ABS Code C0040?

[Mike534x]

Alright, I've been trying to solve this problem for the past week and a half and need some help. The Envoy suffers from the infamous "ABS shutter" when doing 5 MPH or less coming to a stop, hooking up the code reader revealed that it was the front right side speed sensor. I went in and took everything apart down to the hub to clean the mounting surface where the sensor resides, which did have a fair amount of rust building up. The tip of the magnet (?) on the sensor was slightly shaved away it looks like from hitting the inside so I replaced it with a new AC Delco sensor. I'm not sure what brand the after market sensor was, but the tip was a little different from the new one. Anyway, the surface is nice a smooth, applied some grease around the rubber boot of the sensor and installed and hooked everything back up. The ABS code disappeared, but the shutter is still present when braking. It is not nearly as bad, but it is a "little" bit better.

I do know the previous owner had both front wheel hub's replaced over the past few years, so I'm not sure if that plays a part in it. There are no ABS warning lights before/after replacing the sensor, and nothing is popping up as a pending code. Should I try replacing the right side wheel hub, or does it involve something with the wiring between the sensor and ABS module?

 

[littleblazer]

On both of the trucks the only cure was replacing the hub. Swapping sensors side to side changed nothing.

 

[Mike534x]

So its more then likely a hub issue? I wish I knew what brand the hub was, but whoever did the work did a shotty job putting on the new brake caliper, the bolts were only hand tight.

 

[littleblazer]

It may not be. You could try swapping them from side to side to see if it follows. Or you could test the circuit. I'd bet on the hub though especially if the new sensor didn't fix it. It's only happening on very slow gradual stops right? Just pedal pulsing but not full blown abs? More like it falls down right?

 

[Mike534x]

Yeah before replacing the sensor it felt exactly like that, now its just the pedal pulsing and the typical ABS sound when coming to a slow stop.

 

[Mooseman]

Yep. 90% of the time, the hub is at fault. Not sure of the reason. Could be the bearing running loose but not making noise yet. The fact your old sensor had rub marks kinda points that way. That or cheap hubs, which I have seen before.

 

[Mike534x]

I'm beginning to wonder if these were cheap hubs, too bad there is no way to tell unfortunately, and they're fairly rusted so who really knows. I ordered up a Timken hub off Amazon and will be installing it this weekend, so I'll post back if this corrects it or not.

 

[Mike534x]

Update:

Well we got the new hub installed and it still does it.

It feels a lot better, but it feels like the front driver side isn't catching well. Found yet another issue that popped up....when I test drove it, someone swerved in front of me and when slamming on the brakes there was a very unpleasant groan coming from the driver side rear. It looks like they put on cheapo non branded metallic pads on all four wheels.

Would cheap pads affect the ABS in any way? I ended up ordering a set of Monroe's all the way around to get that garbage out.

 

[Mooseman]

It shouldn't affect ABS. ABS normally activates when it detects wheel lockup during braking no matter the pad or road surface slipperiness.

Maybe it's the other one?

Very strange that they would put metallic pads as it came from the factory with ceramics. Would cause a lot of brake dust too.

 

[Mike534x]

Ahh alright that makes sense, figured I'd ask anyway. Its odd that there isn't a code tripping for the left side if that is that case, unless its small enough to not really set it off.

Yeah, not really sure why they threw metallic pads on here. They changed the rotors and calipers all the way around, so you figure they would of bothered putting the right pads in.

 

[littleblazer]

Since you bought a new sensor why not try it on the drivers side? Also the back of the hub by the bearing should have manufacturer info. The bearing itself that is.

 

[Mooseman]

This particular problem never throws a code or light, otherwise ABS wouldn't work at all.

 

[Mike534x]

Really? I'm gonna try pulling the tire tomorrow and swap sensors to see what happens.

Since you bought a new sensor why not try it on the drivers side? Also the back of the hub by the bearing should have manufacturer info. The bearing itself that is.

I did look at the back of the bearing but couldn't see anything like the manufacturers info, there is a decent amount of rust though so it definitely wasn't replaced recently.

 

[Mike534x]

Problem is solved!

With the weather being decent enough to work outside again, I pulled the driver side apart and the sensor broke off inside the assembly after getting it free. It was pretty rusted through, and looked like it may have probably been the original hub. I went over to Advanced and got a hub made by Moog, the 20% off coupon brought it down to what the Timken costs on Rockauto/Amazon. While in there I swapped the front and rear brake pads out for the Monroe Ceramics I ordered and the ABS pulsation is completely gone and it stops on a dime too!