Author Topic: Why is my ABS MIL on? (Most common causes?)  (Read 4164 times)

DR1665

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Why is my ABS MIL on? (Most common causes?)
« on: June 06, 2018, 01:13:36 PM »
The Short Question
What are the most common issues triggering the ABS MIL on gen 2.5s. (CA-spec, if it matters.)

The Backstory
Fezzik has been deemed a total loss. $4,500 in repairs estimated on a vehicle appraised at (a very fair) $2,700.

In order to get that sweet insurance company dosh, I have to provide a branded (salvage) title. Fine. This will be my fourth old Mitsubishi in a row to be totalled, and my third restored salvage vehicle. No big deal. The problem is, salvage vehicles are not legal for highway use in Arizona. The minute they issue the salvage title, my registration is null and void.

So here's my smart-ass master plan:
  • Take a full day off work.
  • Get in line at the DMV. Get the salvage title. Fezzik, out in the parking lot, is no longer legal.
  • Get back in line for a Level III inspection to get the restored salvage title. Email pictures of salvage title to adjuster.
  • Get back in line for restored salvage title and reinstatement of my registration.
  • Get paid before I (legally) drive Fezzik home.

But considering Level III is the most anal retentive of inspections in Arizona, I need to be 110% gun-in-the-face sure Fezzik will pass any/all roadworthiness and safety checks. I've got a small #todo list, but the ABS light came on the first drive after the wreck and I'm a bit limited on troubleshooting in this area.

My brakes are "okay."

I replaced the front pads two years ago. And I replaced all four guide & lock pins on the front calipers last summer.

I also replaced the rear pads last year, and those started squealing heinously within a month. (I know, Ryan. I know. A complete overhaul is at the top of my list with that insurance money. Rotors, pads, shoes, cylinders, fluid, speed bleeders, and manual effing hubs while I'm in there. Wo0t!)

When backing up, my rear brakes will randomly sound like there's a rock scraping a shield. Every. Time.

About two months ago, I was braking as I entered a center-divide left turn lane and one of the tires hit a making-America-great-again pothole. The pedal went right to the floor and the ABS light activated as it did its crappy, 90's-era ABS modulation song and dance. I had to release and re-apply the brakes to actually stop.

Considering this truck went 160k+ on the original timing belt, either had the original transmission fluid from 1998 OR straight motor oil in it, and has obviously had collision damage repairs which did not show on a spotless Carfax report, I wouldn't be surprised to discover I'm running the original rotors and some part of the all but worthless rear drum brake components has finally completely worn out.

But could the ABS light be on simply due to low brake fluid? (I'll check the level tonight.)

Could I easily identify issues with wheel sensors without removing the tires? (It's hot. They're dirty. And I've easily spent 80 hours dealing with truck bullshit in the last 30 days.)

Any other advice from the OGs?

Thanks in advance. Y'all make these trucks even better.
The Driggins | 98 Pajero | 11 Juke
(Previously: 89 Pajero 2.6, 92 GVR4, 91 GVR4, 97 Talon)

Shovel

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #1 on: June 06, 2018, 01:21:16 PM »
Any chance that Corolla you parked on top of came into contact with the rear wheel speed sensors?

concealer404

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #2 on: June 06, 2018, 01:26:04 PM »
In for fix for heinously squealing rear brakes.  Mine are fine until i put some decent heat in them (coming to a complete stop from highway speeds), then once i get moving again, it's pain for everyone's ears within a 1 mile radius.  Truck stops fine.

Brake light is on at least 50% of the time.  No leaks, brakes work great.
1998 Montero Winter Package (For Sale)
1994 FZJ80 Land Cruiser (Wife's)
2006 V8 4Runner Sport Edition (Mine)

DR1665

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #3 on: June 06, 2018, 01:35:22 PM »
Any chance that Corolla you parked on top of came into contact with the rear wheel speed sensors?
Yes. Any chance damage would have to be obvious to trigger a malfunction?

Aren't they, like, Hall Effect? (Meaning, "if they look correctly installed/intact, they should function"?)

