Would you assume my ABS control module is bad?

[John Livingston]

One way to know which contact on the ABS Main Relay socket (and determine which socket is the ABS Main Relay socket) is #85 and which is #86, is measure for resistance between ABS controller pin 19 and both of them, with resistance being nearly zero between the ABS Main Relay socket #86 and ABS controller pin 19. This is assuming the wire between the two is intact, which I'd assume it at least was at the point when the fuse blew. Hopefully the fuse blowing, saved the wire.

Edit: This is also assuming the wiring diagram and the diagram for the ABS controller connector are correct so you are sure you are testing at controller connector #19.

I got open circuits on three of the sockets, and 0.5 ohms on one.

 

[J_C]

It still looks like the right relay socket is more likely the main relay due to pin 87a.

Those readings suggest to me that the main relay is being triggered on, because then 12V is making it to pump relay pin 85 with ignition on.

With pump relay pin 85 at 12V but 12V not making it to ABS controller pin 17, this suggests a break in wiring or connector fouled between these two points.

 

[J_C]

I got open circuits on three of the sockets, and 0.5 ohms on one.

View attachment 459513

Okay, so the right relay socket is the main relay, and the wire from pin 86 to abs control module pin 19 is intact. I would focus on the wiring I colored red in my prior post.

Edit: I mean take a resistance reading between pump relay socket contact 85 and Control Module connector pin 17. If the wire is intact, and I don't see how it could be without 12V getting to pin 17, there should be a near zero resistance reading.

 

[John Livingston]

Thanks. I'll look over the above. Attached is the relay box photo, with the two sockets indicated, where I inserted 12V, just in case this helps.

 

[J_C]

Okay now I see why the fuse blew. Pin 85 on the pump relay, feeds back to "A" on diagram 42-2, then to "A" on 42-1, to the main relay, and if the main relay is not energized, the power would go in to pin 30 on main relay, and out 87a to ground, with nothing limiting the current except the fuse blowing.

I'm not as certain about causing the pump to run, presumably feeding 12V to pin 86, caused a backwards flow of electricity through the main relay coil, energizing it and putting 12V out pin 30. I don't think it is necessary to jump relay socket pins any longer, just to focus on the wiring in red that I indicated previously, assuming we've got all relevant data now, including the diagrams being correct and the most recent voltage and resistance readings being correct.

 

[John Livingston]

All data from today should be accurate. I had been focusing on the wrong relay yesterday, in addition to the wrong pins the day before!

So, there should be two O/Y wires going to pin 85 on the pump relay, one from the diode, which shouldn't have juice, and one from the ignition switch, which should, provided the ignition is on? Is "S150" a plug/connector of some sort?

 

[J_C]

No power through the diode, I think we can forget about the diode.

The other wire is "A" on 42-2, which goes to "A" on 42-1, which goes through the main relay, which can only be energized with ignition on, AND with the ABS Control Module grounding the Main Relay coil to complete the circuit, with the ABS Control Module needing 12V on pin 20 to do so.

Ignoring the diode, we see on diagram 42-2, that several wires are joined at S150, which should have been feeding the same 12V on Pump Relay socket contact 85, to ABS Control Module pin 17, without even needing the Pump Relay installed to do so. I still think the last diagram I posted with the red colored trace, is where the fault lies, unless the 4WABS Hydraulic Unit has a shorted coil pulling the voltage too low, but I would expect that to blow a fuse, so I would measure resistance between Pump Relay socket contact 85 and Control Module connector pin 17. High resistance or open circuit means a fault in that run between these two components.

 

[John Livingston]

I hope this info I'm about to relate doesn't mean some of my other data is wrong.

I read resistance between the pump relay (the left, or toward-the-radiator relay) socket 85 and pin 17 on the controller connector, and I got .3 ohms. The photos are supposed to show I've got the probes on the correct spots, although I had trouble getting a clear shot of 17.

 

[J_C]

In post #80 you pictured that you were getting 12V on pump relay socket contact 85 with ignition on. Now you are measuring 0.3 ohms between these two points, to control module # 17. I don't see how this is possible, to not have nearly 12V on control module #17 as reported previously, unless there is a break in the wire and by manipulating it, you have temporarily caused it to conduct again.

... unless of course, the wiring diagram isn't correct, but even then, it wouldn't make sense to have 12V then 0.3 ohms to next point in circuit (and some of that 0.3 ohms may even be due to the meter probes not the circuit) and not have near 12V there too.

