Jeep 200 Cherokee, Service Manual

Page: 258 / 2119

Electric cooling fan 4.0L: With or without A/C
request the electric fan will come on only when the
coolant temperature is at least 106° C (223° F), and
will remain on until the coolant temperature drops to
103° C (217° F) or below. Regardless of coolant tem-
perature, When air conditioning system pressures
reach 2068.5
6
138 kPa (300
6
20 psi) the electric
fan will engage and continue to run until the A/C
system pressure drops to 1620.3 kPa (235 psi) mini-
mum, then the electric fan will shut off.
DIAGNOSIS AND TESTING
ON-BOARD DIAGNOSTICS (OBD)
COOLING SYSTEM RELATED DIAGNOSTICS
The Powertrain Control Module (PCM) has been
programmed to monitor the certain following cooling
system components:
•
If the engine has remained cool for too long a
period, such as with a stuck open thermostat, a Diag-
nostic Trouble Code (DTC) can be set.
•
If an open or shorted condition has developed in
the relay circuit controlling the electric radiator fan,
a Diagnostic Trouble Code (DTC) can be set.
If the problem is sensed in a monitored circuit
often enough to indicate an actual problem, a DTC is
stored. The DTC will be stored in the PCM memory
for eventual display to the service technician. (Refer
to Group 25, Emission Control Systems for proper
procedures)
ACCESSING DIAGNOSTIC TROUBLE CODES
To read DTC’s and to obtain cooling system data,
refer to Group 25, Emission Control Systems for
proper procedures.
DRB SCAN TOOL
For operation of the DRB scan tool, refer to the
appropriate Powertrain Diagnostic Procedures ser-
vice manual.
ACCESSORY DRIVE BELT DIAGNOSIS
VISUAL DIAGNOSIS
When diagnosing serpentine accessory drive belts,
small cracks that run across the ribbed surface of the
belt from rib to rib (Fig. 16), are considered normal.
These are not a reason to replace the belt. However,
cracks running along a rib (not across) are not nor-
mal. Any belt with cracks running along a rib must
be replaced (Fig. 16). Also replace the belt if it has
excessive wear, frayed cords or severe glazing.
Refer to the Accessory Drive Belt Diagnosis charts
for further belt diagnosis.
NOISE DIAGNOSIS
Noises generated by the accessory drive belt are
most noticeable at idle. Before replacing a belt to
resolve a noise condition, inspect all of the accessory
drive pulleys for alignment, glazing, or excessive end
play.
Fig. 15 Power Distribution Center (PDC)
1 – RIGHT FENDER
2 – BATTERY
3 – POWER DISTRIBUTION CENTER
Fig. 16 Belt Wear Patterns
1 – NORMAL CRACKS BELT OK
2 – NOT NORMAL CRACKS REPLACE BELT
XJ
COOLING SYSTEM 7 - 9
DESCRIPTION AND OPERATION (Continued)