The door unlocking and the instrument cluster warning lights illuminating after the engine had already stalled out are perfectly normal for this vehicle. I am not at all surprised that there are no trouble codes stored in the PCM.

My *guess* would be a temporary loss of crank sensor signal but there are LOTS of other possibilities. Pinpointing the exact cause of such an intermittent problem requires patience and proper skills/equipment. But in my book, that still beats the heck out of just blindly throwing parts at it.

When you say the car has been "slow to start", do you mean that it has been hard to CRANK (engine slow or hard to turn over) or hard to START (engine turns over fine but takes several revolutions to start)???

-Mark

Hi Bucky

When I'm in the shop sometimes the customers think that I ask too many questions. Often times they don't understand how something that to them is an obscure piece of information can make the diagnostics much easier for me.

Lets look at the facts as you gave them here. The car quit on the highway, OK lot's of potential reasons for that. Then once it was stopped it restarted relatively easily. Ok same thing, there are a lot of possible causes. HOWEVER, the doors unlocked. For me that is a glaring piece of information. Think about that for a minute, the doors unlocked. When you get in the car and start it up, the doors don't lock until you put it into gear, and/or start moving. Then unless you hit the door button and unlock them, they don't unlock themselves until you, what??????

Turn the car off.

No question, you lost power on the circuit that the BCM monitors as an ignition switch turn on/off, and the BCM did what it was supposed to do "If you had turned the engine off", and that is it unlocked the doors. That's why there is no code stored as well, turning the car off won't set a code. Now the most likely suspects are: The ignition switch, a power distribution center fault, or of course some type of wiring harness trouble. However the fact that the car restarted with little trouble just screams ignition switch. This should be easy to verify by driving the car with a volt meter connected to the correct fuse in the fuse block and watching for a system voltage drop to start to occur. Remember though, test, don't guess. Plus be advised, you cannot replace this part yourself because of the way the PasslockII system operates. In fact only a shop, or a dealership with ESI software and a TechII can perform the relearn that is required to reset the theft deterrent system after the ignition switch is replaced.

Hey Semper Fi. I've seen your responses on a couple other posts, nice job from not only another Marine, but another ASE CMAT, with L1.

On this one, a 2003 Malibu, if he lost the crank signal it would definately set a code because it would still get some cam signal pulses. Besides it has more than one crankshaft sensor, so it might not even quit running with a bad crank sensor. The slow to start that bucky mentioned would be something I would treat as a completely different failure, virtually as if it was occuring on a different car.

John,

First and foremost, Semper Fi marine! I just read your credentials on your page.... VERY impressive.

Just a few weeks ago I did a diagnostic on a late model 3.1L GM with a very intermittent stalling problem. No codes would set and the vehicle would restart just fine. After MUCH driving (200+ miles) and MUCH scoping, I found that the 7x crank signal would drop out for a split second and the vehicle would stall. I think I still have a nice movie of the entire event on my trusty Interro 4-channel scope. So why didn't it set a code? As you well know, when those whacky engineers write the code for the PCM software, they often leave a small window for error to lower the possibility of false codes. My *GUESS* is that the signal loss happened so randomly & quickly that it just barely fell under PCM's radar. You are absolutely correct that if the other (24x) crank sensor had failed, it wouldn't have caused the same symptoms.

I also agree that it could very well be a faulty ignition switch as they have tons of problems with these. The only way to really know for sure is for Bucky to have a competent shop duplicate and diagnose the problem.

I need to update that page, sheesh it's been a while since I looked at it.

200 miles give or take to duplicate and diagnose a problem. The average consumer has no idea what we do to try and keep their cars on the road. I just worked with a tranny shop, helping them out with an EPC issue on a Continental that they had overhauled the tranny on. Time and again, I can have multiple unbilled hours into trying to catch random failures to allow them to be diagnosed and stop the parts throwing that often goes on. I probably had five hours of unbillable time into that one. In the end, it did have a bad PCM, but they had built an intermittent open into the tranny as they shotgunned parts at it in their early attempts to fix it. Two problems, one they self inflicted.

So are you a member of the iATN?

