Transmission Filter change, odd problem

[SteelCityFan]

I changed my transmission filter for the first time yesterday, and everything went great. The truck now shifts great and I have had no problems with about 60 miles so far. This morning on the way to work though, I was going down the road and my traction control light turned on and so did my parking brake light. I knew there was no way my parking brake light would be as I was going 50 and wasn't being slowed at all. I figured it was just a weird intermittent thing because my traction control does come on like that about once a month. The light continued to stay on all day today, and I was wondering if I should be worried about anything or what exactly would be causing this to happen, was it just coincidence that this happened after I changed the filter. I did have the truck on jack stands for about 3 hours or so with the parking brake on, but I have done this before with no problems. Thanks for any of the help if you guys have it!

 

[Pittdawg]

I changed my transmission filter for the first time yesterday, and everything went great. The truck now shifts great and I have had no problems with about 60 miles so far. This morning on the way to work though, I was going down the road and my traction control light turned on and so did my parking brake light. I knew there was no way my parking brake light would be as I was going 50 and wasn't being slowed at all. I figured it was just a weird intermittent thing because my traction control does come on like that about once a month. The light continued to stay on all day today, and I was wondering if I should be worried about anything or what exactly would be causing this to happen, was it just coincidence that this happened after I changed the filter. I did have the truck on jack stands for about 3 hours or so with the parking brake on, but I have done this before with no problems. Thanks for any of the help if you guys have it!

Mine does this intermittently after parking on an incline. I think it's a known quirk with the electronics on the GMT 360s.

 

[SteelCityFan]

Does this problem just to away eventually, just bothers me I don't like lights on my dash

 

[The_Roadie]

Mine does this intermittently after parking on an incline. I think it's a known quirk with the electronics on the GMT 360s.

Awww, man. Saying that is like waving a red flag in my face.

The truth is, I never traced a parking brake lamp problem for anybody before. So into the shop manual I go, starting at the Parking Brake section. No schematic there. Stupid. In the Instrument Panel section I can see that the Parking Brake warning lamp is lit up by a data comm message, not by being wired to the console switch near the lever. So that leads me to believe the data comm message is coming from the BCM, and in the Wiring Harness section I find there is indeed a wire at the BCM connector for the parking lamp switch, circuit 1134. Since the Helm GM shop manual indexing is one of the worst I've ever had the misfortune of interacting with in decades of tech writing, I found a clue in the Hydraulic Brake section, which *did* have a schematic showing the park brake lever switch going into the BCM. But it ALSO had the schematic for the Brake Fluid Level Switch, which sends a signal to the EBCM (ABS controller) and the Park Brake lever signal *AND* the low fluid level signal EACH can send a message to the instrument cluster to light up the same warning light.

So the warning light is probably from the EBCM, not the parking brake lever, and is either caused by a bad ground connection G107 for the fluid level switch, or a problem with the EBCM that also runs the traction control. Its ground often gets corroded, and is down in the vicinity of where you were working.

The parking on the incline issue I bet is related to the brake fluid reservoir switch.

 

[SteelCityFan]

Very informative as always. Maybe if I find free time in my college life (haha that's a joke no engineering student has free time) I can try to find some grounds and see if they are bad or not, but it's honestly probably not worth my time. Thanks for the info though guys, its always appreciated .