Question: My prom was loose in my ECM, I reseated it and car is dead now. Crank no start. http://forums.corvetteforum.com/zerothread?id=546301
Is it possible that my Prom or ECM is dead now? Where do I get a new prom if I need one? How do I check the prom for functionality?

Thanks
Doug

 

The 90's ECM is riught above the battery, right? Any possibility that you ended up dropping something on the ECM case and the positive terminal of the battery and blew a fuse? I'd check the fuses in the first place.

To answer your questions directly, if your PROM is dead, it should still be able to fire. Do you have spark? Maybe something weird just happened and you lost spark control.

When you turn the key on, do you hear the FP run?

You can buy a new PROM either through forum member Jeff Kopp or through http://www.gmpartsdirect.com

It could have toasted the ECM in a really weird case, but you should still have some ECM functionality. Good luck, -85Y

 

Are you sure you didn't crush one of the pins when you reseated the prom. Those don't come out for no reason. I'd repull it and VISUALLY verify that you need make the problem worse

Kitt

 

I agree....crushed pins....that's not to say the ECM didn't take a dump..

Good luck,
Frank :flag

 

1. Fuzes were checked first, I always check those first.
2. There is a Vacuum Module(brake booster?) and a cross brace between the ECM and the battery, ALMOST impossible to make contact that way.(key word is almost, I am sure it could happen, just not in my case.)
3. I have spark and fuel to all 8 cylinders. My ignition control module(the 7 pin module in the distributor tests okay)
4. I have Code C12 in Module One CCM OK, and nothing but --- in module 4.7.
5. I regapped the plugs and put on a new distributor cap and rotor while I was in there, and the coil seemed okay, I had 8k-9k ohms across it. and continuity on the tapped side.
6. I can get the car to start now, but still wont idle for crap. I have .52 volts at TPS while closed and it goes up to 4.69 or so if I open it wide open.
7. I believe I have leaky injectors, Fuel pressure test spiked to 50 psi, and dropped to 42 psi immediately. Then I could watch it as it bled off fairly quickly. There are no external leaks at the fuel rails, ..... never really worked with fuel areas before.
8. I bought the car a couple of months ago and the prvious owner had reflashed it. Car had all emmisions removed, (which I had to replace to pass inspection, 160 degree thermostat gutted cats etc.). Apparently it wasn't pushed all of the way in, the cnx on the side weren't engaged. As far as crushing pins, I dont see how as they are more like a cable connector(similar to an IDE drive).
So I don't know where to go now other than to limp over to the dealer and get hosed. ....... any suggestions?

Thanks to all of you for your assistance,
Doug

ps: what is an FP? ..... fuel pump?


[Modified by Dougs 90, 10:37 PM 4/26/2003]

 

Its most likely normal for the fuel pressure to drop off to 42 PSI, thats about the correct regulated pressure. When you said it idle like crap, do you see lots of black smoke pouring out of the tail pipe like fuel is being poured through it? If so and if you have a scan tool check to see what is indicated as engine coolant temperature. If you dont have a scan tool check the coolant temperature sensor thats located near the thermostat of the intake manifold.

It will have a two wire connector with a yellow and a black wire, using an ohmmeter check the sensor resistance. At about 50 degrees you should get a reading between 4500 and 7000 ohms. An open circuit at the sensor will tell the ECM that it is -40 outside and it will pour the fuel to it. At 200 degrees the resistance is about 180 ohms.

Some of the early coolant sensors had a coaxial connector, meaning its round shaped sorta like the coax connector to the TV. Those old sensors would develope a coolant leak and under cooling system pressures coolant can be forced through the insulation jacket of the wire all the way into the ECM.

I have found several ECMs that had coolant intrusion in my years of being a GM technician several years ago. If you have one of those old sensors go to your dealer and purchase a new style sensor and a sensor pigtail connector assembly.

 

Doug-

Sounds like you've done your homework on this problem. Wish I could offer more assistance.

Some quickies. Yep...FP is fuel pump. But you mentioned that you have fuel and spark, and now it does run.

About the quickest test I can think of is pulling the ECT (engine coolant temp) sensor connector off of the sensor on the front of the manifold. If it runs the same, you probably have a problem in the connector or the sensor itself. The TPS looks good like you mentioned, but our speed density cars rely heavily upon the ECT being correct. Why isn't it setting a code if it is bad? Well, can't tell you that. I messed around with the ECT circuit for a while when I was having problems with my MAF system (before I changed over to speed density) and used a rheostat to control the 'temperature' (actually resistance) for testing. I fed it some pretty insane values and didn't get a code until I went all the way high or low.

If it was a problem with injectors leaking down, I don't think the problem would have become apparent all of the sudden, but I've seen some pretty weird things before. Good luck and keep us updated on the progress. -Matt

Edit-Just saw tjwongs' post and realized I pretty much said the same thing...sorry about the repeat of info.


[Modified by HighHopes85, 1:30 PM 4/27/2003]

 

Thanks Everyone. I replaced the Engine Coolant Sensor and a put a new pigtail on it when I got the car. The knuckleheads that did my inspection said all of the emissions stuff had to go back on. Well, somehow they managed to bust the connector, I got a code about a week later when the connector fell off. I went ahead and replaced both the sensor and the connector. I guess I am going to limp over to the dealer tomorrow morning. Let them hook it up to theur computer, I have no way of scanning. I just use the display. Well I tried my best, all in all not bad for a newbie mechanic. I have learned alot since I got this baby a couple of months ago.

Thanks Again
Doug