So last year after a few weeks on jack stands, headers and some new axle joints I failed to put back on my front dust shields while installing my hubs. Finally got around putting them back on today.

In a bone head move I forgot to plug in the sensor on the frame rail on the driver side. To add to the confusion, I also ran the battery down, lot of wheel turning with key on - to get to those hub bolts. So get all done have to jump the truck, it starts up and I got an ABS light on - jump out and plug in the drivers side sensor.

Drive about 5 miles and then stop to get gas, no issues up until this point, truck feels great. While filling the tank I clear the ABS code, restart the truck YEAH ABS code is gone. Leave gas station and first stop I get a really big ABS pulse in the pedal and a huge yank of the wheel to the drivers side when coming to a stop. ABS light still off.

Drive 5 more miles and this repeats at every stop, come home. Check both sensors again, both plugged in and are tight. Unhook battery cables let it sit for awhile, hook them back up and off for another drive.

Same nasty pulse when stopping, only at the very end of the stop with a very hard pull to the driver's side. Same as before. Stop at a drive thru, while I'm sitting and waiting, my ABS lights back up. Not moving just sitting and idling, get my food pull out and now my truck is back to driving fine. No pulsing no pulling.

WTF??? ABS light on truck drives great, light off ABS is possessed. Now we know my truck is harboring an evil demon regardless, but WTF...any ideas?

 

That abs stuff is pretty technical and elaborate (are those the right words?), it's not like 40 years ago when it was all straightforward. I have replaced almost everything in my computers but when they have a glitch I usually cross my fingers and hope it corrects itself. Maybe pray to the abs gods ?

If it happened right after installing the deflectors, take a close look around there for any loose, cracked, or broken connections.

 

What code are you getting ? You have checked your connections , I am sure ...

 

I have checked all the connections, unplugged, replugged....confession on the code....I didn't read it. I knew why I got a code, I started the truck with the drivers side sensor hanging off the frame rail. So I plugged in the scanner and went straight to "clear codes" - I didn't even check the actual code - I mean I KNOW (or thought I knew) what it was - since I left a sensor unplugged.

But now that the ABS light is back on - I thought I can go scan it now and get the code. Hook up the SCT and it's reading No Codes. But by god the ABS light is on, and with the ABS light on the truck runs perfect. I'm afraid to have it go off again, because when it goes off - the truck goes nutz with the pulsing and pulling to the left.

But bottom line, ABS light is on, I currently have no codes and truck isn't pulling.....I will clear the code in the morning and see what happens. My prediction is the pulsing and pulling returns.

Guuuhhhhrrrr - that make no sense, but it is the reality.

 

ABS light on and no codes ? Do I read that correctly ? Sounds like a communication issue with your scan tool . Anyhow , If the light is off , and the ABS engages at low speed , that sounds like a sensor , tone ring , or wiring issue . Proper communication and Live data would be useful , A proper pin out and a lab scope would be better ! Best of luck !

 

I am a general mechanic with no X experience but I can fix anything. I would take the "Bundle Route"..

Disconnect Battery
Disconnect Sensors
Disconnect ECU/PCM

Get up in the morning and reconnect.


I know it sounds strange but it works for a 26 million dollar Apache, it can work for anything. Oh and I work on cars too.

 

I believe you need an ABS scanner to read ABS codes, don't think they come up with a standard OBD reader.

Leaving things unplugged for a while sounds like a reasonable next step. I've seen it work on other vehicles too. If that doesn't work, a new sensor would be my next try. Any chance it got bumped or damaged somehow during the work?

 

Which one? Aren't they a little pricey?

 

You read that right,
ABS warning light on = drives normal.
ABS warning light off = pulsing pulling drivers side.

Check - battery sensors been unplugged all night - should I pull the ECU fuse before I put it all back?

Well I didn't drop it or anything but it's ways possible.

When the truck does this buzz/pedal pulse the truck pulls really hard to the left. Normal brake logic would mean I had a stuck something on passenger side causing the brake to fail at engaging. But I just don't "get" ABS and am not sure if my logic is sound. Gut tells me it's the drivers side causing the issue, it's the sensor I forgot to plug in, it sure sounds and feels drivers side, but if that sensor was faulty and the ABS was kicking in on the drivers side only; "when it shouldn't" wouldn't that reduce the braking power to the drivers side and cause it to pull to the right? In a normal circumstance if one of your front wheels senses an issue that engages ABS - do both automatically engage?

By the way, no ABS should be kicking it at all, I'm driving no more than 40mph, and on completely dry pavement, and stopping normally.

 

When the ABS light is "ON", that means the ABS system is off-line and you have only standard hydraulic braking. Then the ABS light is "OFF" during normal driving, the system is in standby and is monitoring the sensors for an abnormal braking event that will call for ABS-assisted braking.

Therefore, it is completely normal for you to have normal braking when the light is on provided there are no hydraulic concerns.

 

^^^ This.

I went through something similar with my Lincoln when I replaced the front wheel bearings. No ABS light, but the system went NUTS when I touched the brake pedal. Scanned it with AE and found no trouble codes.

I restarted AE and had it connect to the ABS system. With the car in the shop with the wheels in the air I had it display wheel speeds on a graph. Spin the passenger side wheel as fast as I could and let it come to a stop, do the same for the driver's side, and then I looked at the graphs. Passenger side looked smooth and linear, but the driver's side was spiking to 0 about once per second. This narrowed it down to the driver's side sensor. Turned out to be a bad wheel bearing with the tone ring pressed on too far for the sensor to read.

I disagree with Brent in the respect that the system is complex; it really isn't. But without something like AutoEnginuity or another capable scan tool you have no way of understanding what the ABS system is seeing and doing. I'd triple check all of your connections and play close attention to the passenger side if it's pulling to the left. Logic dictates that the system is seeing a bad signal from the passenger side and cutting brake pressure to that wheel.

 

ABS is a simple system with a complex valving system at the ABS module. You will need a scanner that reads ABS codes. Go to the local box parts store and ask them to read the codes. Advance is the only one near me that has the scanner for it.

Good luck with the DEMON truck!

You might want to get a Catholic Priest to do an exorcism on it!

 

Tom and project have this right. Look to the passenger sensor if you can't test with AE.

 

Thanks and AMEN!

 

That dust shield should have that tab over the abs sensor wire, from the pic, it looks to me like the tab is jammed into the abs sensor.