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CTS 2004 3.2L
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28 Posts
Discussion Starter #1
so i have a Cadillac CTS 2004 3.2L with Automatic Transmission
for the past year i have had the same symptoms as everyone here. fuel and temp gauges suddenly shut off, traction and security lamp illuminating and Service Theft system message, AC disengaging the compressor clutch then engaging again (like when press the AC off button)
however i had one more problem no one seems to have it or pay attention to it, battery draining, whenever i leave it a full day or two the battery will drain badly. i tried to :
Reprogram the current ECU
new battery
checked all voltages from battery, alternator and fuse box. all good and no electrical discharge
however if i disconnect the ECU harness while the battery is still connected no draining even after a full week.
so this made me more sure that ECU was faulty as everyone suggests
got a used ECU and VTD module then programmed them. they gave me a good 4 hours of false hope :cry: then all the stupid symptoms back again
and more frequent too ,fuel and temp gauges suddenly shut off, traction and security lamp illuminating and Service Theft system message add to that now SIR
sometime the radio will completely shut off then turn on again

i have a tech ii available
diagnosing is no help it says lost communication with either ECM OR rarely BCM. and sometimes there are no codes even
i got the online Subscription for SPS to make sure all are programmed to the recent most updated calibrations

should i try another ECU or should i get A new BCM
has anyone actually solved this issue completely
anyone has any suggestion to solve this issue
 

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CTS 2004 3.2L
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28 Posts
Discussion Starter #2
sadly not even one reply even though almost 100 views,
anyways i decided to get a new BCM i will update you guys if it works with me. in case anyone faces the same problem as me i know how irritating and confusing it is
i should get it in two weeks

just an FYI the problem didn't appear with me for almost a week now after last time it happened
almost 1000 km i drove it, but somethings stopped working like the driver seat adjustment and the wipers could be irrelevant

but as i read online all the symptoms i had happen when the BCM fails so yeah this is why am getting a new one..
 

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4 Posts
I had the same issue with my 04 CTS. Was told it was the ECM so I replaced it. Cant tell you if it worked yet because I'm having trouble with the paskey III relearn 😭
 

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2007 CTS 2.7L
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510 Posts
All your symptoms point to a dying battery. it COULD be the ECM, but I would really get the battery and alternator checked first and maybe replace the battery anyway.

Why? Because the dying battery will drain on it's own when sitting. when you start the car, the alternator engages and charges the battery and electrical system. During that time the whole electrical system is low voltage and that causes a lot of weird things on these cars. Even though these will start and run, I have seen personally and here on the forums weird behavior but NOTHING tells you it is low voltage related.
 

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2007 CTS 2.7L
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510 Posts
I want to add that when I say "low Voltage", that is relative to the ECM and system needs. It expects 12.x to 14.x depending on running, charge levels, alternator, etc. and is getting less that needed or expected. Typically not enough for many other cars to cry about, but ours do.
 

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2005 CTS 3.6 - 165k miles
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49 Posts
All your symptoms point to a dying battery. it COULD be the ECM, but I would really get the battery and alternator checked first and maybe replace the battery anyway.

Why? Because the dying battery will drain on it's own when sitting. when you start the car, the alternator engages and charges the battery and electrical system. During that time the whole electrical system is low voltage and that causes a lot of weird things on these cars. Even though these will start and run, I have seen personally and here on the forums weird behavior but NOTHING tells you it is low voltage related.
Is it true that we are unable to swap in a new battery ourselves(something to do with theft system)? I've got the money for a new battery but i can't afford hundreds of dollars from a dealership. Any advice? My car started going into "battery saver mode" today, killed the ac. Went by autozone and battery was at 29% charge. My buddy thinks its the battery because alternator seems to be functioning fine, though alternator was not able to fully compensate for the weak battery at idle (system was around 10.5-11.2 volts with ac off). if turning the ac on, the system would dip even lower than 9 volts. on my way home while highway driving, car was between 13.6 and 14.8 volts until i pulled into the driveway, and it promptly dipped to ~11 volts. Should i replace the battery and alternator, or just the alternator, and can i do it myself?
 

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CTS 2004 3.2L
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28 Posts
Discussion Starter #9
thank you
greenmachineiijh
for the reply, but i actually did replace the battery didn't solve the problem. as for the alternator it charges well and i also checked the diode pack and it is still ok no discharge. before i changed the ECU battery was draining badly but with the new ECU battery is always around 12.3 volts overnight
 

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CTS 2004 3.2L
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28 Posts
Discussion Starter #10 (Edited)
i got the New BCM a week ago and i was so anxious to mount it and see the results
here's the how to replace
first of all there are two Body control modules "BCM" in this car
"DIM" Dash Integrated Module and "RIM" Rear Integrated Module
here's the location of both
#2 in the top is DIM
#4 in the bottom is RIM
573336

DIM and RIM location "LINK for the picture in case it didn't show"

the one i got was the DIM which is in the front passenger side kick panel
there are two bolts holding the panel in the back and one screw in the top right of it
and when you drop it down you will see the BCM as it's the mounting for it
should not take from you more than 5min
573337

DIM removal "LINK for the picture in case it didn't show"

after that i programmed the VIN in it using the TECH II and all done NO ONLINE SUBSCRIPTION NEEDED
it's done with the tech ii only

now as i said it's been a week and everything is working as it should the problem hasn't appeared since
I hope this helps anyone who is frustrated by this issue like me and who tried replacing the ECU but didn't solve the problem for him
 
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