Something I need to add to my page will be I added a "4th job" I am a trainer in traing for CTI, Carquest Technical Institute and will soon be out there passing on what I can to other shops/techs. I'm hoping this will be how I retire, since wrenching is getting to expensive to try and keep up to date as a one man show, and the body simply has it limits and my age is showing more and more as I do the heavy stuff.

Good Day Semper_fi and John G. Thank you for the feed-back on my post. To clarify...the car has been "hard" to start. Turns over fine but slow to start. Refuses to start on the first try but so far has started on the second try. Interesting to learn that the ignition switch is a glitchy part on this vehicle. Its no Lexus but has been relatively trouble free, other than front rotor wear, since we got the car in 03. I had the dealership check for codes but no code was set with the one stall failure we've encountered so far. I sure do appreciate the "education" you guys provide to me and the members of this list. Cheers: Bucky (Not an ex Marine, just an old Jet Jock)

I know those unbillable hours very well John since about 60% of my work is doing electrical/diagnostic work for other shops. Isn't a shame that doing tough driveability work is so rewarding in so many other ways (solving puzzles, helping others, figuring out what other can't or don't want to, etc.) than to the shop's bottom line especially in a one man operation like ours?!

I am an iATN sponsor. I joined the network about 10 years ago when they had less than 5K members. Look at it now! It's an incredible resource for our industry! These days I rarely visit the off-topic forums because I had a disagreement with the way the powers that be delete most pro-military discussions but allow the anti-troops sentiments expressed by a few stand. I felt it was a slap in the face of fellow members who have served especially those who have kids currently serving. But hey, it's their party and I'm just a guest. Fortunately, the network's pluses far out outweigh that one minus.

So what is YOUR favorite way of testing EPC circuits? Current ramping and watching for a "kick"? I really enjoy studying the approach and tactics of the Top Guns in our industry.

My apologies to the Ole' Jet Jock for taking this slightly off-topic! :-)

semper_fi: No apologies are in order young fella. I'll "Roger" that!!

Fellas: My lovely wife's 03 Malibu has "shut down" on 3 more occassions in the past 4 days so I took it into my mechanic again today. Still no trouble codes on the obc. Any suggestions on a course of action on this? My mechanic says just keep driving it until a code loads. The car is basically not driveable due to its lack of reliability. She's traded cars with me and is driving my Riv. This is not good as I wasn't that fond of the Malibu when it was running okay. :-) Bucky

When your heap is running grab the key and jiggle it all around and/or pull down on it - see if that makes it quit. Lift up and see if it keeps going.

I had a Honda the previous owner hung a 5 pound ball of keys from the switch. Any wonder it failed? I hooked an elastic cord from the key to the visor to pull up on it till I had time to install a new switch.

-Ye Olde Shadetree

Problem was finally diagnosed as a faulty crankshaft sensor. Intermitent failure that for some reason would not set a trouble code. Apparently these Chevy's are notorious for early crank sensor failure. Running like a top now. Thanks to all who responded to my post. Bucky

IMHO, it's great and very helpful when people actually take the time to add a follow up to their origianl post. Thanks for posting the FIX on this, ye ole' Jet Jock! :-)

Well dag nabit anyway!! Thought the darn thing was fixed. Car ran ok for about 5 days and crapped out (stalled) again today but fortunately this time on a side road. Guess the crank sensor was not the problem or another has developed. Well back to the shop on Thursday fellas.

Did the doors unlock again when it quit?

If so go back and read my original post. I can't tell you how many times I get cars into the shop that have had three and four parts thrown at them, that have random issues like this. This is the most difficult work that a technician ever has to do, and it is also the least profitable.

The questions now are, was the crank sensor bad? I don't know, and I have no way to tell. It might have been. How long will it take for this problem to show up again? Another five days, a week, or two weeks ? How long is the car dead when it acts up? This might only be diagnosable in the period of time between the engine stalling, and it's restarting.

Hey John G. Thanks for picking up this thread again. The car doors did unlock again and all power was lost to the vehicle for a brief period of time. Dash lights shut off briefly when the engine quit and then came back on. On the last occurence the car started again with no problem. I did mention to the mechanic that I'd received a suggestion to have a close look at the ignition switch and was surprised when he said it was a bad crank sensor. Seemed to me that a bad sensor would not result in a total elec shut down of the vehicle but should set a trouble code. On the positive side, I have just found out that the POWER CONTROL MODULES are still under warranty (8 years or 100,000miles) so if its determined that its one of these babies at least its covered by GM. I think that all will agree with you that intermitent electrical glitches are the most difficult and challenging problems to diagnose. Thanks for the reply. Much appreciated

"Dash lights shut off briefly when the engine quit and then came back on."

