A few teeth on this WSS exciter ring are not clean and are damaged. This led to false activation.
What sets modern antilock braking systems (ABS) apart from conventional, hydraulic brakes is their electronic controls. Often,
barely-measurable amounts of current can make the difference between full antilock brake systems (ABS) functionality and a
tough-to-diagnose problem. Here are some tips — some general, some specific — that are worth remembering when servicing ABS
electronics.
See the light
However, the teeth on the WSS exciter ring are clean and undamaged.
Stop lamps aren't just for letting following drivers know a vehicle is decelerating. In some ABS control schemes, the microprocessor
finds out there's a "brake apply request" by detecting a voltage drop as current begins running through those lights. But
voltage won't drop in an incomplete circuit — like when bulbs are burned out. Some systems set up this way monitor voltage
drop to the stoplights in the taillights; others work with the center high-mount stop lamp (CHMSL). Some use them all. In
any event, make sure all glow.
There's a related scenario when a seemingly brake-unrelated vehicle modification can cause antilock brake glitches: adding
a rear spoiler with an additional third brakelight. It could cause voltage drop to vary beyond what the ABS computer is looking
for. (As if that weren't enough, federal regulations frown on having redundant CHMSLs — even though you see cars with an extra
third brakelight every day.) You and the customer may have to decide which light to disconnect, especially if the extra current
load causes the ABS to malfunction.
A professionally performed solder splice is the best way to repair a wire. Shrink tubing with internal sealant will insulate
the connection.
Speaking of lights, the telltale lamps on the instrument panel do more than let the motorist know their foundation or antilock
brakes need service. How and when they glow can help you troubleshoot malfunctions.
Hard or soft?
Some manufacturers once called for the entire underhood harness to be replaced if the lead heading to a WSS was damaged. Today
many allow splices if properly executed.
A hard code indicates a present condition and will remain (or recur) even if you clear it, unless you fix its underlying cause.
A soft code indicates a problem that may have existed before, but isn't there currently. However, clearing a soft code doesn't
necessarily mean you'll never see it again. If the condition it represents is intermittent, the code will come back when the
condition comes back.
Ford wrapped the harnesses on some Crown Victorias so tightly (Ford conduit) that any trapped moisture couldn't escape.
Once you've repaired a condition represented by a diagnostic trouble code (DTC) and cleared the code from memory, interrogate
the system at least once more. Here are two good reasons why. First, you'll verify that the code is gone; and also, because
some systems are capable of displaying only a limited number of codes at once, you may see one or more additional DTCs that
weren't evident previously. They're not new, they just didn't become accessible until codes further up the conga line were
displayed, their causes fixed, then cleared.
Paul Zangari is a freelance writer specializing in technical autmotive subjects. He also is the host of a weekly radio show airing in Providence, R.I., called "Drive-Thru Radio" on station WPRO-AM.
Articles by Paul Zangari
