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Hi everyone, so here is my issue, 2003 impala 3.8, I swapped the transmission and it started right up no problem and ran great. This was without a radiator in though as mine was cracked and was awaiting delivery of its replacement. So the new radiator came and I installed it and when doing this I had to take out the battery and the air box which also houses the PCM. Put it all back together and now when I turn the key all that happens is the check engine light illuminates. Nothing else works. I have 12v over all the fuses and a fully charged battery. And I know the PCM is getting power because when I pill the PCM fuse the check engine light goes out. the car does not have power at the obd even. Really strange I’m not sure if this is a bad PCM possibly or passlock issue and I’ve checked the PCM connections 100 times now and are 100% secure.
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well I have been using the engine block and transmission as grounds when im testing the fuses and so I know that the ground on the block is good because there is only one, There are also two body grounds on each side of the engine bay I have not checked those but did take them off and put them back on when I swapped the tyranny a week ago. I will try cleaning them up and seeing what happens. Thanks.
Ok so I went and cleaned all of the body grounds and its still doing the same thing. I did notice that either the IAC valve on the throttle body or the TPS is making some clicking noises. I also took the cover off of the PCM to see if I could see and shorts or anything but I didnt see anything.
You might double check the battery and it’s connections. If you don’t have good connections there it will effect all other electrical systems on the vehicle. More info here.
http://www.ericthecarguy.com/faq/solving-automotive-no-start-problems
http://www.ericthecarguy.com/faq/solving-automotive-electrical-problems
Good luck and keep us posted.
Thanks for your response Eric! Well I decided I would order a PCM for it because I could get one that was programmed to the vehicle for $70 and the PCM has good power and ground running to it, but it has no functionality whatsoever. I blame this possible failure on the fact that the ignition went bad recently and was replaced, however I think that the ignition sent voltage spikes to the PCM which damaged it, and maybe when I removed to change the radiator it pushed it to failure. I am also thinking it was on its way out because recently I noticed when you turn the key it takes it a second to respond as if its running slow. I will definitely post again once I get the new PCM installed and see if that solves the issue.
That’s an awful lot of assumptions. Aside from that, I don’t believe the PCM has anything to do with a no crank no start on that vehicle. That said, keep us posted on your progress.
Ok so I installed the new PCM and it is still doing absolutely nothing but turning the check engine light on. Im getting frustrated being that I cant find any diagrams for this car either. Im thinking about just getting a different harness from the junk yard and seeing if that will do it, I just dont see how I damaged any electrical by putting the radiator in.
So I went back out to the car and found something interesting, all of the fuses on the dash panel of the car have .64 volts to them except for the PCM crank fuse. it has 11.57. I also found that the radio fuse was blown which I thought was possibly the problem since the radio is a part of the passlock system, but I replaced it and nothing changed, but why was it blown in the first place? because the radio was working before I put the radiator in. I would think that those fuses should have more than .64 volts in the ACC position, there has to be a fault in the wiring somewhere.and in the underhood fuse block there are 6 fuses right next to eachother that have no power, one of these is “engine devices”.
[quote=”EricTheCarGuy” post=105552]I don’t believe the PCM has anything to do with a no crank no start on that vehicle.[/quote]
On these GM passlock vehicles like the Impala and Monte carlo the BCM checks the passlock circuit and gives the ok to start to the PCM which will enable the fuel delivery and crank circuits. So it’s involved but not the first thing I’d jump to.13aceofspades13 has a lot of the pattern failures for these cars here: http://ericthecarguy.com/kunena/common-problems-pattern-failures/50806-gm-w-body-cars-3100-3400-sfi-3800-engines
My $0.02 I’d check the connection between the battery negative and the cable that side post screws into it if that has a somewhat flakey ground it’ll cause gremlins.
The radio isn’t really involved with passlock. The OEM radios check security over the class2 data line and go into locked mode if the BCM is changed or if it’s not programmed for the car.
I’ll definitely check the battery cables, I just think its strange that some of the fuses have 12v across them and others have less than 1v. Thanks for the info!
Well good news! I got the car running today, turned out to be just a bad ground, not sure how I overlooked that one, but now at least I’ve set a good example why you shouldn’t throw parts at something. Thanks Everyone for your input!
We’ve all done it Durango… Thanks to Eric and experienced folks sharing knowledge on forums like this, we DIYers can learn and keep money in the pocket. You probably would have spent more money by driving through the door of the dealership. Great find and good job man.
Glad you got it resolved. Which ground connection was it? Just curious and it might come in handy to others in the future.
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