2004 Pontiac Grand Am GT, 3.4L V6…It only starts if the battery has been disconnected for at least an hour and then is immediately reconnected prior to use. Once the block is hot, however, it starts flawlessly and repeatedly every time. When the block cools, it won’t start again unless I disconnect the battery and wait an hour.
I did a bunch of tests without first disconnecting the battery: The fuel bar is pressurizing properly, the crankshaft position sensor works, the ignition control module has power, the plugs and wires are in good condition and have the right resistance. The coils are fine. I did an OBD-II scan as well, no codes. However, unless I go through the disconnect-wait-reconnect procedure, there appears to be only a weak spark.
I don’t think it’s the ignition security feature. There’s no security light, performing a security reset does not fix anything, and the car starts repeatedly and reliably as long as the block is hot.
I was wondering if it might be a failing sensor that has a thermal dependence? Should I look at the powertrain control module? The ignition control module?
Thanks!
Does the vehicle crank but no start? If so, have you checked your ground connections for the ECM or engine to chassis grounds? To test if it is an engine to chassis ground, you can install jumper cables from a known good ground on the engine to a known good ground on the chassis. Engine speed sensors sometimes have excessive resistance when the engine is hot, not allowing a start but the vehicle will still crank. Please add more info
The engine cranks fine whether the block is cold or hot. I checked the grounds. They are fine, as well.
The engine starts and runs perfectly fine when the block is hot.
The problem is that the engine won’t start when the block is cold unless the battery is first disconnected for at least an hour, then reconnected.
On fuel - its not enough to know that there is fuel at the rail. You need to know what the pressure is. You also want to find out whether the injectors are actually firing.
On spark, basic checks are good, but the real check is whether you actually have spark - have you pulled a plug & actually looked?
You said the CkPS “works” - but that could mean a lot of things. It works in what way? When and how? Or, in other words, how & under what conditions did you check it?
On fuel: I did measure the pressure in the fuel rail with a pressure gauge. It is within the nominal range.
On Spark: I pulled the plugs. The spark is no good when the car is cranked cold, which I assume is the reason the vehicle won’t start. However, if I disconnect the battery, wait an hour, and reconnect the battery, that symptom goes away and the vehicle starts on the first try. It then runs normally, and will continue to restart reliably without fail, so long as the block remains hot.
As a result, I know that the injectors and ignition system (plugs, coils, ICM, CkPS, etc.) work properly under the following conditions: 1. The block is hot, 2. The block is cold, but the battery has just been reconnected after a wait of at least one hour.
This leads me to think that the actual problem is with either the PCM or ICM, or a sensor (not the CkPS, however) that is causing the PCM or ICM not to provide the proper signals to run the engine (i.e. spark timing signals and injector firing signals). I would guess that the former has a volatile memory component that is reset once the local hold-up capacitor dips below the refresh voltage. Therefore, when the system is reconnected, the PCM runs through vehicle start-up from a different state than it would following a run and cooling cycle without a battery disconnection. Perhaps, one that does not poll a failed sensor. In and of itself, this does not mean that the PCM or ICM is the problem, rather more likely it’s a sensor problem. But I really don’t know where to look short of replacing the PCM or ICM. If there’s a sensor that could be a likely culprit, I would prefer to try that first.
Is there any sensor that the PCM or ICM looks at when it determines whether the vehicle should be allowed to start, but would ignore on the very first start of the vehicle after the battery was disconnected for an extended period?
I have a very similar problem on a 2002 Grand Prix 3.1 liter. I get spark good fuel pressure and it will fire if I spray fluid into the intake. Apparently no injector pulse. If I remove the ECM fuse or disconnect the battery an hour when I reconnect it starts. If I let it warm up it will restart until I let it cool down at which I am back to the intitial problem. I have replaced both crank sensors and the ECM.
This is a strange problem. From what you state about the trouble it sounds like a memory has to be cleared before the injector circuit will work. The ECU is the only thing I can think of that would fit that senario and you have already replaced it with no help to the problem. The only other thing I can think of that may be a possible problem is a faulty diode in the circuit may be breaking down but that is a real wild guess.
Since you say removing the ECM fuse for an hour clears the trouble it may help to monitor the current through that fuse to see if there is a change in current flow from when the car is shut off and when it has cooled down an the trouble occurs. To do that you can replace the fuse with a meter set to read DC current. I would have the factory wiring print and check everything that is tied to the ECM fuse circuit that could possibly influence the problem. It may also be a good idea to clean the engine and chassis ground connections under the hood. It may not help but it sure can’t hurt to do that.
SAGNEA!!!
I made an account just to reply to you!!
My 2004 Pontiac grand am v6 is doing the very same exact thing, to the T! The very same exact thing! Please please tell me you found a solution for this problem.
[edited to remove email address -carolyn]
I think Elvis has left the building after 5 years.
I’m the OP (I had to create a new account because the lost password function refuses to recognize my email address…or I forgot which one I used). It has been 5-ish years and that car was totaled after I lent it to a friend about a year after my original post. That said, I do have some additional information, if not particularly satisfying from a diagnostic perspective.
About a month or so after my original post I ran over a (already dead!) deer on the highway in the middle of the night. The deer was laying feet-facing-me across the middle lane and I had nowhere to go but up and over when it became evident something was in the road. So I held onto the wheel and launched right over the top at 75MPH. The landing was quite a jolt, but the car was fine…no body damage or obvious mechanical damage of any kind (which is more than I can say for the guy behind me that tried to swerve and avoid the carcass and precipitated a minor pile up).
