You are here:

Cadillac Repair/1999 Cad Deville Concours drastic power drain.


QUESTION: Car Stats: 1999 DeVille Concours 4.6 Liter

Car History: Previously father's car, he stated but is not sure when these issues came about (time frame).1.A/C does NOT blow cold air but does blow tepid air.
2.Radio does NOT work. No lights. No Sound. (Speakers do "thump" when disconnecting/re-connecting battery terminal)
3.Power drain, battery goes flat within a couple of minutes.

Work that I have completed:1.Recharged battery.
2.Measured Ampere draw from battery around top peak at 4.8mA
3.Connected battery terminals and pulled one fuse at a time and checked draw at each fuse locations on terminal block in engine compartment
(NO issues found at terminal block in engine compartment)

4.Disconnected Negative terminal at battery and measured mA draw between Negative and Positive terminals
a) Pulled Radio/Phone Fuse from terminal block in trunk, found draw to be at around 0.02mA
b) Disconnected Radio harness from back of radio, thinking radio was defective and was draining battery
c) Re-installed Radio/Phone Fuse (this fuse also allows electric windows and door locks to operate)
d) Battery held charge longer....couple hours.
e) Disconnected Radio Power Ampilfier. (No longer hear speaker "thumping")
f) Also removed - reinstalled Comfort Fuse during ampere draw testing.

5.Battery Drain issue seemed to have disappeared, drove from San Jose CA to Las Vegas NV (about 600miles) and had stopped a couple of times turning ignition off and on during travel. Upon parking car for the night and turning ignition off, heard clicking noise from behind dash, passenger side. Noise stopped after a couple of minutes. Parked cadillac overnight.

Next morning opened driver side door by unlocking door with key. Inserted key into ingition and tried to start engine. When ignition got to "start" position horn beeped. Turned key off, tried again with same results. (Think it maybe secuirity alarm). Also the lights on instrument panel and digital readouts were delayed in turning on. Climate control readouts stay on for a short period of time then disappear and are replaced with double dash where temperature readings would be. At this point found that the clicking noise heard from previous night during shutdown was the fan blower behind glovebox.

a) Removed Comfort Fuse - Eliminated Horn Alarm during startup
b) Removed Amplifier Fuse - just in case
c) Removed Radio/Phone Fuse - just in case

OLD & NEW ISSUES:1. Issue of none operation of radio
2. Issue of no A/C
3. Alarm (Horn) sound when starting engine
4. No automatic door locks and window operation (due to removed fuse)
5. Delay of instrument dash data
6. No climate controls

Battery is HOLDING charge at this point and starts with no issues other than what is listed above

My question to you all is; (Thank You All in advance for any solutions)
1) Has anyone experienced any of these same issues?
2) Any known solutions to the above issues?
3) Could these issues be due to a defective module?

AC-Heater Programmer Module
(BCM) Body Control Module
(ESC) Electronic Stability Control Module
Radio Amplifier

ANSWER: Hi Scotr,

Are you working with a factory service manual? Make sure you are dealing with all fuse boxes in this vehicle as per owners manual.
You have done your homework on this.
I am not a parts changer however I would be leaning heavy at a defective BCM. As I was reading, this is what popped into my mind before you mentioned. After all it is the body control modules which links everything into sync.

[an error occurred while processing this directive]---------- FOLLOW-UP ----------

QUESTION: If I get a BCM from a junk yard would I have to have this "flashed" by GM or could this just be connected. I would expect to use a replacement from a cadillac that had body damage. Don't think a body damaged vehicle would be in for electrical issues, just scrapped by insurance after an accident.


Very rarely do I have the opportunity to have a questioner so knowledgable that did such extensive testing before presenting their question. Very refreshing.
I did ask if you had the 1999 service factory service manual for a reason. The manual will take guesswork out of the equation.
Reviewing your question did cause me deep concern about the parasitic draw to discharge the battery that quickly because a draw like that could mean a short to ground potentially causing a fire and now the problem no longer exists. This again could go back to the BCM which is basically the brain of the vehicle. With all the complaints you listed that is the reason I suspected the BCM as I was reading before getting to your possibility of a BCM.

I am sure you looked on the Internet for a rebuilt or new. BCM. I did and see them very pricey. I found a used one on EBay for $119 and further looking revealed no guaranty!
Your thoughts of getting one from a crashed one are very good, but I will issue another caveat. Try to get from a sealed car if possible where the doors are on and windows closed. The reason being is moisture can be an issue for you and this electronic item that should be mounted in the rear seat area.
We repaired many floods where water never reached the computer or the other modules only to have them fail later from residual moisture. Just something for you to consider. I realize this may make your search more difficult, but you don't want to pay a lot of money for a part that will be doomed to fail in the near future.
I scrolled through the interchange and it looks from a quick glance should be 1994-1999, but please confirm.
As for having to flash it, I will be perfectly honest, I simply do not remember.
Yes, I believe it will have to be reprogrammed to your VIN.
Don't go rushing to the dealer as so many do.
I would recommend finding a local respectable repair facility that has a tech II scanner and have them do it for less than half what a dealer charges. I try to steer everyone away from the dealers because of expense. You will also get the answer they can't program a used computer and you will need to buy a new one from them.
I worked in  GM dealers for 11 years. They make money selling over priced new parts and never will install used. If the vehicle has a transmission shifting issue and there is any type of aftermarket equipment on the vehicle, even a stereo, to them the stereo would be causing the shifting problem. They will replace as many parts as your wallet can afford and the problem never got fixed.

It is also my understanding there are places on the Internet that can flash the computer without the vehicle, but I am not sure how they can do that.

Good luck and let me know how it works out.


---------- FOLLOW-UP ----------

QUESTION: Sorry forgot about your question.... No I do not have a service factory service manual, just a Haynes and lots of experience from past cars I have owned. Reading the schematic in the Haynes helps some.

Your welcome I try to help someone with my problem as much as I can. I understand very well when an idividual with some knowledge goes in and monkies around and you have to debug and put everything back to factory then find the original problem. Especially feel for you by having to diagnose via text, sight unseen.

I only bring my cars back to the dealer if it is under warrenty. The dealer per hour is amazing. I am hoping it would be something easy like a stuck relay or loose wire... not looking forward to replace any "box" with lots of circuitry. May be a silly question but whats in the box that requires flashing to the VIN?

What bugs me alot is that by having pulled the AMP and disconnected the radio harness in San Jose then driving to Las Vegas (having stopped and restarted the engine a few times for gas and restroom breaks) The next morning everything was fine. I had pulled and replaced every fuse in the trunk one at a time. Now with the "COMFORT" fuse in and trying the ignition again (turning it to the start position) the horn goes off... like an alarm. Forced to pull the comfort fuse so the windows/door locks do not work. I do hear the fan blower behind the glove box working. Is there something that happened that made the alarm (i guess the anti theft alarm) to go off, would have figured that it would have gone off when I disconnected the radio in San Jose...

The Vin denotes certain options that are enabled through the circuitry I guess. To be honest with you that is far above my pay grade. Lol
The factory service manual will assist you greatly with diagnostic flow charts. The best tool out there that will save you tons of money. You should be able to find one on EBay or Craig's for about $100. Haynes and others are not detailed enough and the factory service manual was my bible for repair.
I haven't been on this site for a while and they may now go back far enough for you If they go back to 1999 you can download the manual for about $30.00.
Give it a shot.

Good luck!


Cadillac Repair

All Answers

Answers by Expert:

Ask Experts


Rob Painter


Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?


Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.

©2017 All rights reserved.

[an error occurred while processing this directive]