 

[John Livingston]

I rechecked and still zero volts at pump relay 85 with the key off. Roughly 12 (more like 11.5) volts with it on. I then rechecked 17, with the key on, AND THERE'S 12 VOLTS!!! This is the first time I've measured volts, under any circumstances, at 17, so, it does seem like there's a loose connection. I may try to plug in the relays and reconnect the controller, to see if the ABS light is off. I think it has to cycle a few times, so I'll shut it off and on some. I was definitely stretching/bending the wiring significantly, to get the last couple of photos, so maybe that did something. Few things are worse than an intermittent problem. If I get it reconnected, I'll see if the code readers see the ABS now. This may have to wait until the morning.

 

[John Livingston]

I plugged the connector back into the ABS controller. I did not tighten the bolt that holds it in place, but it seemed snug. Still have the ABS dash light on. That may be an old fault, of course. I did try connecting the Innova reader. I got several screens, indicating to me that it had the proper connections and protocols to ABS on this truck (the first photo, which was taken after it had done the regular OBDII checks, and I asked it to check ABS(, but eventually it again failed to communicate.

What I found very peculiar was that, while testing 17 and getting 12V, I inadvertently got into 16 and got 12V there! The manual says that's an ISO 9141 Link. I swear, like 17, I hadn't gotten 12V there before, although I didn't test it as often as I had 17. I put more light on it next time, and make certain I'm not somehow touching more than one pin at a time.

Between some traveling and weather, it may be a few days before I can do much else. I'd like to track the O/Y wire to the controller plug and see if I'm still getting 12V with it connected. I'll double-check 16. I may go back and check all active pins for 12V, just to see if there are any other anomalies.

 

[J_C]

I don't know about the compatibility of your scan tool. That's a major snag in figuring out what is going on with the ABS. I do recall that once on my '98, I had pulled a fuse that supplied power to my (different pinout) ABS controller, which made the ABS light come on (but the ABS light had never been coming on prior to pulling the fuse), and the light stayed on after I had put the fuse back in.

Whether the light would have eventually reset itself after some driving or power cycles or not, I don't know for certain because right away I used a BAFX ELM327 based dongle and Forscan app to clear the code, then the light went off immediately. Since your ABS module is different than mine, I don't even have 100% confidence that being able to pull codes with the BAFX on mine, would work equally on your vehicle... "probably", unless the ABS module still isn't getting power and this prevents setting a specific code that is relevant.

I don't know what to make of your voltage reading on pin 16. If you don't find the fault soon, it might be time to risk pulling more things apart like getting the relay box unfastened and take the back cover off, start gently pulling looms off the wiring to see if you find a fault through visual inspections, but first I would look at any exposed areas of the wiring in case there was chafing, insulation failure, or rodent damage.

 

[John Livingston]

Back from my trip. Checked pin 17. Back to zero volts. I tried twisting, pulling, and pushing on the harness to see if I'd get momentary power, but nope. I then put in a tap on the O/Y wire, just before it goes into the connector. Had continuity between the tap and pin 17. Ran 12V to the tap from the battery's positive terminal. Another 10A fuse immediately fried.

As a last effort, before I give up and put antique tags on the heap (which, in VA, means I won't have to pass state inspection), I'm tempted to cut the O/Y wire, within a few inches of the connector, and see if running 12V into it, without a backward connection, still blows the fuse. I hate to cut that wire, but it's not like it's doing me any good in one piece. Before I do that, I'll see if there's ground at pin 17, with the ignition off. Seems like that would point to a possible short.

It certainly is possible rodents chewed something. I've found a little evidence of mice, in the form of acorns eaten and some insulation appropriated, but minimal. I'll try to trace the harness back to the firewall, and see if something's damaged.

Then again, if there's a short somewhere, you'd sure expect to find a blown fuse.

 

[J_C]

Edit: I'll leave what I wrote below, but remember, as I mentioned in my next post #97, that the orange/yellow wire and pin #17 on the Control Module should be shorting to ground when the ignition is off and the ABS Main Relay is installed.

Yes I do wonder if that wire is severed and the end making it to #17 is shorting out, but I thought at one point you did get 12V at control module #17? This topic has had a few twists and turns and I am not sure that I remember what is true and not.

