ABS Light on 92 K5 Blazer

[MI0706]

crabtruck: I wasn't able to do a lot of wiring investigation last night (life got in the way last night, err, I should say the wife got in the way last night.. lol...)

When I jumpered A-H on the DLC, I did not hear the ABS motor pick up.

It's funny that you mention the "add in" of a trailer brake controller. It appears that I have additional wiring running from front to back that would appear to me like it is trailer brake wiring (looks like the wiring is #12awg). This is definately an after build add in.

Anyway, the wiring doesn't connect to anything on either end. The front end is coiled up in some wire loom (conveniently coiled up by the ABS unit). The other end at the hitch is taped up.

If it would make things easier for you, I can take pictures of anything you would like to see. Just let me know if you need to see anything.

I will try to continue tonight and post results here.

Thanks for the help.

[crabtruck]

Take your time, I spent the day tearing down and rebuilding my furnace.
Was expecting temps to drop way down into the low 50's.

[MI0706]

After finally getting home from work (tire blew on the trip home ), I was able to do some more trouble shooting.

First, I believe I read the one of the flashing codes wrong. It's not code 68, it's code 86! Big difference. I also saw another code that I don't think came up the other day, code 81. So now, I'm seeing codes 13, 25, 81, and 86.

On with what I found. As for the CC, I verified the linkages. Everything there seems in good shape. I found that two of my wires on the brake switch go to pins A and D on the CC connector. I ohmed those wires out and the wiring appears to be good (0.2 ohm each). I tested to see if the brake switch opened/closed at the CC connector. I found that the brake switch always says open whether the brake is applied or not. This leads me to believe that my CC problem is there. Unless you think there is another problem somewhere?

As for ABS, when was I finding that I previously misread the codes, I checked to see what happened to code 13 with the brake applied, not applied. Code 13 stayed with and with out brakes.

It appears that two wires on the brake switch go to the 10 pin connector on the ABS unit, pins B and C. I checked the wiring and found that one of the wires checked out fine (0.2 ohms), the other wire was reading a high resistance (296 kohm, yes, 296,000 ohms). So, I have a broke/partially broke wire there. Anyway, for fun, I tested the brake switch operation (open/close) at the ABS connector. It read open all the time (when it should've read 296 kohm because of the bad wire). This leads me to believe that the brake switch is bad and also I have a bad wire.

Checked the speed sensors (ohm reading). Found that the right speed sensor was 2.3 kohm. While the left speed sensor was 175 kohm. I need to replace the left speed sensor. Should I look at replacing the right speed sensor as well?

Also checked the voltage at the ABS unit. It is getting 12 volts.

A rehash for the ABS unit codes:
13 2wd brake operation
25 left front speed sensor
81 brake switch circuit shorted or open
86 shorted anti-lock warning lamp

So to summarize, and please correct me if I'm wrong, it looks like I have to replace the brake switch, fix one of the wires from the ABS unit to the brake switch, and replace the left front speed sensor. Should I worry about ABS code 86? And what do I do about about ABS code 13?

Thanks for the help crab!!! BTW, buwahahhahahhaha... low 50's. Right now in Indiana, the low 50's feel pretty good!

[crabtruck]

Replace left sensor, right is judgement call.
Should cure the ABS light on drive problem.

86 (for now) the 86 code since may be dragged in by other conditions.

Go after the brake switch, I think someone re-wired it.
You have that 296k ohm read - it may not be bad wire,
but rather a resistance through another path. Only can be
sure of the reading when wire is disconnected at both ends.

Unplug CC mod, ABS mod and brake switch.
Then map which wire is actually going where by positive
identification of both ends. note colors and pins.
Sounds like a butcher was working by the brake.

It is near impossible for me to get into my own brake switch
due to other things added there and my advanced age is
ganging up with my general inflexability. But we will try
to get this figured.

Tire sounds like a murphy's law kind of deal.

[MI0706]

crabtruck: My profession is electrician (should've stated that earlier), and when I checked the wiring, that is how I did it. I had the connectors unplugged at the ABS, CC, and brake switch and went end to end with my DMM.

One thing that has struck me as funny is how the brake switch is wired. Two wires on a separate connector for the CC. That makes sense to me. The other four wires are on one connector (ABS and brake lights). Those four wires on the same connector (I wouldn't have designed it that way, but still not a bad thing). What I don't understand is how the wires are laid out on the 4 wire connector. Pins A and C are for the brake lights and Pins B and D are for the ABS. If this were my design, I would've grouped those connections together like what was done with the CC (i.e. brake lights A and B, ABS unit C and D).

