I have a 2004 Monte Carlo super sport supercharged push rod V6 engine. I've never had any problems with it until now. On my way home from work that's on pulling up to a stop sign the car died. I put it in park try to start it with no luck. I still have power all the lights were on everything still worked it just wouldn't start. Can somebody please tell me what would cause this. I need this car to provide for my family. Please help
THANK YOU

 

Is the starter turning it over, but it just isn't firing or is does nothing happen at all with the engine when you turn the key?

 

It's turning over it just ain't firing up.

 

Ok, so that means it lost fuel or spark. What is the fuel pressure reading? Have you tested for spark?

 

My car had no spark I've changed all plugs and all wires but still no spark what else could cause that?

 

IMO plugs and wires were a waste of money. Neither would cause absolutely zero spark.

Id check the ICM next. A failed coil pack could do that too, but no way all 3 coil packs would die at the same time. A dead ICM could wipe out all 3 at once though.

 

Sorry I'm not no super mechanic. What's the ICM, is that the thing that the three coil packs are both in on top of? If so how would I check if it's blown?

 

Correct, its the flat box that sits under the coil packs. They seem to be getting more and more common to fail as these cars get older.

Do you have a multimeter? Id check first to see if its getting power + ground at its harness. Maybe you get lucky and a wire popped loose somewhere / got damaged. Then Id proceed to check the other inputs. If its getting everything it should but isn't outputting anything, then it would be a safe bet to swap another one in.

 

A bit more detail on icm testing:

• Check for input power. Typically pink or pink black, all the way on one end of the harness. Check this for 12v (with the vehicle ignition on) with the ground wire on the battery -. If good, then move to next step.
• Check for ground circuit connection. If we call the 12v wire above wire #1, ground will be wire #5 going across the pack. Usually black or black with white stripe. Either check this for ohms/continuity to the battery negative, or check for 12 volts relative to battery positive.
• Check sensor power out from the ICM. The ICM runs off of engine position sensors, but it won't spark if it doesn't see signal back from them. The power to those sensors passes thru the ICM, so if this connection breaks internally - no power goes out to the sensors and thus the ICM doesn't see a signal back. This would be wire #2, right next to the wire in step 1 (white black stipe usually). Check for 12 volts with ignition on relative to the battery negative terminal.
• If thats all good, we need to see if crank signal is coming back. This wire #8 using our numbering scheme (its the first wire after the center bolt) - generally yellow or yellow w/ white. Youll be checking for signal voltage - about 6v. Again with ignition on relative to the battery negative. Youll want to connect these probes, then turn the engine over by manual tool (breaker bar on crankshaft). As you turn it, you should see the it jump between 0 and 6V often (its 18x, so you shouldn't need to turn the engine over much to see it pulsing).
• Lastly is checking cam signal. This is wire #7 in this numbering scheme - the last one before the center bolt on the side you started on. Likely blue, light blue, or one of the above with white stripe. Its checked exactly like crank signal. Looking for 6v power (relative to battery ground) pulsed as the engine is manually turned. But this is only a 3x signal, so you'll see much less pulsing from 0 to +6 as you turn.

If all of that checks out and the ICM still isn't putting out any voltage to the top terminals/coil packa, then the ICM has failed inside. Its getting all of the info it needs to produce spark, but some connection is broken inside / not allowing that to happen.

Take the wire colors with a grain of salt - there were some differences looking through the wire diagrams of the various 3800 books I have. Positions are correct, but wire coloring may vary model to model.

 

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