My 99 deville 46k has started to have a strange issue when you step on the brakes the dash info display goes crazy and the hvac blower goes to high radio goes blank and the traction control light stays on(until u restart car) read other posts changed alt. volts were 13.6 prior and 14.2 after new unit. clean batt connections and ground points for batt cables but problem still continues. funny voltage at battery is 14.2 but on dash info display says approx 13.6 volts ???. I have read previous posts here and am ready to loose it. Love this low mileage caddy but whats up Is there a ground or cable that goes bad on these models

 

Unfortuneately there is not any one cause. There should be codes stored, you need to post them.

 

I will get the many stored codes and post thanks

 

I cleared all codes than recreated the problem and it goes like this:
Step on the brake and hold, shift selector flashes, theft system flashes,
car may not restart flashes, servive air bag flashes than high blower comes on than radio goes off and blank than traction control light comes on let go of brake and only TC light stays on. now for the CODES:
PCM P1602,P1604,P1605, P1610, P1626(current)
IPC B2750,U1016,U1152,U1064,U1033,U1088,U1040
ACM U1016, U1064, U1096
IRC U1064, U1096
SDM U1301
ICS U1301,C1298, U1016
PZM U1301, U1064,
RFA U1300
All other codes say history
I also checked volts at battery with high end digital fluke about 13.8v
and dash says 13.2-13.3v new Batt and 2nd alt(reman) I am getting to be an expert at changing alt in less than 1 hr now

This problem happens with car running or not just with ignition on.
Any thoughts would be great
Thanks Ed