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04 ext Shuts off randomly.

9K views 38 replies 4 participants last post by  the cadillac man 
#1 · (Edited)
About 2 weeks ago while driving my ext the traction control light came on saying service stability system and the the truck would go into reduced power mode. I did a lot of research on the subject and it seemed that the most likely cause was either a bad throttle position sensor or a bad pedal position sensor. Before replacing either sensor I carefully inspected the wiring coming off of the Tps. Everything looked good and I ended up replacing both the APS and the entire throttle body. During the process my battery had died I had tested the battery before I changed the other parts and I was reading 12v with the truck off and 14v with the truck running with High beams on and AC on full blast. After the battery dropped below 9v (an optima yellow top) I attempted to recharge the battery but the voltage refused to increase.

I purchased a new battery and the truck drove fine for a couple of days. Then one day while driving every time I would hit a bump in the road my doors would unlock and then lock again plus the gas pedal wouldn't respond for maybe 5 seconds and then everything would work again. Finally I hit a bump and the truck shut off completely. The navigation and dash lights all worked but the engine was off and pulling over to the shoulder the truck wouldn't start any more the engine wouldn't even crank nothing happened at all when I i turned the key but the electronics would come on.

I got the truck towed home and noticed that one of the bulbs in each headlight were on and would nit turn off. I think it's a blinker bulb the top left bulb if your looking at the driver side headlight head on and the same one on the passenger side but that one is top right. So I disconnected the battery.

I havnt been able to pull any codes from the truck because every time I try my scanner says unable to communicate with vehicle. I was previously able to to get my scanner to communicate with the vehicle which is when I changed the TPS sensor but after the truck continued to go into reduced power mode I tried using my scanner again but it wouldnt work that is when I changed the TB and Battery. I made sure to check my cigarette lighter fuse as its the same fuse used to power the obd2 system and it was good. While talking with a friend he suggested I may have a bad ECM I checked online and found I could get a working used ECM flashed to my vin for $100 I'm going to give that a shot when u get home.

I was wondering if anyone had any ideas what the problem may be just in case it isn't my Ecm. I've also tested all of the relays in the fuse box under the hood and even tested my ground wires at the frame and engine block which all test as good.
 
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#2 ·
UPDATE... Replaced ECM and nothing changed. My scanner is still unable to communicate with the vehicle I hear nothing when I turn the key to start the truck. The security light (picture of a car with a lock on the dash) is stuck on and the I still have the one bulb in each headlight on non of which will turn off unless I disconnect the battery.
 
#3 ·
Bigrick31 said:
UPDATE... Replaced ECM and nothing changed. My scanner is still unable to communicate with the vehicle I hear nothing when I turn the key to start the truck. The security light (picture of a car with a lock on the dash) is stuck on and the I still have the one bulb in each headlight on non of which will turn off unless I disconnect the battery.
I wonder if it is the bcm going bad(it works the lights and security system)
 
#5 ·
Bigrick31 said:
is there any way to test the BCM before going to the dealer for a new one? Do you think theres any chance its the ignition switch or the passlock system?
Well is anything else in the truck acting up (the bcm works everything in the truck
Lights(interior and exterior)
Locks
Both front door modules(door switches)
Wipers(front and rear)
Radio and amp(including the cd changer 03+)
Gauges
Seats(both memory and seat controls via seat module)
Locks
Keyless entry
Onstar system
Rear seat entertainment system
Pass lock system/anti theft system
And recives data and sends data from and to the PCM via the class-2 data bus

If multiple things in the list is acting up then most likely the bcm is the cuplrit
 
#6 · (Edited)
Everything works as it should in the vehicle the only time then door locks or headlights give me trouble is randomly when I hit a bump in the road which will cause the truck to either shut off completely or go through a 5 second reset. Ocasionally when I hit a bump I will get the traction control disabled message but the truck no longer goes into reduced power mode. That is when the truck actually runs. Oh and the keyless entry dosnt work when the truck won't start. When the truck starts and runs normally the keyless entry works.
 
