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7-8
COOLING SYSTEM
DIAGNOSIS AND TESTING (Continued)
may indicate the result of a failure, but never iden-
tify the failed component directly.
It is possible that a DTC for a monitored circuit
may not be entered into memory even though a mal-
function has occurred . Refer to On-Board Diagnostics
(OBD) in Group 14, Fuel Systems for additional DTC
information .
ACCESSING DIAGNOSTIC TROUBLE CODES
A stored Diagnostic Trouble. Code (DTC) can be dis-
played by cycling the ignition key On-Off-On-Off-On
within three seconds and observing the malfunction
indicator lamp . This lamp is displayed on the instru-
ment panel as the CHECK ENGINE lamp.
They can also be displayed through the use of the
Diagnostic Readout Box (DRB) scan tool . The DRB
connects to the data link connector located under the
instrument panel left of the steering column (Fig.
12) . For operation of the DRB, refer to the appropri-
ate Powertrain Diagnostic Procedures service man-
ual .
16-WAY
DATA LINK
CONNECTOR
BOTTOM
OF INSTRUMENT
PANEL
Fig. 12 16-Way Data Link Connector-Typical
EXAMPLES:
" If the lamp flashes 1 time, pauses and flashes 2
more times, a flashing Diagnostic Trouble Code
(DTC) number 12 is indicated . If this code is
observed, it is indicating that the battery has been
disconnected within the last 50 key-on cycles . It
could also indicate that battery voltage has been dis-
connected to the PCM . In either case, other DTC's
may have been erased.
" If the lamp flashes 1 time, pauses and flashes 7
more times, a flashing Diagnostic Trouble Code
(DTC) number 17 is indicated .
TJ
" If the lamp flashes 3 times, pauses and flashes 5
more times, a flashing Diagnostic Trouble Code
(DTC) number 35 is indicated .
After
any stored DTC information has been
observed, the display will end with a flashing DTC
number 55 . This will indicate the end of all stored
information .
ERASING TROUBLE CODES
After the problem has been repaired, the DRB scan
tool must be used to erase a DTC . Refer to the appro-
priate
Powertrain Diagnostic
Procedures
service
manual for operation of the DRB scan tool .
DRB SCAN TOOL
For operation of the DRB scan tool, refer to the
appropriate Powertrain Diagnostic Procedures ser-
vice manual .
WATER PUMP
LOOSE IMPELLER
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse .
WARNING :
DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE . SERIOUS BURNS FROM THE COOL-
ANT CAN OCCUR.
(1) Drain the cooling system .
(2) Loosen the fan belt .
(3) Disconnect the lower radiator hose from the
water pump .
(4) Bend a stiff clothes hanger or welding rod as
shown in (Fig . 13) .
(5) Position the rod in the water pump inlet and
attempt to hold the impeller while turning the fan
blades. If equipped with a viscous fan drive, turn the
water pump shaft with a breaker bar and socket
attached to a mounting flange nut . If the impeller is
loose and can be held with the rod while the fan
blades are turning, the pump is defective . If the
impeller turns, the pump is OK.
(6) Connect the hose and install the coolant, or
proceed with repairs .
WATER PUMP TEST
A quick test to determine if the pump is working is
to check if the heater warms properly . A defective
water pump will not be able to circulate heated cool-
ant through the long heater hose to the heater core .
ACCESSORY DRIVE BELT
When diagnosing serpentine accessory drive belts,
small cracks that run across the ribbed surface of the
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Troubleshooting
