On Sun, 21 Aug 2005 14:56:12 -0400, "shortmom" <fcshort
...@yahoo.com>
wrote:
>Recently the "BRAKE" and the "REAR ABS" warning lights came on and stayed
>on after brake inspection. Brake shoes are ok. Why is the light still
>on?
The BRAKE light can be turned on simply because the parking brake is
not fully released or the switch on it isn't going "off". Perhaps the
"inspection" messed up the switch or the guy didn't let the p brake
all the way off. I believe low brake fluid will also turn it on. If
none of those things is making the BRAKE light come on with the Rear
ABS light then note below that there seems to be only one trouble code
with should light both lights.
The two most common causes of the Rear ABS light coming on are a bad
speed sensor in the differential (near the top with wires going to it,
easy to replace yourself, costs about $20) and/or a bad RABS valve. In
my experience with two 92's the RABS valve can be bad but not set any
codes until you have to hit the brakes hard and make it "work". That
seems to make it get stuck or something and then the light comes on
and keeps coming back on. The RABS is on the drivers side frame rail,
on the inside of the rail near the fuel filter. It's a pain to remove
and replace. Price is about $150 for the part.
There is also a diagnostic connector you can use to read the codes
from the controller for the ABS system....
There are diagnostics (read: things that could turn on the light) on
five
system parts: (1)RABS (Rear Anti-lock Brake System) Isolate and Dump
Valve, (2) Ring gear speed sensor, (3) Master Cylinder fluid level,
(4)
Stoplamp switch circuit, and (5) the RABS control module. NOTE: The
Explorer/Ranger doesn't have a master cylinder pressure differential
switch; only the Aerostar has this.
Try and get the flashout code. For the Ranger/Explorer, this must be
obtained when the REAR ABS light is on (unlike the Aerostar, there is
no
memory). So you need to leave the truck running while you pull the
codes.
Locate the RABS Diagnostic connector. It is inside the cab,
under the dash just above the parking brake pedal where a 53-pin
wiring
connector goes through the firewall. It is a single orange/black wire
with an open connector on the end. Attach a jumper wire to the
connector,
and momentarily ground it. When the ground is made and broken, the
REAR
ABS light will give the flashout code. The code consists of a number
of
short flashes and ends with a long flash. The sum of the short
flashes
and the long flash is the code. The code will repeat until the key is
turned off.
RABS Flashout Codes
1 (should not occur)
2 Open Isolate circuit (In RABS Isolate/Dump valve)
3 Open dump circuit
4(w/ Red Brake Warn Light) RABS valve switch closed or open Dump
Valve
5 Rear brake (mechanical) problems or missing signal from 4X4
switch
6 Erratic or low ring gear speed sensor output
7 No Isolate Valve self-test
8 No Dump Valve self-test
9 Speed sensor resistance high
10 Speed sensor resistance low
11 Defective stoplamp switch circuit
12 Low brake fluid
13 RABS control module general failure
14 RABS module program check-sum error
15 RABS memory failure
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