tiny
Rasmataz
Aug 29, 2011.
Just to add to this one if you have a automatic transmission the engine control module and the transmission control module are combined into one unit called the powertrain control module. Heres the best way to test the pcm fan control driver the fan motor relay etc. Put your old pcm back in start up the car unplug your coolant temp sensor. Did the radiator fan come on?If it did replace the coolant temp sensor also inspect the terminals to the coolant temp sensor if they are blue or green instead of silver replace the connector also because the terminals are corroded. Let me know what you find I have never seen a bad pcm cause the fan to not come on but anything is possible. Before you go replacing the pcm try what I asked and get back to me on what you find.


Saturntech9
Aug 29, 2011.
It's not the fan relay. I forgot to mention that I also checked that.

The car is an automatic, and it's good to know that the PCM is a combination of the ECM and TCM, as I thought. Maybe the clerk was looking at parts for a manual by mistake. Regardless, I will be purchasing the part at a different autoparts store, if needed.

I'll check the ECTS first thing in the morning & let you know how it goes.

I'd also like to mention that the check engine light, temperature light and battery light are all on. The main reason why the PCM was suggested to me is because the scanner was unable to communicate or receive any codes. Is there any other reason, other than a faulty computer, for a scan showing up as unable to communicate?

Thanks for all of your help.


Tiny
Reuptake
Aug 29, 2011.
Scan the computer for codes and get back if any present-


Tiny
Rasmataz
Aug 29, 2011.
Does the scan tool power up off the obd2 connector?Yes you could have bad wires or terminal connection issues from the od2connector to the computer. You say the battery light is on have you had the battery and alternator tested yet?Also made sure the battery cables are clean and tight?
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Saturntech9
Aug 29, 2011.
I am an ASE certified tech and i've run into a problem with a 98 saturn 1.9 SL1, when I went to scan the vehicle also had a no communication problem. After doing pin testing it lead me to believe that I have a faulty PCM. So the only real way to tell if you have a faulty PCM is to do pin testing. This allows you to check each curcuit individually.


Tiny
DansAuto
Apr 27, 2012.

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