Mazda MX-6 1998, Workshop Manual

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TROUBLESHOOTING [ENGINE CONTROL KL]
17 COOLING SYSTEM CONCERNS OVERHEATING
DESCRIPTION Engine runs at higher than normal temperature/Overheats
POSSIBLE
CAUSE
• Improper coolant level
• Coolant leaks
• Improper water/anti-freeze mixture
• Poor radiator condition
• Radiator hoses damage
• Improper or damaged radiator cap
• Malfunction of coolant overflow system parts
• Drive belt damage
• Blown fuses
• Excessive pressure of A/C system
• Fans reverse rotation
• Thermostat malfunction
• Condenser fan inoperative
• Main cooling fan inoperative
• Improper tension of drive belt
STEP INSPECTION ACTION
1 Check following:
• Engine coolant level.
• Coolant leaks.
• Water and anti-freeze mixture.
• Radiator condition.
• Collapsed or restricted radiator hoses.
• Radiator pressure cap.
• Overflow system.
• Fan rotational direction.
• Fuses.
Are all items okay?
Yes Go to next step.
No Service as necessary.
Repeat step 1.
2
Cool down engine.
Turned A/C switch OFF.
Connect NGS tester to DLC.
Access ECT V PID.
Start engine and record ECT voltage reading
every 60 seconds.
Note
• When ECT voltage reverses direction trend
or changes slightly (0.03 volt or less),
thermostat has opened.
Is thermostat opening voltage okay?
Thermostat opening voltage
Approx. 0.6— 0.9 V
Yes Engine coolant temperature and thermostat are okay.
Go to next step.
No Remove thermostat from engine and verify operation.
If temperature gauge on instrument cluster indicates
normal operation but ECT V is not same as temperature
gauge reading, check engine coolant temperature sensor.
If temperature gauge on instrument cluster indicated
overheating but ECT V is normal, check temperature
gauge and heat gauge unit.
3 Retrieve and record any continuous memory,
KOEO and KOER DTCs.
Are there any DTCs displayed?
Yes
Go to appropriate DTC test.
No Go to next step.
4 Start engine and run it at idle.
Turn A/C switch on.
Does A/C compressor engage?
Yes Go to step 6.
No
Check following and repair or replace as necessary:
• Refrigerant charging amount.
• Open circuit between A/C magnet clutch and PCM.
• Seized A/C magnet clutch.
• A/C magnet clutch malfunction.
If all items are okay, go to next step.
5 Connect NGS tester to DLC.
Access ACCS PID on NGS tester.
Start engine and run it at idle.
Turn A/C switch on.
Does ACCS PID indicate ON?
Yes
Go to next step.
No Check follows:
• A/C pressure switch(es) operation.
• A/C switch stuck open.
• Open or short circuit between A/C pressure switch and
PCM.
01-01B-159