'92 Bonneville Electrical Problem

Hi everyone.
I'm trying to troubleshoot my '92 Bonneville. I was driving it a few months ago when it started to sputter and then stalled. I had it towed home. I just started looking at it a few days ago because of the warmer weather. I tried some ether in the air intake but it didn't help. I then tried for a spark from the coil pack but there was none. I took the coil pack off and tested it with a multimeter and each of the three packs gave me the same result. I'm not entirely sure if that's a good or bad thing because I'm not familiar with a multimeter. I just assumed that all three gave the same result and it's unlikely all three went bad at one time. Then took the ignition control module (from under the coil packs) to Murray's to have it tested. The guy seemed kind of new at it so I'm not sure if I trust his word 100% but he said it was bad. I plan to replace it when I come across an extra $150 but in the mean time I wanted to test some other things. I tried testing the harness that connects to the ignition control module but I didn't a current through it with my continuity tester. (black to the negative on the battery, red to each of the many pins in the harness) None of them turned the light on. Is there any specific way of testing this? I'm not sure if it's actuaclly getting power or not. On top of that, I was told the ECM could be bad also. I found it, but is there any way to test it? Maybe test for voltage going in and coming out? If I do have to change the ECM, will I have to get my keys reprogrammed? Thanks a whole bunch in advance.

Set the meter up to test 12 volts dc. Confirm the meter is set correctly by checking the battery. Red meter lead to positive terminal & black meter lead to negative terminal. Meter should be reading 12 - 13 volts.

Now to check for power going to ICM. Remove the wiring connector going to the ICM. With the key in the run position put the black meter lead on the negative battery terminal and the red lead on the terminal for the pink/black wire on the ICM harness. Should have the same reading as the battery.

Let us know what you find & we'll continue from there.

Hi Sir, thanks for your time.

I did what you said. I know how to check for voltage, just not sure how to check for resistance or ohms or whatever for the coil packs.

Anyway, I get the 12v reading between the battery terminals, between the positive terminal and various ground points under the hood, and from the positive line from the alternator to various ground points.

All my lights and other electrical things work fine. The car cranks...just doesn't start.

I took some readings from the negative terminal on the battery and each of the pins in the ICM connector. Some give 0v, some give .06v, some give .3v, and one of them gives 1.2v. However, none of them give 12v. And from here I'm dead in the water. I have no clue where to check next. I'm pretty handy and and can figure most things out but I just need a little direction. Where does that harness originate?

I took some pictures to better describe some details. You can see the small burn mark on the photo of the ICM. The guy at Murray's pointed it out. What could cause it to burn? The bottom of the coil packs that sit on it are untouched.

Next, I found this toggle switch next to the diag connector when retrieving the error codes. I'm not sure what it does. If you flip it one way, nothing happens. If you flip it the other way, the dashboard lights and headlights quickly flash once. All electrical testing I do is done twice -- once in one position and once in the other. I'm not sure if it's a kill switch or what that might be killing current to the ICM.

Again, thanks your time.

http://s199348096.onlinehome.us/files/bonneville/icm.jpg

http://s199348096.onlinehome.us/files/bonneville/killswitch.jpg

See if by flipping it one way or the other you loose power to the ign switch, icm or pcm, or just splice the wires together for now. Have the icm tested at Autozone or NAPA, it looks bad from that melted spot. For ign circuit diagrams check autozone.com/repairinfo. If the icm tested bad, and you have 12v to the icm once you track the wiring down, replace it, what else would you do.

Check fuse #6 under the dash on the passenger side. Replace it if blown then turn the key to the run position & see if it blows again. If not see if it blows while cranking.

Fuse #6 is not blown and does not blow. I connected the multimeter to it to just for kicks and there's 12v running through it.

What does the 0v, .06v, .3v, and 1.2v mean at the end of the ICM harness?

I'm afraid if I purchase a new ICM for it and there's still no or proper current to it, it's money wasted.

I've never seen anyone not have power at the pink/black wire without fuse #6 being blown. This is fuse#6 on the passenger side. It also supplies power to the fuel pump, can you hear the fuel pump?