In for fix for heinously squealing rear brakes.
Dude.

With mine, they're silent until they warm up. I can silence them by being more aggressive and applying more pedal more rapidly, but yeah. Sometimes I find myself modulating pedal pressure in traffic to have them sing along with the radio. Pedal isn't the firmest I've ever driven, but I've no reason to be concerned. I'll regularly do extended downhill runs north of 75mph with frequent speed corrections in the corners and have no doubts they work.

Seems to be the rear squealing though. And that scratching noise, if it matters, only seems to happen once per revolution in reverse, or twice backing out of any given parking space.

Thanks, gents.
The Driggins | 98 Pajero | 11 Juke
(Previously: 89 Pajero 2.6, 92 GVR4, 91 GVR4, 97 Talon)

Shovel

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #4 on: June 06, 2018, 02:22:25 PM »
Any chance that Corolla you parked on top of came into contact with the rear wheel speed sensors?
Yes. Any chance damage would have to be obvious to trigger a malfunction?

Aren't they, like, Hall Effect? (Meaning, "if they look correctly installed/intact, they should function"?)

Yes they are Hall effect,  it's an energized coil (like a metal detector) and the teeth passing in proximity to the sensor makes a tone.     I don't know the exact number of teeth (there are also small and big tone rings, depending on year) but let's say 48 teeth,  at 50mph with a 31" tire the wheel is turning 542rpm and the sensors are reporting a 434hz tone.     The brake controller is going to frequency delimit this to ignore frequencies way out of range (for example you'll never be going 175mph so the controller can safely ignore 1.5khz tones and above as noise..) and it's also going to ignore speed differences small enough to account for wheel speed variations around corners (our Monteros don't have steering position sensors and the airbag motion sensor is not connected to the ABS) .       

That means that (with regard to the ABS sensors) things it will NOT ignore are a 0hz "signal" (resistance present in sensor but no movement apparent),  an open circuit (mechanically damaged sensor or wire or connector),  and also induced frequencies that are within the pass range of the frequencies it can "hear" - in other words, if something is inducing a 700hz frequency (vibrating dust shield...) it could falsely inform the ABS controller that wheel is going 100mph when it's not.   

So check your sensors for mechanical integrity, check their wiring, disconnect each one at its wiring connector and measure DC resistance across the terminals (I don't know the correct resistance value right now, but it's going to be greater than 0 ohms and almost definitely less than a thousand.    If you measure all four and one of them is meaningfully different from the other 3, you're onto something.

Also while you've got the sensors out of their holes inspecting them for mechanical damage,  clean the shyte off the magnet ends and use a penlight to inspect the tone rings if you want to do a thorough job. 


Shovel

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #5 on: June 06, 2018, 02:34:59 PM »
Oh.. also.. I bet you know somebody who owns a MUT..

If your transfer case or front axle 4wd position switches aren't reporting the same thing that the ABS thinks should be happening you'll also get an ABS MIL - for example if the transfer case position sensor thinks you're in 4H but your front axle isn't engaged (enabling an averaged difference between the front wheels and rear wheels..)

Crumb

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #6 on: June 06, 2018, 03:00:28 PM »
Oh.. also.. I bet you know somebody who owns a MUT..

If your transfer case or front axle 4wd position switches aren't reporting the same thing that the ABS thinks should be happening you'll also get an ABS MIL - for example if the transfer case position sensor thinks you're in 4H but your front axle isn't engaged (enabling an averaged difference between the front wheels and rear wheels..)


 God damn! Emperor of Monteros! Yeah, what Shovel said...


 Come get your ABS scanned and i'll give you that engine dipstick you have sitting here.

DR1665

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #7 on: June 06, 2018, 03:23:08 PM »
Oh.. also.. I bet you know somebody who owns a MUT..

If your transfer case or front axle 4wd position switches aren't reporting the same thing that the ABS thinks should be happening you'll also get an ABS MIL - for example if the transfer case position sensor thinks you're in 4H but your front axle isn't engaged (enabling an averaged difference between the front wheels and rear wheels..)