Anyway, thanks for the help. I will order another speed sensor and brake switch and post the results here.

[crabtruck]

Cool that you know wires, my caution comments can be
included for other readers without the background.
I think the 4+2 switch setup was because of design add-ons.

Factory drawing shows (and I have found many errors with those)
4-wire: A=Org to Stop fuse, B=YorW to CC pin"_"
..........C=Pk/Bk to ECM fuse, D-Ppl to CC pin-D
2-wire: A=Gry spliced to wire from switched side of CC "on"
..........which goes to CC pin-A
..........B=Brw to CC pin-D
That's a redundancy of function for 2-wire A and 4-wire D.
It also puts one too many wires at CC mod.
Shows A/B as NO and C/D as NC.
Shows A/B 2-wire as NC
ABS drawing shows C/D as NO to ABS pin-C on 10-wire.
Stop drawing agrees 4-wire B is NO and to CC as Wht.

Drawing shows the brown wire from 2-wire brake switch
goes to CC mod pin-D, on my 94 it's purple and behaves
as if coming from 4-wire pin=D

There was a recall for polarity mis-wired brake switches
around that year, I'll see if I can find the details.

[MI0706]

crabtruck: Well, it has been my experience with wires, when checking continuity (resistance), the wire should be 0.1 to 0.2 ohms. Well, I was reading 296k on the purple wire. I thought for sure that wire went directly back to the ABS unit. Well that is not the case. The brown wire goes directly back to the ABS unit (verified with meter).

So, before I started to cut and splice and reroute wiring, I decided to do a hand of hand run down of that wire. Good thing I did. Because that wire comes off of the brake switch and goes up in to the dash! BTW, do you know how hard it is to get the factory original tape off of the wire looms?

As far as wiring trace downs, that is where I stopped. I did some other troubleshooting though.

I jumped the brown and purple wires on the brake switch and checked for codes at the DLC. Within a few seconds, my ABS motor picked up for about a second (first time I've ever heard it run) and my code 13 changed to a code 12. I was still receiving codes 25, 81, and 86. So for now, I've got a new brake switch and left front speed sensor ordered (AC Delco) which should arrive on Tuesday. I will install those and go from there.

One of your previous statements about a butcher doing wiring on the Blazer previously, well that is the case. While I was in checking all this, I found a relay panel that was shoved up underneath the dash. Traced those wires out and the panel went to nothing. However, there were wire splices for this thing all underneath the dash. It appeared to me that at one time the Blazer had a remote start / alarm system on it. Needless to say, all of that **** is gone. Now, under the dash, it doesn't look like a rats nest anymore!

I will let you know the outcome of the CC system and ABS system once the new parts arrive. I should be able to install them and test the same day as their arrival.

Thanks for all the help, I do greatly appreciate it!

[crabtruck]

On the full drawing the CC contacts read
across as A,(1),K,(2),F,h,E,D,C,B,J (that's 11 points)
I believe: A,(G),K,(-),F,h,E,D,C,B,J (that's 10 points)
Difference between (2) and D is which fuse supplies hot
as they functionally send the same info.
(2) is labeled as purple, D as brown. D brown is what I have.

That drawing shows the 6-wire switch but the only
difference between that and the 2+4 drawings I have
is physical, F-E was the 2-wire before.

This shows the (1) or (G) wire as Yellow to sw "B"
but I think it's white on your blazer.

Have any maps to post yet ?

[crabtruck]

Here the drawing on 95 which is more like it I think.
The only dispute I have with it is that the F-E part
of switch should be N/O not N/C, rest looks right.

Note that the clutch is also backwards IMO
but for you, luckily, is N/A LOL

If you have any pics yet, post those also.

[MI0706]

crabtruck: So, I was able to replace the brake switch and left front speed sensor and now the ABS and CC both work (CC works with the exception of the light on the dash coming on... LOL...)

I do not have anymore trouble codes on the ABS system. That is good news.

I did some wire tracing and this is what I came up with:

Brake Switch:
4 wire portion:
Pin A : Brown wire, goes to ABS Pin A. Hot with key on.
Pin B: Purple wire, still not able to trace this wire
Pin C: Orange wire, from fuse block. Hot at all times.
Pin D: White wire, goes to brake light wiring harness.

2 wire portion:
Pin A: Brown wire, goes to CC Pin D
Pin B: Gray wire, goes to CC Pin A

Anyway, thanks for the help. Now I have a functioning ABS and CC. Now on to the next problem... (Does it ever end? LOL)