Actron GM Code Scanner CP9001 - Manual (Page 47)

47
ABS TIPS
Useful Hints to Know When
Troubleshooting ABS Systems
IMPORTANT: Always follow vehicle service manual procedures for any ABS
repairs. (Manual listings on page 4.)
• Do a thorough visual and “hands-on”
inspection first. You can often find the
cause of many problems by just
looking.
• ABS systems rely on accurate wheel
sensor signals. Anything which
interferes with the wheel sensor can
create intermittent problems or set
trouble codes. Note the following:
–Do not mix tire sizes. Rolling
diameter must be the same for all
four tires. Differently sized tires (or
using a “compact” spare) can cause
inaccurate wheel speed sensor
operation.
–Do not tap the speed sensor or
toothed sensor ring. Tapping these
parts can disturb their magnetic
properties and upset wheel speed
sensor operation. Press (do not
hammer) toothed sensor ring onto
hub, if service is required.
–Do not overtighten wheel lug nuts.
(Specifications are in vehicle
service manual.) Brake drum or
rotor may bend causing inaccurate
wheel speed sensor operation.
–Do not coat wheel speed sensor
parts with grease. Refer to vehicle
service manual for recommended
material.
–Check spacing between wheel
speed sensor and toothed ring,
especially after servicing. Incorrect
spacing can cause faulty sensor
operation. Specifications are in
vehicle service manual.
–Check for cracked or missing teeth
on the wheel speed sensor ring.
• Spinning tires (or axle) on a
stationary vehicle during a service
procedure may set ABS trouble
codes.
• Radio transmitters can interfere with
operation of ABS computer. Keep
antenna wiring from a CB radio or
portable telephone away from ABS
wiring
• Check ABS power circuits:
–Make sure vehicle alternator and
voltage regulator are working
properly.
–Make sure vehicle battery is fully
charged.
–Make sure all ABS fuses, fusible
links and relays are good
• Inspect wiring for:
–Contact
with sharp
edges.
(This
happens
often.)
–Contact
with hot surfaces, such as exhaust
manifolds.
–Pinched, burned or chafed
insulation.
–Proper routing and connections.
• Check electrical connectors for:
–Corrosion on pins.
–Bent or damaged pins.
–Contacts not properly seated in
housing.
–Bad wire crimps to terminals.
Problems with electrical
connectors are common.
Inspect carefully. Note that some
connectors use a special grease on
the contacts to prevent corrosion. Do
not wipe off! Obtain extra grease, if