For the problem reading the 94 EBCM, next time try enabling the Comms display on the Comms tab. It may help to see what is being sent and what is coming back (if anything). Also click on "Include idle traffic" to set that on as well. While attempting to scan, I would turn all the other sections off. I see that they were all turned on in your screenshot.

 

Hi Gary,

Thanks for the reply. So what I did was connected up, selected the comms boxes like you asked and set to just scan ABS. I turned key on but did not start. Clicked Connect in app and I got the below message. Previously I clicked scan but at that point I was getting a lot of data so I tried again so I could send you a good screen shot. I got a bad checksum. Seems it isn't able to read from EBCM?

Shutup request----F45608AE----
Shutup request----F45608AE----
Shutup request----F45608AE----

Time=7:31:42 PM
Idle traffic:90 5A 02 00 5E 1C FF 9B 0A 58 FF 00 00 9F F4 56 08 AE F4 56 08 AE F4 56 08 AE F4 56 08 AE F4 56 08 AE F4 56 08 AE
ABS info request-->--F9570105AA----
Response: cs=B6 Bad checksum!
Bad response: F9 57 01 05 AA 00 06 3D FD F5 ED 51 36 59 ED 5D FF FD 55 7D 6B FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 0A 58 FF 00 00 9F 90 5A 02 00 5E 1C FF 9B F0 56 F4 C6 90 5A 02 00 5E 1C FF 9B 0A 58 FF 00 00 9F 90 5A 02 00 5E 1C FF 9B F0 56 F4 C6

 

There appears to be data coming back from somewhere (00 06 3D FD F5 ED 51 36 59 ED 5D FF FD 55 7D 6B) but it's not from the EBCM. Maybe try to unplug the pcm and airbag controllers and repeat the one-time scan. Make sure to remove the airbag controller fuse before doing this.

 

Update to my original post regarding no communication with the EBCM.

I bought an ALDL-USB cable and downloaded Gary's program (thanks Gary!) on a borrowed laptop from work and plugged 'er in. This cable (from Red Devil River) has a removable 10k resistor. I read somewhere that a 10k resistor is sometimes required to read certain speeds of data? I'm not sure. But it would make sense if my Snap On scanner either has a burned out resistor in the GM-1 ALDL dongle, or the cable was replaced at some point. The Snap-On can't read the EBCM, but this cable with Gary's software absolutely can!!!

I've got codes-- 21, 26, 91. 21 and 26 are for Left front wheel speed = 0, and left front wheel excessive speed variation, and code 91 for open brake switch during decel, which I believe may be caused by the first two. Having a passenger watch the live wheel speeds while driving around, the left front is producing an intermittent signal. Hitting bumps seems to knock it on/off line.

So now I'm off to troubleshoot if it's the sensor, or a connection in the wiring somewhere. But at least I'm closer to nipping this one. It's been a long road....

 

Your car doesn't need the 10 k resistor installed on the cable. That's only for earlier OBD1 cars ('92 and older).

Most likely cause of the codes is a broken cable from the chassis to the wheel hub. The flexing for 25 years will do that. Wiggle the cable while watching the scan and spinning the wheel..

 

Thanks Gary. I might swap the front jumper harnesses to see if I can reproduce problems on the opposite side. BUT, figuring I'm into finding at least one new jumper harness....... Does anyone have an idea where I might find one or two of these, either NOS, or reproduction?

Everything I come across seems to be just one connector with 6-9" of wire that you have to splice and crimp. Not exactly what I need.

 

If you have a good connector(s) and the right crimp tool you can fabricate your own, make your desired harness lengths and route them.

 

May this hopefully be the last post.

Since new front wheel jumper harnesses are hard to find, and I didn't want to invest the time (yet) to make my own, I decided to swap harnesses left and right, since they are the same. Well, whaddya know. With the right harness on the left side, the left front wheel is still reading erratic and/or zero. It's not the harness.

That means the problem is between the body-side connector up-to and including the EBCM. Thankfully the LF wheel is the shortest run of wire. Remember, I've got a reman EBCM in there since the original was having other problems.

For the hell of it, and because I can now read ABS faults, I plugged in the old EBCM. It had some fault for rear ABS motor short to ground, which is recurring on that EBCM, but not the new one. The new EBCM has about 500 miles on it, and has never had that fault, so we assume it's just a problem with the old EBCM and not the rear ABS motor. I cleared faults on the old EBCM and went driving for about 30 miles. That's well within the distance that the other (new) EBCM sets a fault for erratic LF wheel speed or LF wheel speed = 0. Kept driving. NOTHING. Jiggled both the connectors around, nothing. No wheel speed faults. Harnesses are good, connections are good.