Aha! Bucky, was this symptom there during previous incidents? If so, did you tell them that important piece of information? That sure sounds like faulty contacts inside the ignition switch.

semper fi: Yes I told the mechanic that on the initial repair visit. In fact I wrote all of the details down on paper for them. The car is with the mechanic again today and I reminded him of the no dash lights symptom. I also informed him, on the first visit, that it had been suggested to me by knowledgeable people that it could be the ignition switch. Also today on the second go. Thanks for the reply semp. Bucky

If the switch doesn't turn out to be the issue, you might want to look up "fretting +electrical contact" in your favorite search engine.
For some intermittent issues I've had success pulling all the critical connectors, spraying them out with a product called Nu-trol from MG, and working the connectors back and forth a few times.

Sounds like an internal problem like a loose connection in the CPU. Won't set any codes when the diagnosis machine is hooked up. Try that first before going to a shop that won't know the problem anyway, but will surely charge $90/hour to confirm they don't!

Chad. Your response is neither helpful, nor correct. I looked at your page, and see that you are new here.

First, a good shop "does not know" what is wrong with the car. They have to get it to act up, and TEST during the event to find out. Even in this case, where the details have given me a strong insight into exactly what happened, I do not condemn a part based on that alone.

I do this kind of work day in and day out. I know exactly how I would test this car for this problem, which BTW the testing itself would likely take me under half of an hour of time. The problem is, it may take a week or two of "normal use of the car" to get that half of an hour window of time that the car is broken in which to do the testing. There is no more difficult work that an auto technician has to perform. It takes special people, with extensive training to do this kind of work, and they darn sure should be paid well to do it. Your post suggests that the efforts required to do that have no value. That is wrong!

There is no magic machine that diagnoses a car. Diagnostics are performed by the technician, using the correct tools. A scan tool, not to be confused with a generic code puller that a parts store uses, can do a lot of things and display a lot of data easily for a technician to monitor. But it does not, cannot, diagnose. Diagnostics is not pull a code and slam a part, as some parts store people might imply.

Before you throw out "guesses", and in the same breath take a shot at my profession. Open a service manual, particularly a schematic and look at it. Then come back here and explain to us EXACTLY how a loose connection "in the CPU" can cause the car to stall, AND the dash lights to go out, AND the doors to unlock. Tell us the wiring pin ID's that would be affected by this "loose connection". Tell us which "CPU" inside of which module is capable of causing this problem. (That's right, in this car there are dozens of CPU's spread through quite a number of modules, so pick ONE!)

"Sounds like an internal problem like a loose connection in the CPU."

LOL! Yeah Bucky, and if the "CPU" thing doesn't turn out to be the culprit, try closing all the windows and rebooting the car. ;-)

Looks like our resident GURU nailed the correct diagnosis of the problem right off the get go! John G.....looks like you've done it again. Replaced the ignition switch. Car has run fine for 5 days now with no sign of the stalling problem. Got my fingers crossed but I think the thing is fixed.
Also thanks to Semper fi. You and John G. are the best. Bucky

Nah, I'm an overzealous mechanic on a quest to look superior.......

That's why I spend so much of my time studying, and why I spent this evening at yet another school, with one little twist. Tonight I was the one in front of the class, instructing my peers on just how to grab those little pieces of information, like your doors unlocking. I'll be doing it again tomorrow, for the second four hours of this months class.

Anyway Bucky, your welcome. But this seems to mimic how my days really go. I don't get to sell entire fuel systems, for a restricted filter. Sometimes it feels my experience and knowledge are worth exactly what I got for diagnosing this for you. I get to deal with people like Chad. I wonder what bill I can pay with that???

Thanks again Bucky for posting the FIX.

John, what is the subject of the class you are teaching? Basic Driveability or???

Powerstroke 7.3 diesel. Basic class.