In fact, it was better than fine. From then on it worked perfectly (as in started without fail, no need to disconnect the battery and wait) until the day it was totaled.
My best guess at this point is that the problem was related to an intermittent ground return (as some have suggested). This would be consistent with both the temperature dependence - assuming thermal expansion of something or other was closing the connection when the block was hot - and the fact that after I knocked the heck out of the vehicle it worked normally - assuming said knocking resulted in permanently closing the intermittent connection.
An intermittent ground is also consistent with the reality that opening a return path in a multi-return system often leads to unintended behaviors as current returns through sneak paths in the various bits of silicon comprising the system (e.g., a pin now floating halfway between logic rails in digital no-man’s-land wreaking havoc on some poor subroutine).
Unfortunately, since the problem resolved itself, and I’m not one to look a gift horse (deer?) in the mouth, I didn’t root cause the issue. I’d start with checking all the grounds (under some sort of load…I did do it with a DMM) in the system related to the PCM and ICM and then branch out from there.
Well welcome back. If anyone needs a dead deer to repair their car with, there are plenty on the road around here. Must have been a wild ride. Always better to hit a live one than a dead one for insurance purposes.
First step is to determine if the no-start problem is due to spark or fuel.
blockquote, div.yahoo_quoted { margin-left: 0 !important; border-left:1px #715FFA solid !important; padding-left:1ex !important; background-color:white !important; } Okay. I’m out of state working. It’ll be Tuesday before I can look at it
Yeah, it was pretty embarrassing to hit an already dead deer. That said, there was pretty much nowhere to go!
@GeorgeSanJose: Is there a differential diagnosis wrt fuel vs. spark? By that, I mean does the absence of one vs. the other point you at a specific module (e.g., spark being more likely the ICM)? At the time, I was working off the factory manual, and while there is plenty of useful information there, it doesn’t provide details about the contents of the module or even a state-machine diagram that could help with the detailed relationships among modules.
In my case, the fuel rail was pressurized etc., but there was no spark (and possibly the injectors were not firing) until one of two conditions were met: 1)the battery had just been re-connected after a 1-hour or greater disconnect, or 2)the engine block was already hot. Once this happened the car ran completely normally: same fuel economy, same available power, no knocking, etc. That led me to believe that the effect was limited to one of the modules, but secondary effects on a module due to a ground issue makes a lot of sense to me now, post deer.
Spark is usually the easier to check. I just put a spare plug on one of the spark plug wires , hold it against an engine ground, and have someone crank the engine. The spark is easily visible at the electrodes, if present. It should be bright and white/bluish in color. There’s no point in considering other no-start possibilities until that has been done.
In your case there was no spark, so that’s where you’d start. The engine will never start if there’s no spark. In your case the question is : why is there no spark? For that you’d have to go to the factory service manual to determine what criterea are required to produce a spark. It varies car to car. On my Corolla they are
- Ignition switch in “start” or “run”
- At least 12 volt power at the ignition module
- Engine computer has determined crankshaft is turning (in my case it uses a distributor cam sensor)
- Certain hardware must be functional, e.g. igniter, coil, engine computer, wiring harness
If I had a no-spark I’d start with the first three, make sure those are working. If I still couldn’t figure out the cause, I’d bring out my lab oscilloscope next. There are 3 or 4 test points provided by Corolla engineers, that would show me if the basic timing signals were being generated.
If they were sometimes and not other times (as in your case) and no obvious reason for that after doing the above, I’d remove the distributor, which contains the ignition module and igniter, and have a good look see of that on a brightly lit work bench using a magnifying glass. Next I’d remove the engine computer and do the same with it, looking for cracks in the circuit board or in the surface wiring traces, discolored resistors or capacitors, etc. If I still found no obvious cause I’d next re-install the distributor and engine computer & start probing the engine computer circuit board with the o’scope .
I hit a raccoon one night and he was just high enough to take out the radiator support and the air dam for $700. My agent wanted to know if it was alive or dead. I said it was alive before I hit it and dead afterwards. They paid everything.
blockquote, div.yahoo_quoted { margin-left: 0 !important; border-left:1px #715FFA solid !important; padding-left:1ex !important; background-color:white !important; } Okay so I have determined it’s getting spark. When in morning time and before I took the battery off for the first an only time of the day, attempted to start again, no go. So first pulled the spark plug wire off from the coil pack and the coil pack plug(looks just like the top of a spark plug) it was definitely sparking. Put battery back on, starts runs fine for remainder of day.
So, it’s the car not allowing fuel through the injectors still I reset the battery( for 30m each morning)
Anything, anyone, suggestions or helpful hints or ideas to move to the souloution or finding out what it may be
I know very little about cars but my 2004 grand am has been doing the exact same thing! Starts on first try as long as the engine bay is still warm. Even just a little bit of heat is enough. As soon as it’s cold it won’t start unless the battery was promptly disconnected after last use. If I let it go too long without disconnecting battery after driving it and it cools all the way down it can take several hours of being disconnected before it starts again. It’s very perplexing and quite inconvenient! Fortunately my bf installed a key to connect/disconnect the battery easily. Has anyone figured this out yet??
Suggest to post your problem in its own thread @Heimarly , you’ll get better results here. Heat related no-starts but cranks ok are often caused by a failing crank position sensor. Usually though the symptom is the reverse of what you say, it won’t start when the engine is hot, but starts ok when cold. But a failing CKP sensor could cause your symptom too.