 God damn! Emperor of Monteros! Yeah, what Shovel said...


 Come get your ABS scanned and i'll give you that engine dipstick you have sitting here.

I'm not worthy to quote Master Shovel. Damn. That was next level and a half, mate. I DEEPLY appreciate the additional context and insight. That's as solid an answer as any I've ever received on any forum in 20+ years. Thank you.

Interestingly enough, I have the crumbly ball tcase shifter installed—Kevin Roy hooked me up with the good one, just have to install it—and often get my 4H lights blinking randomly while driving. Happens almost daily.

Looks like I'm gonna just have to fix EVERYTHING else on the truck and be one of those 100% reliable guys nobody likes. :P

@Toasty, I'll ping you for your location and make arrangements to pay you a visit. Thank you.
The Driggins | 98 Pajero | 11 Juke
(Previously: 89 Pajero 2.6, 92 GVR4, 91 GVR4, 97 Talon)

JohnnyBfromPeoria

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #8 on: June 06, 2018, 05:02:05 PM »
Shovel, that was the best damn ABS-planation I've ever read.

Brian, nobody doesn't like the guy who has the truck where everything works right. I mean, we like Shovel, don't we?

John B.
AZ Crew/East Sider/Former 14th St Crew
95 SR, 35x12.5-15 on 8" steelies, 2" BL, stuff cut off, stuff welded on, lights, sound, front ARB pending
87 Raider, There's a turbo 2.6 under its hood, really
83 "Dodge" Power Ram 50, a bit lifted, way slow and gets more comments from random people than the other two put together
'95 Montero SR. Pretty much stock, Trail Gear Sliders, ADD skid plates, Stereo by Shovel, Timing maintenance by Pa_Jero

Shovel

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #9 on: June 06, 2018, 07:52:16 PM »


Interestingly enough, I have the crumbly ball tcase shifter installed—Kevin Roy hooked me up with the good one, just have to install it—and often get my 4H lights blinking randomly while driving. Happens almost daily.

Looks like I'm gonna just have to fix EVERYTHING else on the truck and be one of those 100% reliable guys nobody likes. :P


It's pretty likely that this is your culprit - but check everything else anyway.   

Also clean a little inside the area where the shift fork lives, then after you're done change your transfer case lube.  You got ball crust in there. 

C'mon man AZ crew can be the LAND OF GLEAMING MONTEROS THAT RIDE ETERNAL SHINY AND CHROME!!! 


Crumb

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #10 on: June 06, 2018, 08:57:34 PM »
 Dude! You got new wheelios!

RyanY

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #11 on: June 12, 2018, 03:32:30 PM »
You can pull ABS system codes without the MUT2 to find out what is causing it's confusion. On my 95 you jump a connector near the ABS pump and read the flashing codes on the ABS light - your system is probably different being newer and all, consult your friendly neighborhood FSM for procedures specific to your year. :)

Rear brake noise when backing up is probably in the parking drum brake system - a spring out of place or something silly like that. I'd try adjusting the parking brake shoes first and see if anything changes.

Brake squeal can be such a pain to diagnose sometimes - most often it's glazed pads or rotors, but I've seen sticking calipers and slider pins cause it also. It goes without saying that you need to have all the fun little pad locating clips in place and the anti-squeal shims on the backs of the pads (integral with most pads anymore but some cheap brands don't have them).   

PajEvo

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Re: Why is my ABS MIL on? (Most common causes?)
« Reply #12 on: June 12, 2018, 11:27:36 PM »
Pulling the codes, via MUT, Flashes, or EVOSCAN is just so nice and easy. Well, pulling the codes is. It may still require some digging of course. On my EVO4 right after I imported it we discovered ONE tooth on the ring was flattened down. Still there, but flattened against it's neighbour. Hours and super careful application of JB weld later, the ABS light was gone, and I passed my inspection the next morning.

I guess what I'm saying is start with codes, but don't be afraid to get dirty details, depending on where the code sends you.