#7 ·
Bigrick31 said:
Everything works as it should in the vehicle the only time then door locks or headlights give me trouble is randomly when I hit a bump in the road which will cause the truck to either shut off completely or go through a 5 second reset. Ocasionally when I hit a bump I will get the traction control disabled message but the truck no longer goes into reduced power mode. That is when the truck actually runs. Oh and the keyless entry dosnt work when the truck won't start. When the truck starts and runs normally the keyless entry works.
I would be checking ground connections as it sounds like one is loose
It may be tied into the traction control message not sure but most likely its because of low voltage(loose connections can cause this)

First clean both battery cables and terminals to see its a bad connection at the battery(do this first)
 
#8 ·
Ok I cleaned the battery terminals really well and I still get nothing. I checked continuity between the battery negative and the ground wires that go to my frame and engine block both test good. I did notice when I tried to start the truck after cleaning the battery terminals that I cold hear what sounds like the fuel pump making a pfft sound after every failed start. Just to clarify the truck will not crank but all electronics work just fine. Again after attempting to start the truck I had to disconnect the battery because there was a bulb in each headlight that remained on.

Edit- Dont know if this matters but my fuel gauge reads empty however when the truck last ran I had close to a full tank of gas.
 
#9 ·
Bigrick31 said:
Ok I cleaned the battery terminals really well and I still get nothing. I checked continuity between the battery negative and the ground wires that go to my frame and engine block both test good. I did notice when I tried to start the truck after cleaning the battery terminals that I cold hear what sounds like the fuel pump making a pfft sound after every failed start. Just to clarify the truck will not crank but all electronics work just fine. Again after attempting to start the truck I had to disconnect the battery because there was a bulb in each headlight that remained on.

Edit- Dont know if this matters but my fuel gauge reads empty however when the truck last ran I had close to a full tank of gas.
Sounds like a module
 
#11 ·
Bigrick31 said:
I can find used BCMs on ebay for about $30 then I guess I just need to tow the truck to the dealer to have it programmed or can i just bring the module to the dealer and then install after programming or is a used BCM a bad idea?
I don't know I haven't had to it so far but I recommend the programming be left to the dealer(I went through this kind of issue with my PCM except it kept my truck from starting)
 
#14 ·
Got the new BCM in just now called the Cadillac dealer near me and they said I had to have the new BCM installed in the vehicle for them to reprogram it. Im going to install the new BCM and have my truck towed over to the dealer. If this dosnt work they are going to run a diagnostic for me to see whats wrong.
 
#16 · (Edited)
Bigrick31 said:
So its $150 for the dealer to reprogram the BCM it would have been $300 but I Already installed the BCM prior to having the vehicle towed to the dealer. They will call me tomorrow to let me know if that worked. If not its $450 for an extensive diagnostic.
Its around the same ball park on price I paid to have the pcm replaced in my truck
 
#19 ·
Just got the truck back from the dealer. They said after they reprogrammed the BCM the truck would crank but wouldnt start. They ended up finding a bad ground wire behind the engine. They said it looked good visually but the wires under the insulation broke apart. With reprogramming the BCM and finding and fixing the bad ground it only cost me $445 which is a huge relief.
 
#20 ·
Bigrick31 said:
Just got the truck back from the dealer. They said after they reprogrammed the BCM the truck would crank but wouldnt start. They ended up finding a bad ground wire behind the engine. They said it looked good visually but the wires under the insulation broke apart. With reprogramming the BCM and finding and fixing the bad ground it only cost me $445 which is a huge relief.
Glad to hear you got it fixed(just wish you didn't have to spend the money on the bcm before you found the bad ground cable)
 
#23 ·
Turns out my troubles are not over yet. The truck drove fine for about a week after the dealer fixed it. There were some minor issues like a rough idle or my projected fuel economy being a lot lower than usual but I figured the truck just had to re learn a few things since a lot had been changed. However I was going to go for a bit of a drive this past weekend and right when I pulled out of my driveway I get hit with the "service stability system" message and reduced engine power message. I got a tow truck on its way right now to pick the truck up and take it to the dealer. The only issue is if I try to drive the truck right now it drives fine hopefully the dealer can replicate the problem.
 
