So the expy doesnt get driven much anymore other than towing boat/camper. About a year ago i noticed the headlights on while it was sitting in the driveway, switch was on auto, but it was daytime, car was off/locked. Opened the door and turned it to off and lights shut off. I didnt think much of it other than it was a "glitch" and made a habit not to leave the switch on auto.
fast forward a few months. about the same time i installed an aftermarket radio, towing the boat, the "parking brake engaged" light came on. i checked the brake switch, even unplugged it, no change. Then randomly while driving the warning shut off.
I assumed it was something to do with towing, or hot weather. it came and went for a while and i was not able to isolate the cause.
only post online i could find about it was that the cluster was bad.
after some logical thought, i put my bet on the SJB. Since the SJB takes the analog brake signal and converts it to CAN for the cluster to read, it made more sense that the SJB was bad or causing the issue.
I pulled the cluster just to check and make sure there was nothing out of place, all looked good so i tore into the SJB.
I could have just bought a new SJB for about 200 bucks, but then it has to be programmed, etc.
It ended up being a bad resistor. It was on the input voltage divider. They use a bunch of 4x resistor arrays for various inputs. I found two more bad resistors within the same array that i am pretty certain were on the headlight input circuit. I wasnt able to verify exact pinout, but it was tied to the same connector.
The parking brake circuit i traced 100%, the circuit uses two voltage dividers going to two separate shift registers to convert the analog signal to digital. i think it uses two for redundancy, which is why the warning light worked correctly when the brake was actually engaged, pulling the circuit to ground. but when it was off, one of the voltage dividers was floating due to the open resistor and that is why i was getting the warning.
The symptoms i was having seemed very "loose connection" like.
here are pictures of what i replaced. if you arent good with a soldering iron, just replace the SJB. it was a pain to take apart, some huge ground pads soaked a lot of heat making desoldering difficult on a few header pins. part is a 120k resistor array, 1206 package size.
fast forward a few months. about the same time i installed an aftermarket radio, towing the boat, the "parking brake engaged" light came on. i checked the brake switch, even unplugged it, no change. Then randomly while driving the warning shut off.
I assumed it was something to do with towing, or hot weather. it came and went for a while and i was not able to isolate the cause.
only post online i could find about it was that the cluster was bad.
after some logical thought, i put my bet on the SJB. Since the SJB takes the analog brake signal and converts it to CAN for the cluster to read, it made more sense that the SJB was bad or causing the issue.
I pulled the cluster just to check and make sure there was nothing out of place, all looked good so i tore into the SJB.
I could have just bought a new SJB for about 200 bucks, but then it has to be programmed, etc.
It ended up being a bad resistor. It was on the input voltage divider. They use a bunch of 4x resistor arrays for various inputs. I found two more bad resistors within the same array that i am pretty certain were on the headlight input circuit. I wasnt able to verify exact pinout, but it was tied to the same connector.
The parking brake circuit i traced 100%, the circuit uses two voltage dividers going to two separate shift registers to convert the analog signal to digital. i think it uses two for redundancy, which is why the warning light worked correctly when the brake was actually engaged, pulling the circuit to ground. but when it was off, one of the voltage dividers was floating due to the open resistor and that is why i was getting the warning.
The symptoms i was having seemed very "loose connection" like.
here are pictures of what i replaced. if you arent good with a soldering iron, just replace the SJB. it was a pain to take apart, some huge ground pads soaked a lot of heat making desoldering difficult on a few header pins. part is a 120k resistor array, 1206 package size.
