Kelsey Hayes EBC310 Diagnosis - Error Code 68, 73, 86

[fancyTBI]

Vehicle: 1995 C2500 (8600gvwr) with 4WAL.

Issue: Air trapped in ABS module, cannot bleed via scanner (Snap-On Solus Pro with ver. 17.2 software), DTCs present, can't bleed with DTC's present, scanner displays 0 codes, jumping terminals A & H displays codes.

Codes:
Code 68 - Locked motor or shorted motor circuit in BPMV - sets ABS to OFF
Code 73 - BPMV memory error - sets ABS to OFF
Code 86 - Shorted ABS indicator lamp - sets ABS to ON

When I replaced my brake lines last year I foolishly let air into the system. At the time I did not think much of it because I had a snappy, surely I could bleed it. I attempted to bleed the system (November 2023) but the scanner would not complete the test. When checking the scanner for DCTs there are 0 present or stored. After that I took it to the dealer and they were not able to resolve it. All they did was say "code 68 can't bleed." I thought they would have success with one of their Tech2 scanners, no further diagnosis was performed.

Flash forward to today. I need to get this fixed by 4/15 so I can start driving it. I began looking at 68 first since that was all I had initially. I have 12v power at the 2 pin connector for the BPMV. I noticed that my ABS light was not on, so I diagnosed this - broken bulb. Replaced that and the light follows "normal" bulb check routine. Key on, ABS light turns on and shuts off after 2 seconds. The FSM states that certain DTCs may not trigger the ABS light to stay on. I think the DTCs that set the ABS to OFF would keep the light on.

I will try to manually clear the DTCs tomorrow via the ALDL port without the scanneer. I need to get my battery on a charger over night.

Attached are pages from the FSM with relevant information. Any help is appreciated. I would prefer to keep this system in place. I've also tried the bleeding procedure via pressing the plunger on the unit and that didn't help.

Attachments: Code list, circuit diagram, 67-68 description, 67-68 diag steps. The remainder are in post #2

 

[fancyTBI]

Attachments: 71-74 description, 71-74 diag steps, 86-88 description, 86-88 diag steps.

I've got a decent multimeter that I just bought today. I'm willing to learn and solve this issue correctly. Removing it is a last resort if I am unable to resolve this without taking a gamble on another used unit.

 

[Schurkey]

Vehicle: 1995 C2500 (8600gvwr) with 4WAL.

Issue: Air trapped in ABS module, cannot bleed via scanner (Snap-On Solus Pro with ver. 17.2 software), DTCs present, can't bleed with DTC's present, scanner displays 0 codes, jumping terminals A & H displays codes.

Surprised that the Solus Pro won't display codes. Mine do--8.2 and 14.2, '97 K2500 8600GVWR.

Are you getting ANY ABS info? Wheel speeds, for example?

Codes:
Code 68 - Locked motor or shorted motor circuit in BPMV - sets ABS to OFF
Code 73 - BPMV memory error - sets ABS to OFF
Code 86 - Shorted ABS indicator lamp - sets ABS to ON

Clear the codes, see what comes back.

I took it to the dealer and they were not able to resolve it. All they did was say "code 68 can't bleed." I thought they would have success with one of their Tech2 scanners, no further diagnosis was performed.

This seems unreasonable for a dealership.

I will try to manually clear the DTCs tomorrow via the ALDL port without the scanneer.

I don't know how to do that.

I need to get my battery on a charger over night.

Good idea.

I've also tried the bleeding procedure via pressing the plunger on the unit and that didn't help.

That's not surprising. Didn't do anything on my '97, either.

Even if it did, it's not really bleeding the ABS, it's bleeding the combination valve for the front brakes.

 

[fancyTBI]

Surprised that the Solus Pro won't display codes. Mine do--8.2 and 14.2, '97 K2500 8600GVWR.

Are you getting ANY ABS info? Wheel speeds, for example?

No ABS info on the scanner. Can't test on the road for wheel speeds with how poor the brakes are. It also won't display the brake pedal status of ON or OFF. Will pass the initial communication "test" and bring up the diagnostic menu. When I display codes it says there are none.

I charged the battery finally and had the charger connected during testing to maintain voltage. I went through the diagnostic procedures for code 68 again and the results were the same (this time with a fully charged battery). Connecting leads from the battery to the motor directly with the key on resulted in nothing - no motor engagement, noise, anything. The FSM states "replace the assembly." I noted that the diagnostics also state that most faults are caused by poor connections. But jumping the motor directly sort of eliminates that, yes?

Today I also have the brake light on, which has not come on previously. Of course the brakes are incredibly soft due to the air trapped in the module. I assume the two are related. I suspect this issue with the ABS has always been present. The ABS light has never cycled since I've owned the truck. I just realized this the other day. The bulb was blown out. I am wondering if it is worth while to pick up a Tech2 clone to try out.

Clear the codes, see what comes back.

Unable to clear them via the ALDL port. Method attached. However Today only code 68 is present. I am suspecting that the near-dead battery was to blame for the other ones.

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[fancyTBI]

I should add that I just ohm'd the motor pigtail and i've got 60ohms. Per the manual if it is greater than 1ohm there is something wrong inside the unit. I am not going to go through the hassle of trying to track down a unit that matches my truck perfectly. I have a combination valve off an older truck that I will verify will work and I'll go from there. Guess this is next weekends project.