Bleeding ABS with Tech 2

[Brett Baker]

I have a 95 c3500 with RWAL that blew a rear brake line and emptied the reservoir, allowing the abs unit to get airbound. It is OBD1. I have a tech 2 and I have used it to do fuel system related things so it does communicate with the truck. I get around good in the scanner on my later model trucks but I seem to be lost on this truck. Trying to find the bleed or test function and I’m getting nowhere. I load the year, LD truck, chassis then the next screen takes me to select product line C G K etc. I choose C then RWAL. Next screen I choose special functions, then function test. It tells me a few warnings, then ignition off, 5 second countdown, ignition on then the screen just stays on turn ignition on. I’ve started over a half dozen times, and no different. If I check for abs DTCs it says waiting for data, and just stays stuck there, no data but no error either. Fuses are good, Brake warning light on dash is on. I don’t see an ABS light on but I’m not sure if this year has one? Brake warning light may be it? Any help would be appreciated

 

[deadbeat]

Not sure on how to use the scanner, but if you can get up to about 25 - 30 mph in gravel and slam the brakes and let it slide, it will purge the air out of that abs unit. It took me a ton of time to get it out of mine after replacing my rear lines.

 

[delta_p]

I have a tech 2 clone but I have a '96 and it only has the 3 sensor 4wal. On this there is no countdown or cycling of the ignition, as long as it is on with engine off, after the warnings it establishes communication and then says depress the pedal and it cycles the ABS about 4 times.
I went through the rundown for a 1995 and i see what you are talking about. are you starting with ignition in the on position first? are you turning to the on position or starting the truck? Does it start the test at the ignition on screen if you just depress the brake pedal?

BTW this is a good resource for Tech2 paths. It's all paths though even more than available for your truck but you could probably reduce this down if needed.
https://gsi.ext.gm.com/userguides/GM_Tech2_Paths.pdf

 

[delta_p]

Also, if i can get to that screen just scrolling through function sitting at my desk then that means no communication is occurring to this point. So i would go and use the function to pull the VIN or something just to make sure you do have communication from the unit and through the DLC connector to the truck.

 

[Brett Baker]

I have a tech 2 clone but I have a '96 and it only has the 3 sensor 4wal. On this there is no countdown or cycling of the ignition, as long as it is on with engine off, after the warnings it establishes communication and then says depress the pedal and it cycles the ABS about 4 times.
I went through the rundown for a 1995 and i see what you are talking about. are you starting with ignition in the on position first? are you turning to the on position or starting the truck? Does it start the test at the ignition on

Wow, thanks for all the work Delta!
I have communications because I can watch live data like fueling (diesel) and transmission function. I can even turn on various lights.
I have tried it starting with it running, then off, then key on, not running key on, then off, etc, basically every combo available.