So... G*D*** it. The new $250 EBCM from Blue Streak is bad. I can't get the LF wheel speed issues to reproduce with the old ebcm, so that has to mean it's a fault with the new EBCM. I've tested resistance, voltage and continuity AT the EBCM connector, all good. So I HAVE to assume at this point that it needs yet another new/reman EBCM.

I've chased my tail on this round and round for 3 months. Is having ABS a big deal? No. Could I ground out the annoying ABS INOP light? yes. My gripe is the fact that I've been unable to find and solve the problem. The car is a survivor, just 17k miles, so I want everything to work as it did from the factory. So here we go again--trying another EBCM? Note: Blue Streak is ****. Absolute ****. But they appear to be the only ones fixing up old EBCM's. They're using the wrong size fasteners on the case, and when I opened their crappy reman unit, it's still using old capacitors from 1993, and a couple on mine appeared to have leaked? at some point. I've got a lead on a used one, so I might go that route instead. Just never know what you're gonna get though with salvage stuff, too.

 

It would not surprise me if a cable that was intermittent became "good" after moving it around or un-pluggin it and re-plugging it. It could be that the connector pins were corroded and you "fixed" that in the process, at least temporarily.

 

I’ve abandoned the idea that the jumper harnesses are the problem, at least for now. Swapping in the old EBCM does not produce any faults for wheel speed variation and the wheel speed does not drop to zero while driving around.

When I swap in the new one, boom, even with the jumper harnesses on opposite sides, I’m getting wheel speed faults for the left front. Opening the EBCM case reveals many solder joints where the 32-way connector seats on the circuit board, so I’m willing to believe there might be crack somewhere in the circuitry for one of the left front hi/low signals. I just have no good knowledge of how to test that stuff.

Autozone accepted the return of the faulty EBCM today and I have another new one coming!

 

If swapping the jumper harnesses did not move the code to the other side, have you considered the possibility the problem may be the wheel speed sensor itself?

 

Yes sir...That was replaced two days ago with a brand new unit from Moog.

The new EBCM should arrive on 10/3. I'm really hoping this is the end of ABS issues for a while.

 

"New" (2nd) EBCM arrived from Autozone / Blue Streak. Absolute f-ing trash. Would not recommend/do not buy.

The original OE computer has an issue with the rear ABS motor shorted to ground. The rear ABS motor is not shorted to ground, because I've tested it, and clearing ABS codes makes it go away, and sometimes it operates normally without setting any codes.

1st "new" EBCM: No codes set for rear ABS motor shorts, ever. However, it kept setting codes for front left wheel speed variation and wheel speed = 0. Watching it on Scan 94/95 sure enough the left front signal appeared to be cutting in and out. So I chased connections and wires, thinking, gee, brand new computer, it's got to be something else. I replaced the front left wheel speed sensor, swapped jumper harnesses left to right. Computer still had issues with front left wheel speed. That's when I got the bright idea, it's the damn EBCM. again.

Just for fun I pulled the case on this "reman" unit apart to have a look inside. First, they use the wrong size fasteners, and not all the fasteners are the same size. Nice. Second, the circuit board looked absolutely trashed, corroded. It's got original capacitors on it with either glue, or leaking solution. Whatever they've done to "remanufacture" it clearly involved replacing a single part and not testing it.

2nd "new" EBCM arrived today. Plug it in. The right front wheel speed sensor is reading anywhere from 1-4mph with the car parked and idling in the garage. Banging on the EBCM influences the reading. Awesome! Tried driving it, wheel speed evens out at speed, but coming to a stop engages full ABS, every time, brake pedal pulsing and wheels pulling. Nothing to do with left wheels, nothing to do with ABS motors shorted to ground. Yet another bad reman unit.

So I plugged in the old OE computer again. No wheel speed codes. Speeds read evenly and uniformly going down the road, no issues there. But of course, it's throwing the code for the rear ABS motor--which clearly isn't an issue, as evidenced by the other EBCM's working in that regard.

Now what?!

 

I've never been in one but if all your replacements have corrosion, then i would think yours might too and the the corroded part might deal with the rear ABS motor. you might be able to clean it up and use your old one.

Its just a thought. i would keep your old one at any rate to be a possible good rebuildable unit. these might be like the opti's hard to find good parts!

 

Last post on this one, I promise. Because I hate threads without a happy ending

I bought two junk EBCM's off eBay. One was from a 93, same part number as the original unit from mine. The second was a NOS EBCM, still in the box, for a 95, without traction control (that's important). To answer the question, yes, a 95 EBCM without TC will work just fine in a 93. Connectors and functions are the same, even though the part numbers are different.

No codes, no faults, wheel speeds are reading evenly, consistently (and most importantly- ZERO when stopped). I put 70 miles on the car between the two computers (swapped mid-way) and both worked absolutely perfectly. I decided to put the 93 computer in, since it's the "correct" one for the car, and I'll save the 95 in case I ever have problems again. It's what I should have done in the first place.

"Case closed"