ABS Light

I drive a 1998 dodge stratus. Good, reliable car, but I have noticed
this few weeks that the ABS suddenly turns on. When I reach my
destination, I turn on the car and the ABS light is no longer on.
However, when I am driving it turns on again. Any suggestions how to
fix this problem? how do I make sure my ABS is working? Thanks.

 

By "the ABS suddenly turns on" I assume you mean the ABS light.

The first step for a mechanic would be to check for stored trouble
codes. If the light came on while driving you *should* have a code in
memory. That is the easiest way to go forward with diagnosis. Once
you have your car repaired, you can test/verify ABS operation by
braking hard on a wet surface and feeling for the telltale
shaking/vibration that accompanies ABS operation. Obviously the car
should come to a rather abrupt halt as well; shaking without actually
stopping is a sign that the ABS system is not working also. Do this
test in a large unoccupied parking lot at speeds < 10mph for safety.

Toyota MDT in MO

 

OK, what's happening is when you turn on the car the ABS system
runs it's self-check and finds nothing wrong. Then, when you start
to move, the ABS knows your moving (the body module tells it this)
but it's also noticing no sense pulses from one of your wheel sensors.

Since if your moving you obviously are going to have sense pulses
from the wheel sensors, the ABS system correctly concludes you
have a bad sensor, it then turns on the ABS warning light, and shuts
the system down

ABS will not work when the light is on.

You need a scan tool to find out which wheel sensor is bad.

You can get a replacement sensor from the dealer for about $150.
They are actually not that difficult to replace in your driveway, but
unless you know exactly which sensor is bad, shotgunning is going to
rapidly waste money.

Sometimes what happens is something gets kicked up from the road
and damages a sensor, or wiring to the sensor and you can make a
visual check and see it.

Ted

 

Actually, with the vehicle schematics, find the connector that plugs
into the ABS controller and the two pins for each sensor - I just did
this on a Ford car of mine - same setup. Unplug the controller
connector and ohm across each sensor thru the connector pins. 'Good'
should be in the 1200 ohm range. If/when you find the one that reads
open (or shorted), you might rule out that the cabling is open/shorted
by demating and ohming out any intermediate connectors going to the
sensor - but most likely - as Ted says - it's the sensor itself.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

This is one area you really really want to have the computer tell you
where the complaint is. The connectors are usually buried and if it's
an open sensor and the open is due to corrosion or a bad contact in
the connector itself - your ohming test will find nothing wrong, you will
put everything back together, it will work for a week or a month then
die again. And, changing the sensor itself is a royal PIA, unless that is
you enjoy lying under the car while showers of dirt and dust knocked
off the bodywork fall down on your face while you reach up to manipulate
stuff. You really don't want to make a mistake and change out a
good sensor.

Ted

 

True for the scenarios you describe. In my case the sensor itself was
bad - had actually been damaged on the tip, and it was solid open
circuit. I wouldn't *not* do the ohmmeter test just because certain
problems may not be detected - that's a risk of any troubleshooting
procedure - including using a code reader. What you describe is true
with many intermittent type problems. On the other hand, if the problem
is corroded terminals in the connector, then getting in the habit of
properly cleaning and lubricating with silicone grease made for
eletrical connectors after you do the (possibly unsuccessful) ohm test
will likely fix the problem


And, changing the sensor itself is a royal PIA, unless that is

The hardships you describe are generally true of working on cars, and
not specific to ABS sensors. IOW - if that keeps you from working on
the sensor, then you aren't a DIY'er anyway - take it to a shop or
dealer and leave money as you would with any problem or service - and
also possibly end up with the problem stil there - there are no
guarantees either way.

The ohm test will absolutely not tell you that a good sensor is bad - so
replacing a perfectly good sensor is not an issue.

I don't think it's more of a PITA than anything else that you do on cars
today. On the Ford I just did, it was actually not too difficult -
worst part was peeling away the fender liner to get to the connector of
the sensor cable to replace it once I had determeined that it was
definitely bad with the ohmmeter used on the main connector back at the
ABS controller and then on the intermediate connector.

On some cars it takes a special scan tool to read the ABS stuff - such
was the case with my Ford. When faced with paying the dealer their
minimum 1 hr. labor charge to hook their machine up for 5 minutes vs. my
possibly finding the problem for $0 and 10 minutes of time, it was a no
brainer - and I'm usually good at no brainers (even though I can mess
them up too). ")

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')