Safari Van M V6-262 4.3L VIN Z TBI (1990)
Hydraulic Control Assembly - Antilock Brakes: Customer Interest
ABS - Intermittent Loss of Power or Ground, Codes Set
GMC NUMBER:
90-5E-86
GROUP:
5E Anti-Lock Brakes
DATE:
August, 1990
CORPORATE
NUMBER:
065014
SUBJECT:
LOSS OF POWER OR GROUND - 4WAL DIAGNOSIS INFORMATION
MODELS:
1990 M/L VANS WITH FOUR WHEEL ANTI-LOCK BRAKES
An intermittent loss of power or ground to the the 4WAL Electro Hydraulic Control Unit (EHCU) may cause a variety of symptoms and can be very
difficult to diagnose. Whenever diagnosing a 4WAL complaint technicians should first ensure that the system is well grounded and has a stable power
connection. The following code sequences are common indicators of intermittent power or ground conditions.
LOSS OF TWO PIN GROUND:
4WAL
73, 86
CODES
or 73, 86, 66
or 47, 66, 68, 48, 43, 44, 53, 54, 86 or any combination of the above codes
LOSS OF POWER:
4WAL CODE 65
Other indications of possible intermittent losses of power or ground would include.
-
Difficulty in resetting the codes
-
Other vehicle electrical abnormalities, particularly the A/C and Blower Motor which share the same power connection with the 4WAL
system.
^Evidence or knowledge of prior electrical repairs which might affect 4WAL system power/ground.
When a technician suspects that a vehicle may be intermittently losing either power or ground to the 4WAL system, both ten pin and two pin connections
to the unit should be inspected and cleaned with a wire brush of all corrosion. Following this, an appropriately sized star washer should be installed at
each source connection to ensure a secure reliable connection. The 4WAL power connection is located just below the bulkhead connector of the vehicle
while the ground is located on a stud at the radiator support. Technicians should take note that power to the EHCU through the 10 pin connector is
provided through the "brake" fuse.
Once the power/ground sources have been verified as good, technicians should clear the codes set and run three (3) function tests with Tech One to
verify the repair.