The other wires at the ICM harness go to the PCM, cam & crank sensors. I don't know what readings any of those wires would show. Sometimes the oil pressure sensor shorts out & blows #6. As you said it wouldn't make sense to spend any money on parts until you find out why the pink/black wire isn't getting power.

You know what, I'm sorry. I really hate wasting people's time. I checked #6 next to the emergency brake pedal. As soon as I get home from work I'll check it on the other side. Would it be near the ECM? When I took that panel off I remember seeing the ECM itself but can't remember what else was in there. Thanks again. I really appreciate it.

I had a few minutes to myself so I stopped at home and checked it. The 20 amp fuse was blown. I replaced it and turned the key to the "on" position and checked the harness. Now there's 12v to the pink/black wire. Then I cranked it to see if that would blow it. It didn't. I put everything back tohether to see if it would start. Nope.

I guess the next thing to do is to replace the ICM...?

(still not sure if that toggle switch is killing everything or not)

OK - glad we got that little mystery solved. Keep a close eye on that fuse until we get it started.

Now that we know there is power to the ICM You need to check for spark again. I like to check at all three coils so we can rule out a bad coil.

Assuming you have no spark you now have it narrowed down to the ICM, crank sensor or the wiring between the two. Since the fuse was blown I'd bet it's the ICM. Have you considered getting a used one from the junkyard? Many like to upgrade from the Magnavox to the Delco ignition. You should be able to get the ICM & coils from a junkyard for under $50. Hopefully in $30 - $40 range. I think you also need the mounting plate when switching to the Delco system. http://www.bonnevilleclub.com/forum/kb.php?mode=article&k=99&highlight=magnavox

Edit There's no telling what someone connected that toggle switch to. The engine ran before so I doubt it has anything to do with the current no start problem.

I HATE crank and cam sensors.

At any rate, one of my friends has a '93 Lumina sitting in his back yard. It also has the 3.8 engine. I've heard that manufacturers use the same engine for many mondels and years so do you think that the ICM would match? I was going to eyeball it and cross my fingers. I know that there's a possibility of differences I can't see on the inside of it.

Do you know what would cause either the ICM to burn or that fuse to blow? Could the fuse have blown because of the ICM? I just don't want a repeat (although now I know where to look!) when I'm on my way to work.

I'm going to go out there to test for a spark right now with the original ICM.

We're getting close, I know it!

I would expect the Lumina ICM to work if it's a 3.8, being a 93 it might even have the Delco system. The Delco system has 3 individual coils so it will look quite different but still work. As mentioned before you'll most likely need the mounting plate from the Lumina.

You were spot on. The Lumina has the Delco type. I took the Delco ICM to Murray's and they said it passed. I then tried it in the Bonneville and, with the new coils, and none of them gave a spark. Oy!

I tried it with the switch both ways and I checked the fuse each time too. The fuse is still good.

I noticed that as long as the harness has power and is connected to the original ICM, it sparks between it and the mounting plate if moved around. I assume the case of the ICM is supposed to be grounded. (mounted properly) When I tested the Delco ICM, there weren't any sparks. I guess that could also just be proving that something is wrong with the original ICM.

But here we are with an operational Delco ICM and still no sparks. I've already replaced the cam position sensor. You mentioned the crank postion sensor...how much harder is that to replace? I looked around and read it was near the bottom of the engine, below the cam sensor. (I think) I already priced it at Murray's for $31.

Last for this post, is it ridiculously important to have the battery feed connected to the alternator during this? The bolt snapped as I was removing it the other day so it's not connected. I have been cranking it while it's connected to another running car, though. I didn't want to leave anything to chance.

Thank you, Sir.

Was the Delco ICM mounted? It needs to properly grounded.

Are you getting a reading from the tach while cranking?

I don't know if the alternator being hooked up would matter or not. I really don't think it matters but I'm just guessing.

I haven't had much time to work with it over the last few days. I hope to be able to get more into by the weekend. I'm going to try to mount it properly today.