Blown EFI Fuse and weird Anti-lock brake system problem

[Mike6158]

As I was coming in to Silverton, CO earlier today I had my foot lightly on the brake pedal to slow down on the slight grade that is there. All of the sudden the right front locked and released followed by the right rear locking and releasing. I chalked it up to hitting an ice patch even though it was too warm for ice and the road was dry. I saw a "shiny spot" on the road so I figured it was ice.

Later, coasting down hill, both feet on the floor, the left front and then the right front did a kind of brake lock up switch.

Further down the the right front did it one more time, again coasting down a hill.

Since I've been running some trails and dirt roads all week I ran the LC through a car wash with underbody spray. The thought was that something was going on with the anti-lock brake system.

100 miles later... no more locking up.

But...

I stopped for gas just after crossing to NM from CO. Fueled up. All is good. Hit the key and the engine spun over like crazy but wouldn't start. It was either a no fuel or no fire problem. No codes. I plugged in my scanner and it wouldn't even read the ECU. I was really afraid the ECU had died. In hindsight I probably didn't set the scanner up right. I popped the hood, pulled the fuse cover, and looked at the fuses. There was a 20A fuse labeled EFI that was black on one side. It wasn't just blown... it was fried. I replaced it and the LC started right up. I haven't had any problems since

Any ideas?

 

[Mike6158]

Nothing??

The blown fuse never reoccured. I put 1,200 miles on after I replaced the fuse and never had a problem.

I'm still scratching my head about what could have cause the wheels to lock. It happened without braking and on downhill slopes. The last instance was on dry road north of Durango. The road was in bright sun and it was in the low 70's. The "wiggly car" traction control light would flash and then go out each time. After running it through a car wash the problem seemed to go away. But what would cause the brakes to actuate without pedal pressure?

My "normal" place to explore is down in Big Bend. When I changed the diff fluid I went to a little heavier grade. I used Amsoil Severe Gear 75-110 vs 75-90. I wonder if there's something going on with the diff? The oil analysis came back great on both diffs, the xfer case, and the engine. It was colder when the lockup problem happened but it wasn't cold.

The cruise control drops out on long downhill coasts. It's been happening infrequently but yesterday it dropped out 20 or 30 times. Sometimes the road was rough, sometimes in a curve, sometimes the road was smooth. Nothing consistent. The "wiggly car" light didn't come on. I wonder if the locking brakes and dropping cruise control are symptoms of the same problem

 

[TXLX100]

Well since it sounds like you suspect issues all over the spectrum, my first inclination is that you might have had water intrusion into your fuse box. Has your windshield been replaced or any other significant repair or event before the issues started happening?

Did you find out if you had any pending codes for the brake/vsc/trac system?

I'd start with checking if there are any pending DTC codes, checking the battery cables and grounds, and inspecting the fuse box you found the burned EFI fuse in.

The only thing that I'm aware of that would cause the brakes to activate without the pedal is the VSC/Trac system if it sensed the car slipping. Perhaps you have a wheel speed sensor going bad and a separate issue rep grading the EFI fuse.

 

[Mike6158]

The under hood fuse box was / is dry. That's where the EFI fuse is. One side of the fuse was black from the top to about the point that the blade makes contact with the fuse holder.

The windshield was replaced in June. I've been through rain and car washes numerous times since. It's not leaking.

I'll check for codes in the morning. I finally found a hotel at 2am, got up at 7, and drove for 6 hours today. I've been traveling through Utah, Colorado, and New Mexico for the last two week. Other than the LC problems I've listed it's been a good but exhausting 2 weeks.

I am not sure where the wheel speed sensors are located or if mud and slush (snow) will affect them. I think the "lockup problem" was the VSC/Trac system and since an undercarriage wash at a car wash seemed to fix it maybe a wheel sensor was blocked? Or.. maybe a wheel sensor will kick off the cruise control

When the wheels locked... the LC swerved hard in each direction. If not for a good grip on the wheel there's no telling where I would have ended up. The road from Ouray to Durango doesn't leave much room for error.

PS- thanks for taking the time to reply

 

[TXLX100]

The brakes locking up outside of a slip situation isn't unheard of. Maybe this thread will give you some things to look for.

https://forum.ih8mud.com/threads/lx470-the-vsc-warning-light-goes-on.451272/

Hope you get it figured out.

 

[Mike6158]

Sounds like he found a solution. Kind of expensive and it doesn't explain why my problem went away (unless the cruise control issue is related)

They replaced the rack and pinion steering box, the tie rod ends and did a 4 wheel alinement with the promise that it would fix it for good.

It did..... no more problems with the vsc or brakes locking up....just the bank locking me out...... Jokes... The steering box, rod ends and alignment cost about $1100 for parts and $950 for labor. Yes that is painful but the lx 470 handles like new. And it's book value is about 12 to 15K, maybe more.IDK

The LC seems to wander compared to other vehicles I drive but I attributed it to being AWD. It's kind of like driving a marble down the road. Never tracks by itself. Maybe I've got rack and pinion issues??

 

[TXLX100]

It should track very straight, esp with a rack & pinion setup. My 98 LX requires little input going down the road (my ford truck is another story). You might have some alignment specs out or worn components.

 

[Mike6158]

I'll bet the rack and pinion is getting worn. I've got some time before my next long trip so I can fix it or have it fixed before then. I wonder if I should upgrade anything? I'm considering an air locker for the front (maybe rear too). Everything about the TLC seems pretty tough so it's hard to figure out when or if aftermarket is better than OEM.