I have a 2004 trailblazer with 23,000 original miles.
Ive been getting a PO455 code for awhile now and the other day when I started it the ABS, BRAKE, SERVICE 4WD lights all stayed on and a warning chime chimed for a minute or so. I also noticed the heater won’t work and when you turn the engine off and open the door the radio doesn’t turn off and the door lock delay chime and delay locking also won’t work. But the doors do lock, just with no delay.
The PO455 code isn’t related to the other warning lights I’m sure. But I have installed a new AC gas cap, AC ignition switch and two AC evap solenoid valves.
One on the engine and one back by the gas tank. This is my wife’s car and she won’t drive it anymore until it’s fixed. So I would really appreciate any help to figure this out.
PS, the ign sw, gas cap and evap valves were changed several years ago. Thanks, Karl

Thanks for your suggestions. I’m pretty sure all the problems are related to one cause. I’ve gone over every ground on this car. I even removed any paint found at ground points.
I have found that all these issues happen at the same time. The 4WD won’t transfer from RWD also. This car has a switch that you turn to select 4WD.
On the rare occasion that the lights don’t stay on, all the problems I described work perfect. All of them!
Then the next time the lights stay on and they all act up again.
I’ve decided to replace the ignition switch again. They seem to be one of the most common fix’s. Then I’ll try the BCM. If none of that works then I’ll do what my wife suggested! Trade it in on a new car...