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99 Deville Parking Brake and AC issue


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Hi all,

This is my first post (been able to fix all my other problems by searching old topics) so please bear with me. First, After having not driven the car for about 3 weeks, the car took several attempts to start and then once on the parking break would not release when I shifted out of park. I manually released the break and tried again with the same results. Second, my AC now only blows from the defrost and lower vents. This same problem occurred with a Jeep I once owned and it was a vacuum hose but since the caddy is a little more complicated, I thought it might be something electronic. I checked my codes and didn't find anything related to the brake or AC. Recently a buddy replaced the crank sensors and a dying battery but none of these problems occurred for several weeks after that work. I checked my codes and got the following:

pcm P0603 History

ipc B1552 History

pzm B1558 History

irc B1770 History

irc B1771 History

Any Help would be appreciated

Thank you,

Ben

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The parking brake release is on the same vacuum circuit as the HVAC system and defrost is the default mode (loose vacuum and it defaults to defrost). You have a vacuum leak. Most probable leak point is the parking brake release diaphragm. Check that first. If that is OK, then pull the vacuum supply hose to the cabin where it enter the cabin at the passengers side firewall. If you have vacuum there, then the leak is in the cabin under the dash somewhere. If not, then trace the line back and find the leak under the hood.

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This is where you can get a description of your codes, describe them here for us next time

http://myweb.accessus.net/~090/dtcobd2.html

P0603 - Control Module Long Term Memory Reset

B1558 - BCM EPROM Checksum Error

B1552 - Keep Alive Memory (KAM) Error

B1770 - Cassette not responding

B1771 - Cassette tape slow

The Cadillac HVAC works via vacuum, mechanical and servo stepper motors. It does not appear that you are setting a code for a stepper motor, so i would think that the problem is mechanical or vacuum.

Since you are having problems with the parking brake that is controlled by the ACM, which also controls the hvac, I would check all vacuum lines, including the vacuum tank for leaks all the way back to the ACM.

Also check the parking brake vacuum servo for a bad diaphram, which also can drop system vacuum

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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The parking brake release is on the same vacuum circuit as the HVAC system and defrost is the default mode (loose vacuum and it defaults to defrost). You have a vacuum leak. Most probable leak point is the parking brake release diaphragm. Check that first. If that is OK, then pull the vacuum supply hose to the cabin where it enter the cabin at the passengers side firewall. If you have vacuum there, then the leak is in the cabin under the dash somewhere. If not, then trace the line back and find the leak under the hood.

Thanks much for the help. I'm not sure how to check a vacuum line, can you break down the procedure for me or do I just need to go to a mechanic.

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This is where you can get a description of your codes, describe them here for us next time

http://myweb.accessus.net/~090/dtcobd2.html

P0603 - Control Module Long Term Memory Reset

B1558 - BCM EPROM Checksum Error

B1552 - Keep Alive Memory (KAM) Error

B1770 - Cassette not responding

B1771 - Cassette tape slow

The Cadillac HVAC works via vacuum, mechanical and servo stepper motors. It does not appear that you are setting a code for a stepper motor, so i would think that the problem is mechanical or vacuum.

Since you are having problems with the parking brake that is controlled by the ACM, which also controls the hvac, I would check all vacuum lines, including the vacuum tank for leaks all the way back to the ACM.

Also check the parking brake vacuum servo for a bad diaphram, which also can drop system vacuum

Thanks for the info. This may be a little out of my league but at least I now have a jumping off point.

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The parking brake release is on the same vacuum circuit as the HVAC system and defrost is the default mode (loose vacuum and it defaults to defrost). You have a vacuum leak. Most probable leak point is the parking brake release diaphragm. Check that first. If that is OK, then pull the vacuum supply hose to the cabin where it enter the cabin at the passengers side firewall. If you have vacuum there, then the leak is in the cabin under the dash somewhere. If not, then trace the line back and find the leak under the hood.

Thanks much for the help. I'm not sure how to check a vacuum line, can you break down the procedure for me or do I just need to go to a mechanic.

Have an assistant put the car in gear and hold the brake while you lean in and unplug the vacuum line on the parking brake release mechanism. Is there vacuum (suction) at the end of that hose? If so, the parking brake release diaphragm is leaking. If not, then move to the firewall and check the same way, except you only need to be idling. No need to be in gear at this point.

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  • 2 weeks later...

The parking brake release is on the same vacuum circuit as the HVAC system and defrost is the default mode (loose vacuum and it defaults to defrost). You have a vacuum leak. Most probable leak point is the parking brake release diaphragm. Check that first. If that is OK, then pull the vacuum supply hose to the cabin where it enter the cabin at the passengers side firewall. If you have vacuum there, then the leak is in the cabin under the dash somewhere. If not, then trace the line back and find the leak under the hood.

Thanks much for the help. I'm not sure how to check a vacuum line, can you break down the procedure for me or do I just need to go to a mechanic.

Have an assistant put the car in gear and hold the brake while you lean in and unplug the vacuum line on the parking brake release mechanism. Is there vacuum (suction) at the end of that hose? If so, the parking brake release diaphragm is leaking. If not, then move to the firewall and check the same way, except you only need to be idling. No need to be in gear at this point.

Hi there,

thanks to all Caddy lovers who gives all the support and effort. for me I have the same prob. but with 2000 DTS can you please show me on pic where is the vacuum generator under the hood so I can track for any leak and where is the release diaphragm lookated and for the A/C do I have to see the conectors for vcuum or it will automaticly work

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Hi there,

thanks to all Caddy lovers who gives all the support and effort. for me I have the same prob. but with 2000 DTS can you please show me on pic where is the vacuum generator under the hood so I can track for any leak and where is the release diaphragm lookated and for the A/C do I have to see the conectors for vcuum or it will automaticly work

Your year model Cadillac does not have a vacuum or electric park brake release mechanism.

All you have to do is press the park brake pedal to release.

If you are having problems with HVAC (A/C) controls, you should start a new thread for that topic.

For what its worth, the only vacuum assist on your model Cadillac is power brakes. All the HVAC doors are electric.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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