1. Engine Cooling System
Trouble Possible cause Corrective action
Over-heatinga. Insufficient engine coolantReplenish engine coolant, inspect for leakage, and
repair.
b. Loose timing belt Repair or replace timing belt tensioner.
c. Oil on drive belt Replace.
d. Malfunction of thermostat Replace.
e. Malfunction of engine coolant pump Replace.
f. Clogged engine coolant passage Clean.
g. Improper ignition timingInspect and repair ignition control system.
h. Clogged or leaking radiator Clean or repair, or replace.
i. Improper engine oil in engine coolant Replace engine coolant.
j. Air/fuel mixture ratio too leanInspect and repair fuel injection system.
k. Excessive back pressure in exhaust system Clean or replace.
l. Insufficient clearance between piston and cylinder Adjust or replace.
m. Slipping clutch Repair or replace.
n. Dragging brake Adjust.
o. Improper transmission oil Replace.
p. Defective thermostat Replace.
q. Malfunction of electric fanInspect radiator fan relay, engine coolant temperature
sensor or radiator motor and replace there.
Over-coolinga. Atmospheric temperature extremely low Partly cover radiator front area.
b. Defective thermostat Replace.
Engine coolant
leaks.a. Loosened or damaged connecting units on hoses Repair or replace.
b. Leakage from engine coolant pump Replace.
c. Leakage from engine coolant pipe Repair or replace.
d. Leakage around cylinder head gasket Retighten cylinder head bolts or replace gasket.
e. Damaged or cracked cylinder head and crankcase Repair or replace.
f. Damaged or cracked thermostat case Repair or replace.
g. Leakage from radiator Repair or replace.
Noisea. Defective drive belt Replace.
b. Defective radiator fan Replace.
c. Defective engine coolant pump bearing Replace engine coolant pump.
d. Defective engine coolant pump mechanical seal Replace engine coolant pump.
19
2-5DIAGNOSTICS
1. Engine Cooling System
OBD0527
BI: DTC P1500
—RADIATOR FAN RELAY 1 CIRCUIT
MALFUNCTION (FAN
—1)—
DESCRIPTION:
The engine cooling system consists of a down-flow
radiator which features high heat-dissipation performance,
an electric motor fan, an engine coolant pump, a
thermostat, and an engine coolant temperature sensor.
The ON-OFF control of the radiator fan is governed by
the ECM which receives signals sent from the engine cool-
ant temperature sensor. On models which are equipped
with an air conditioning system, the ECM receives signals
sent from the engine coolant temperature sensor, vehicle
speed sensor 2 and A/C switch. These signals simulta-
neously turn ON or OFF the radiator main fan and radiator
sub fan as well as setting them at“HI”or“LO”speed.
[Without A/C models]
Engine coolant temperature signal *1ECM output signal Operation of radiator fan
Radiator fan relay 1 Main
ON ON ON
OFF OFF OFF
*1 ON: Above 95°C (203°F), OFF: Below 89°C (192°F)
[With A/C models]
Engine coolant
temperature
signal *2A/C compressorVehicle speed
signal *3ECM output signal Operation of radiator fan
Radiator fan
relay 1Radiator fan
relay 2Main Sub
ONONON ON ON HI HI
OFF ON ON HI HI
OFFON ON ON HI HI
OFF ON OFF LO LO
OFFONON ON ON HI HI
OFF ON OFF LO LO
OFFON OFF OFF OFF OFF
OFF OFF OFF OFF OFF
*2 ON: Above 95°C (203°F), OFF: Below 89°C (192°F)
*3 ON: Above 20 km/h (12 MPH), OFF: Below 10 km/h (6 MPH)
331
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code
