RE: Need ABS and check engine help!!!

From: Ronald Wong (ron-wong@cox.net)
Date: Fri Aug 02 2002 - 20:23:22 EDT


Slightly different for ABS measurement but you're absolutely right for the
front wheels. In RWABS the front wheel speed sensors send information to
the CABS which forwards it on to the PCM. That information is also used for
RWABS. When you have 4-wheel ABS you have an additional CABS for the front
wheels but the rotations are still matched from the front to the rear.

Ron
00 PB SLT QC 4X2 5.9 46RE 3.92 LSD
For modifications see my DML Profile (URL follows)
http://www.twistedbits.net/WWWProfile/dakota/Kw9pV1EkFeOYY

-----Original Message-----
From: owner-dakota-truck@dakota-truck.net
[mailto:owner-dakota-truck@dakota-truck.net]On Behalf Of Vic
Sent: Friday, August 02, 2002 7:51 AM
To: dakota-truck@dakota-truck.net
Subject: Re: DML: Need ABS and check engine help!!!

Except for the fact that the rear tire rotation is being measured by axle
rotation which estimates the tire rotation by the PCM knowing what size your
tires are, while the fronts actually measure the tire rotation.

So if your PCM thinks you have 31"s (Original Equipment for my Dakota) the
PCM will calculate rear wheel speed by calculating how fast a 31" tire will
rotate given the axle rotation speed. If you really had 33"s, the
calculated wheel speed would be slower than the actual wheel speed. At the
same time the fronts will be accurately measured.

This is the case for 4-wheel ABS. I think rear ABS only is different.
>
> Wouldn't the above situation only cause a code if someone were to
> change the diameter of the rears without also changing the fronts?
> Seems like if someone was just getting bigger wheels, for example
> going from 31s to 33s, they generally change out all 4, and as far
> as the computer is concerned, it just looks like the person started
> driving around at 52mph all the time instead of 55...
>
>
>
> --
>
> -Jon-
>
> .---- Jon Steiger ------ jon@dakota-truck.net or
jon@jonsteiger.com -----.
> | I'm the: AOPA, DoD, EAA, NMA, NRA, SPA, USUA. Rec & UL Pilot - SEL
|
> | '70 Barracuda, '92 Ram 4x4, '96 Dakota, '96 Intruder 1400, '96 FireFly
|
> `-----------------------------------------
http://www.jonsteiger.com ----'
>



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