Thread: 2008 Grand Prix Base 3800 - Tries to turn over, no spark

08 Grand Prix, 3.8l Series III V6, around 206,000mi on the clock.

Here's what I'm encountering, I'm hoping someone here can point me in the right direction as I've searched all over the internet and tried everything I've found and can think of, and gotten nowhere. Around March/April of last year, I noticed the car running pretty poorly, so we changed the plugs and wires. Then the alternator and starter decided to die at the same time a few weeks later. Got that cleared up, then parked it to take a ride from GA to CT in our other vehicles. We came back home, it started a few times, but would just...die. Managed to move it from one side of the yard to the other in Late July/August, and haven't been able to start it since. At first it wouldn't even try to crank, so I figured it was time for a new crank sensor. Changed that, and the cam sensor, and now it'll try to crank, but no fire. Took a look at the ignition wires, and it turns out they were defective, so we got them replaced. No progress. Figured it might be the coils, changed them, no progress. Finally pulled the plugs out, and they all had one weird burn mark in the exact same spot, so we got them replaced. New ignition module to be safe. Checked all the fuses, relays, none were broken, but replaced a couple nasty looking fuses anyway. Still nothing. Even changed out the wiring harness that plugs into the ignition module. Still nothing. Throughout all this we've also replaced both batteries cables with ACDelco factory replacement cables. The car still will not start, but everything else is working as normal. Found a video with the same issue, the guy tightened the grounding bolts in the fuse box and it worked, so we tried that. Still nothing. Any insight or help in this matter would be exceedingly appreciated.

List of new parts for reference: New alternator, starter, battery cables, ICM connector, ACDelco plugs, new coils, new wires, new ignition module, new crank and cam sensors.
Battery is fairly new, and I don't believe that's the cause of the issue. We've tested spark, and we get nothing from testing the wire, and nothing from testing the plugs against a ground. Just no fire whatsoever.

Do you have a second key to try with? Maybe the anti-theft is kicking in. I don't remember what it shuts down tho. Maybe the ECM decided to die? Are there any OBD codes present?

We've tried the factory key as well, no luck. There's an APP code, and an ABS code, but I can't imagine either of those would prevent spark.

It actually needed all of those parts regardless of the current issue, I bought it in terrible condition and no work had ever been done to it. I have a live data scanner, but I don't know if it shows those pulses. Might be the next thing I have to try.

Originally Posted by BillBoost37

What's an APP code?

And.. where in GA are you?

Accelerator Pedal Position Sensor.... Which has been replaced 3 times.

And I'm in Calhoun

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Originally Posted by BillBoost37

I'll assume you checked the wiring to it, but if not it sounds like a starting point. Odd that you can have that many go bad.

I'm in Savannah. I'd offer to help, but that's an all day drive.

One is new, one is factory, one is from the junkyard. When I first got the new one, the code went away for a while. I did some research into it, as the code is actually "Accelerator Pedal Position Sensor System" which includes the throttle body and a few other things, hence the changing of so many parts on that side of the car. The other one I have is for the steering angle sensor, which I am dreading changing, but I can't imagine either will cause a no-spark/no-start. I've also been trying to figure out why I have that damn "reduced engine power message" that won't go away. But I know the first thing I need to do is be able to actually drive it so I can reset whatever codes may no longer be relevant.

Did you use an ACdelco ICM? I have had issues with others that went away when I went to a delco one.

Did you do a crank relearn with a tech 2 after all the parts replacements?

Just brainstorming.


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Originally Posted by markpa

Did you use an ACdelco ICM? I have had issues with others that went away when I went to a delco one.

Did you do a crank relearn with a tech 2 after all the parts replacements?

Just brainstorming.


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I don't have access to a tech II but I did have access to a Solus 2 that I used for the throttle and APP relearn. It hasn't started since before I changed the crank sensor, so I'm not really sure how I would reprogram that as it wants the crank to be spinning to learn the position with the scanner I used.

Couple things... you can reset codes without it running, and it should (if there are any continuously monitored faults) return the issues immediately. If you're getting a reduced engine power message with just key on, engine off then there is a present issue in engine control. That does leave a lot of possibilities, and this is where your live data comes in.

You have a SOLUS? That will give you and parameter you want. Check for crank position signal while cranking, if you have that you can move on to why it's not sparking. it won't read high, probably 200rpm at most, but it's just a signal check.

I'd do a full vehicle code clear, and check what comes back. Your codes will give you an idea.

If you have an APP fault, and access to a multimeter make sure you check for a 5v signal supply. i don't have wiring diagrams, but any electronic throttle body has to have a reference voltage. This could also be seen on your live data, and would trigger a reduced power message.

i don't know if any of that is going to make sense or be helpful, but i figured i'd throw in my input.

I no longer have access to the Solus, I was borrowing from a client when I worked at Advance Auto

Without proper diagnostic tools, it's going to be incredibly difficult to diagnose an issue like this, and you'll likely end up throwing a bunch of parts and money at it unnecessarily.

You might want to weigh the costs of either buying your own from somewhere like harbor freight for a much more reasonable price than a tool truck, or paying someone with the tools to diagnose the car.

Originally Posted by onxy

Without proper diagnostic tools, it's going to be incredibly difficult to diagnose an issue like this, and you'll likely end up throwing a bunch of parts and money at it unnecessarily.

You might want to weigh the costs of either buying your own from somewhere like harbor freight for a much more reasonable price than a tool truck, or paying someone with the tools to diagnose the car.

I'm kind of okay with throwing new parts at it when I can, because it desperately needs it, but I am planning on asking someone to come look at it soon.

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Hello I have a 2007 Grand Prix GXP doing the same thing yours doing turning over but not starting due to no spark…. Did you ever figure this problem out…?…. I’ve changed everything including the sensors the next thing I’m thinking about changing is the PCM….