92-2002 Kelsey Hayes 4 Wheel ABS "Power Bleed"

[hatzie]

This will fix the GMT400 spongy brake pedal problem after the ABS ingests air from a broken brake line or the ABS gets angry with you but isn't dead. You should do this when you change the brake fluid every 24 months or so.

I do a pressure pot bleed til all four wheels run clean, power bleed the ABS motor, and pressure bleed the system again at all four wheels to rinse the crud out that the power bleed just broke loose.

First off... This is ONLY for the later 4wheel ABS systems.
My recommendation on the early GMT400 88-92 RWAL trucks is to remove the ABS motors, hook the rear brake line directly to the combination valve, and do a 4 wheel bleed. This is the ABS with the long narrow box mounted to the side of the Combination valve under and toward the LH fender from the Master Cylinder. Some 92 had RWAL and some had the Kelsey Hayes 4WAL.
https://www.gmt400.com/threads/1990-c1500-abs-rwal-removal.11427/

I have done this on two GMT400 trucks... 1995 K1500 & 2000 GMC C2500 Sierra. I've also done this on a couple off topic GM vehicles as well... 2005 Silverado 2500HD & 2009 Impala SS.
It fixes the spongy brake pedal.

Tools...
Motive type pressure bleeder and master cylinder adapter. Mine is a weed sprayer and home brew master cylinder cap for the square reserviour and a used GM J-35589 adapter for the round camlok cap reserviours.

1992-1994 12 terminal ALDL... I haven't done this on a 1992-1994 GMT400 truck... However... It should be possible on 1992-1994 with a Tech 1, Tech 1A, Mastertech MTS3100, or Tech 2.
The Tech 1 type tools (Tech 1, Tech 1A, and Mastertech MTS3100) all use the same program cartridges.
You'll need the Mass Storage cartridge with full 81-94 GM coverage or the ABS cartridge that supports your truck...
The Snap ON MT2500 may be able to do the 92-2002 trucks with the right cartridges, key, and adapters.


(1995 ONLY) 16 terminal J1962 ALDL/OBD I is possible with the same tools but you need the J1962 OBD II cable interface box and J1962 OBD I cable for the Tech 1, Tech 1A, or Mastertech MTS3100. The Tech2 will handle a 1995 with no problems at all. I haven't tried an MDI on a 1995 OBD I vehicle but you're welcome to try it... It might not work because the J1962 OBD I port is actually speaking ALDL on some of the manufacturer defined terminals and not OBD II.

For 1996 to 2013 rigs that are OBD II compliant you need a Tech 2 or an MDI or VX Diag and Tech2Win on a laptop. There are several OBD II tools that will do this as well such as the Snap ON MT2500.

A picture is worth 1,000 words so how many is a video worth???

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[delta_p]

I read on motor.com "The Nuts and Bolts of Kelsey-Hayes 4WAL" that the F1 functional test to operate the ABS without driving, or to bleed the BPMV, can be performed by jumping the terminals A and H on the ALDL for 2 seconds and removing.

Has anyone done that and it worked?

https://www.motor.com/magazine-summary/nuts-bolts-kelsey-hayes-4wal-june-1998/

 

[hatzie]

That's exceptionally helpful info for the guys with the 92-94 OBD-I and OBD-II 4WAL systems that don't have access to a Tech 1 type tool or a Tech 2.

Another interesting piece of info...

According to the MOTOR article linked in Post #2 you can set the tire size in the ABS controller using a Vetronix Scan tool (Tech 1, Tech1A, Tech 2, Mastertech MTS3100). If that's true it really is a necessary step to perform when you change from the stock tire diameter.
I'm not sure that any of the aftermarket tools will perform this little dance and they weren't clear on whether the 92-94 controllers that are accessed by ALDL were handled in this manner either.
Updating the tire size in the ABS controller made a larger difference in percieved braking performance then I originally thought possible on my 2005 Silverado when I changed from the stock 30.5" 245/75R16 tires to 31.6" 265/70R17 tires... Yes the ABS and PCM tire calibrations are separate on my 2005. The Vetronix tools can't easily modify the PCM revs/mile calibration either I had to go aftermarket for that little dance.

 

[Schurkey]

This thread is titled "92--2002 Kelsey Hayes..."

BEWARE. Some of the information listed applies ONLY to the '92--94 EBC4 controller, not the '95--newer EBC-310 controller. (Other vehicles than C/K have different model-year breaks between the two styles.)

That "Motor" article is poorly written in that regard.

My MTG2500 with 6.2 software WILL NOT activate the ABS bleeding procedure on my '97 K2500 with EBC310 controller. My Solus Pro 8.2 also will not do an ABS bleed on that vehicle (but it will bleed ABS on a 2003 Trailblazer. Go figure.) However, I tried a Solus Pro with 14.2 software, and that will do an ABS bleed on the '97 K2500 EBC310.

 

[bob850]

Hi guys, sorry for the thread revival. I have a '93 K2500 Suburban. I'm trying to find a scan tool that will bleed the ABS on my vehicle (it has the Kelsey Hayes EBC4). If anyone has a recommendation on an affordable unit that will do it, I'd appreciate hearing. I'm also a little confused as to whether a Tech 2 (or equivalent clone) will work on a 92-94 truck, or if a Tech 1 is required.

 

[df2x4]

I'm also a little confused as to whether a Tech 2 (or equivalent clone) will work on a 92-94 truck

A Tech2 will do all GM vehicles from 1991 through 2013, they work fine with OBD1.

 

[bob850]

Thanks df2x4. I went out and tried the jumper trick between pins A and H and it did indeed trigger the ABS unit to activate. One thing I don't understand for sure though. If you want to bleed the EBC4 ABS unit by activating it (like I did with the jumper), do you need to have the valve depressors installed and side screws turned while doing so? In other words, will simply activating the unit (either with the jumper or with a Tech 1/2 tool) achieve the bleed?

Other sources talk about turning the side screws and applying the valve depressors, then opening the two bleeder valves on the EBC4 unit (with someone else pressing the brake pedal), to bleed it like you bleed a wheel caliper. Is this an alternative to the method above, or should it be done in addition to the method above?

 

[Schurkey]

Bleed as described by the attached instructions.

 

[AuroraGirl]

A Tech2 will do all GM vehicles from 1991 through 2013, they work fine with OBD1.

not all vehicles , but 1991 support starts for a few models and it jumps up quickly for 1992(when a lot of models changed generations or had very large revisions)
By the time the late late 2000s and early 2010s happen, it starts to drop support for vehicles which migrated to the GDS2 or MDI or something depending on models and years. My moms 2013 equinox for example is not supported by a tech 2. But thats pretty inconsequential unless someone is talking about a 2008+ vehicle lol/

A obd1 tech 2 use is very helpful if you have a supported vehicle, otherwise a tech 1a and 1 would be needed, which are so hard to come by you would be better off finding old snap on and other make tools that support that era before 1991

 

[SethT]

IS there any reason you can't just manually activate the pump motor by putting 12v to the pump motor pwr pin and ground the GRN pin on the Kelsey Hayes unit for 92-94?