#24 ·
Bigrick31 said:
Turns out my troubles are not over yet. The truck drove fine for about a week after the dealer fixed it. There were some minor issues like a rough idle or my projected fuel economy being a lot lower than usual but I figured the truck just had to re learn a few things since a lot had been changed. However I was going to go for a bit of a drive this past weekend and right when I pulled out of my driveway I get hit with the "service stability system" message and reduced engine power message. I got a tow truck on its way right now to pick the truck up and take it to the dealer. The only issue is if I try to drive the truck right now it drives fine hopefully the dealer can replicate the problem.
Given the messages it may be the PCM as the stability system is tied into the PCM

I know how you feel about it I was in your shoes but my truck wouldn't even start or crank(the data bus for the throttle went down and the PCM shut the engine down) and I was lucky it did or i would have plowed through a Walmart as when I got it home via tow truck and got a code scanner I found out the tps was showing I had the pedal to the floor(not good)

You did the right call by not taking the risk and driving it when it showed the message

Mine would lag on the throttle before the PCM died
 
#25 ·
Your story with the TPS sounds scary it makes me wish we had the old cable style system.

as for the PCM I just replaced it a couple of weeks ago with a tested good working unit. I did this when I first started getting the service stability message I first changed out the Accelerator position sensor then the entire throttle body then the PCM and finally I replaced the BCM. If it is the PCM then my original PCM and the PCM I purchased online would have to have the same problem which seems unlikely or am I missing something here? Also I only get the message when I hit a bump or in this case when I drive the truck in and out of my driveway I actually drive off of the curb as my driveway is wider than the slanted part that merges into the street.

What happened this weekends was I backed out of the driveway firs the rear tires drop off of the curb and then the front ones. Then when I am far enough back I put the truck into drive and thats when I got the error messages. However I just did this exact same thing right now to drive the truck up onto a tow truck and the truck worked just fine.
 
#26 ·
Bigrick31 said:
Your story with the TPS sounds scary it makes me wish we had the old cable style system.

as for the PCM I just replaced it a couple of weeks ago with a tested good working unit. I did this when I first started getting the service stability message I first changed out the Accelerator position sensor then the entire throttle body then the PCM and finally I replaced the BCM. If it is the PCM then my original PCM and the PCM I purchased online would have to have the same problem which seems unlikely or am I missing something here? Also I only get the message when I hit a bump or in this case when I drive the truck in and out of my driveway I actually drive off of the curb as my driveway is wider than the slanted part that merges into the street.

What happened this weekends was I backed out of the driveway firs the rear tires drop off of the curb and then the front ones. Then when I am far enough back I put the truck into drive and thats when I got the error messages. However I just did this exact same thing right now to drive the truck up onto a tow truck and the truck worked just fine.
No worries on that as the PCM shut the engine off right after it went into reduced power mode(I am thankful it did as I wasn't the only one in the truck) plus it would be a bad image on us caddie owners had it barreled into Walmart that day(remember the runaway Toyotas) I doubt I would have survived that day but never know and I don't think I would have wanted to find out

If I did have that happen and I survived my truck would have been totaled most likely due to the impact with the building

I am wondering if a wheel sensor is bad or a wire is loose/chaffed though given how the message is at random

I have only seen that message one time and that was when I had overworked my brakes(was on a trip so I didn't get to check for codes and the issue went away after I restarted the truck)
 
#27 ·
I actually don't know if my wheel sensors are still working. I purchased a set of 18s from someone who had just purchase a 2010 escalade and wanted aftermarket wheels. I never got around to getting the the new wheels set up to my wheel sensors. The dealership just called and asked me if I had already replaced my AP sensor or if I had replaced the ignition switch. I told them I changed the APS but not the ignition so that's where they think the problem is coming from at the moment.
 
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