I agree that cutting that wire, or getting into the back of the relay box to do it, is something I might try next, and I would also wonder if there might be a shorted out hydraulic unit coil, so when you put power to #17, possibly it is trying to activate the coils so then is when it blows the fuse, and yet I would have thought it would have also blown a fuse normally on that circuit (#9? The one at the top left on diagram 42-1) as that is where the coils should have gotten power from.

Another thought is what is the amp rating of the fuse you are putting on your test wire? I don't know how much current this circuit needs, but fuse #9, best that I can make out from the diagram is that it's a 30A fuse (or maybe 20A?) so if you were substituting a lower amp fuse, possibly the circuit just needs more current than the fuse you chose? Then again if you are blowing fuses, I hate to suggest using larger and larger fuses as this causes even more stress on wires/connectors/components if there is a fault. I would check resistance to ground on #17 as you mentioned.

 

[John Livingston]

I don't blame you for being a bit confused! I did see 12V at 17 last week, just before I headed out of town. It was the first and only day I got 12V there, but I checked it several times that day, and it was good. It is no longer showing any voltage, as reported above.

I thought 17 was fused at 14, on the side of the dash, which is 10A. I'll try to determine if I'm wrong about that before cutting anything.

 

[John Livingston]

I looked at the two wiring diagram pages you folks nicely provided (42-2 and 42-3) and wasn't able to determine which fuse was relevant, but that might just be me. I checked to see if circuit 532 (O/Y) was grounded (using the tap I'd inserted near the controller connector), with or without the ignition switch being on, hoping that, if it was, I could pull fuses until it was an open circuit, but there was no resistance.

 

[J_C]

Fuse 9 (?) is relevant.

The power flow is battery to power distribution box fuse 9 (? top left on diagram 42-1), through the ABS main relay when activated by the ABS control module, out pin 30 of the ABS main relay, to arrow "A", to arrow "A" on diagram page 42-2, then at the ABS pump relay, splits off to junction S150, where one of the spits goes to ABS control module #17.

Remember what I wrote previously, that you aren't supposed to have 12V on pin 17, unless the ignition is on, which is what toggles the ABS main relay from shorting to ground, to supplying diagram 42-1 arrow "A". Thus, if you put 12V on the orange/yellow wire or pin 17 while the ignition is off, and the ABS Main Relay is in the socket, it is expected to, SHOULD be shorting it to ground which would blow the fuse on your test lead. Also if you put 12V on the orange/yellow or pin 17, and for some reason the ABS control module is not toggling the relay from the shorted to ground state, to the making contact between pin 87 and 30, then again it is still shorting to ground.

You need to make sure that every wire as shown on the diagram, has low resistance between each two points, and that none are shorting to ground that shouldn't be. Orange/yellow should be shorting to ground when the ignition is off and the ABS Main Relay is in the socket. Sorry that I forgot about that in my prior reply, which I have prepended to include that info.

 

[410Fortune]

Do you want me to ship
You a known good 96/97 abs control module? I’ll send it to you for the cost of shipping
I have three 96 v8 trucks outside two both still run and drive with high miles the other was wrecked pretty good at 150k miles. I don’t need the abs modules and would
Gladly donate one after all of this

 

[John Livingston]

Do you want me to ship
You a known good 96/97 abs control module? I’ll send it to you for the cost of shipping
I have three 96 v8 trucks outside two both still run and drive with high miles the other was wrecked pretty good at 150k miles. I don’t need the abs modules and would
Gladly donate one after all of this

Thanks so much, 410. It's hard to turn down an offer like that! I'm hoping to test for continuity on a few sections of the O/Y wiring. Let me get that done, and I'll report back. It's turned cold by my wimpy standards, so it may be a couple of days.

I need to whittle down my heap fleet. I've got a '03 Outback that's certainly more presentable than the Monty, but so much of the Monty just works better for me than the Subaru, I'd really prefer to let to let the Subie go. I've yet to have a vehicle cross the 200K mile landmark, and I think I'd be happier doing that with the Mountaineer. And this has to be the best forum, among many different ones I've used over the years, I've yet to encounter!

 

[410Fortune]

Subaru needs to go
They are a money pit at high miles and a pita to work on

Not one of our vehicles are under 200k most approaching or over 300k now lol

I like your priorities! Parts are here if you need them I always have v8 lying around I collect as many of them as I can