Mazda 6. Manual - part 173

F–214

TROUBLESHOOTING 

End Of Sie

NO.16 HIGH OIL CONSUMPTION/LEAKAGE

A6E398018881W18

Diagnostic procedure

End Of Sie

5

Is strong blue spark visible at each disconnected 
high-tension lead while cranking engine?

Yes

Inspect for following:

• Spark plugs malfunction

• Improperly installed CMP sensor

• Damage of trigger wheel on camshaft

• Open or short circuit on CMP sensor

• Open or short circuit between CMP sensor and 

PCM terminal 2J or 2M

Repair or replace malfunctioning parts.
If okay, go to next step.

No

Inspect following:

• High-tension leads

• Ignition coil and connector

6

Install fuel pressure gauge between fuel pipe 
and fuel distributor.
Start engine and run it at idle.
Measure fuel line pressure at idle.
Is fuel line pressure correct at idle?
(See 

F–20 FUEL LINE PRESSURE 

INSPECTION

)

Yes

Go to next step.

No

Zero or low:
Inspect for clogged fuel line.
If okay, replace fuel pump unit.
High:
Replace fuel pump unit.

7

Remove and shake PCV valve.
Does PCV valve rattle?

Yes

Go to next step.

No

Replace PCV valve.

8

Inspect for fuel saturation inside charcoal 
canister.
Is excess amount of liquid fuel present in 
canister?

Yes

Replace charcoal canister.

No

Inspect fuel tank vent system.
Then, go to next step.

9

Is there restriction in exhaust system?

Yes

Inspect exhaust system.

No

Inspect EGR system.
(See 

F–233 EGR Control System Inspection

.)

10

Inspect threeway catalytic converter.
(See 

F–41 THREE-WAY CATALYTIC 

CONVERTER (TWC) INSPECTION

.)

Is threeway catalytic converter okay?

Yes

Inspect EGR system.
(See 

F–233 EGR Control System Inspection

.)

No

Replace threeway catalytic converter.

11

Verify test results.

• If okay, return to diagnostic index to service any additional symptoms.

• If malfunction remains, replace PCM.

STEP

INSPECTION

RESULTS

ACTION

16

HIGH OIL CONSUMPTION/LEAKAGE

DESCRIPTION

Oil consumption is excessive.

POSSIBLE CAUSE

• PCV valve malfunction

• Improper dipstick

• Improper engine oil viscosity

• Engine internal parts malfunction

STEP

INSPECTION

RESULTS

ACTION

1

Remove and shake PCV valve.
Does PCV valve rattle?

Yes

Go to next step.

No

Replace PCV valve.

2

Inspect for following:

• External leakage

• Proper dipstick

• Proper engine oil viscosity

Are all items okay?

Yes

Inspect internal engine parts such as valves, valve 
guides, valve stem seals, cylinder head drain passage, 
and piston rings.

No

Service as necessary.
Repeat Step 2.

3

Verify test results.

• If okay, return to diagnostic index to service any additional symptoms.

• If malfunction remains, replace PCM.

TROUBLESHOOTING 

F–215

F

NO.17 COOLING SYSTEM CONCERNS-OVERHEATING

A6E398018881W19

Diagnostic procedure

17

COOLING SYSTEM CONCERNS     -OVERHEATING

DESCRIPTION

Engine runs at higher than normal temperature/overheats.

POSSIBLE CAUSE

• Improper coolant level

• Blown fuses

• Coolant leakage

• Excessive A/C system pressure

• A/C system operation is improper

• Improper water/anti-freeze mixture

• Fans reverse rotation

• Poor radiator condition

• Thermostat malfunction

• Radiator hoses damage

• Condenser fan is inoperative.

• Improper or damaged radiator cap

• Cooling fan is inoperative.

• Coolant overflow system malfunction

• Improper tension of drive belt

• Drive belt damage

STEP

INSPECTION

RESULTS

ACTION

1

Inspect following:

• Engine coolant level

• Coolant leakage

• 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

Connect WDS or equivalent to DLC-2.
Retrieve any continuous memory, KOEO and 
KOER DTCs.
Are there any DTCs displayed?

Yes

DTC is displayed:
Go to appropriate DTC test.

No

No DTC is displayed:
Go to next step.

3

Start engine and run it at idle speed.
Turn A/C switch on.
Does A/C compressor engage?

Yes

Go to Step 5.

No

Inspect for following and repair or replace as 
necessary:

• Refrigerant charging amount

• Open circuit between A/C relay and PCM terminal 

4O

• Seized A/C magnetic clutch

• A/C magnetic clutch malfunction

If all items are okay, go to next step.

4

Connect WDS or equivalent to DLC-2.
Access ACSW PID.
Start engine and run it at idle speed.
Turn A/C switch on.
Does ACSW PID read ON?

Yes

Go to next step.

No

Inspect following:

• Refrigerant pressure switch operation

• A/C switch is stuck open.

• Open or short circuit between refrigerant pressure 

switch and PCM terminal 1AC

• Open circuit of blower motor fan switch and resistor 

(if blower motor does not operate)

• Evaporator temperature sensor and A/C amplifier

5

Inspect cooling fan control system operation.
(See 

F–234 Cooling Fan Control System 

Inspection

.)

Does cooling fan control system work properly?

Yes

Go to next step.

No

Repair or replace malfunctioning parts.

6

Is drive belt okay?

Yes

Go to next step.

No

Replace drive belt.

7

Is there any leakage around heater unit in 
passenger compartment?

Yes

Inspect and service heater for leakage.

No

Go to next step.

8

Is there any leakage at coolant hoses and/or 
radiator?

Yes

Replace malfunctioning part.

No

Go to next step.

F–216

TROUBLESHOOTING 

End Of Sie

NO.18 COOLING SYSTEM CONCERNS-RUNS COLD

A6E398018881W20

Diagnostic procedure

End Of Sie

9

Cool down the engine.
Remove thermostat and inspect operation.
(See 

E–7 THERMOSTAT REMOVAL/

INSTALLATION

.)

(See 

E–8 THERMOSTAT INSPECTION

.)

Is thermostat okay?

Yes

Engine coolant temperature and thermostat are okay,
inspect engine block for leakage or blockage.

No

Access ECT PID.
Inspect for both ECT PID and temperature gauge 
readings.
If temperature gauge on instrument cluster indicates 
normal range but ECT PID is not same as temperature 
gauge reading, inspect ECT sensor.
If temperature gauge on instrument cluster indicates 
overheating but ECT PID is normal, inspect 
temperature gauge and heat gauge unit.

10

Verify test results.

• If okay, return to diagnostic index to service any additional symptoms.

• If malfunction remains, replace PCM.

STEP

INSPECTION

RESULTS

ACTION

18

COOLING SYSTEM CONCERNS     -RUNS COLD

DESCRIPTION

Engine takes excessive period for reaching normal operating temperature.

POSSIBLE CAUSE

• Thermostat malfunction

• Condenser fan system malfunction

• Cooling fan system malfunction

STEP

INSPECTION

RESULTS

ACTION

1

Is customer complaint "Lack of passenger 
compartment heat" only?

Yes

Inspect A/C and heater system.

No

Go to next step.

2

Does engine speed continue at fast idle?

Yes

Go to symptom troubleshooting "No.9 Fast idle/runs 
on".

No

Go to next step.

3

Remove thermostat and inspect operation.
(See 

E–7 THERMOSTAT REMOVAL/

INSTALLATION

.)

(See 

E–8 THERMOSTAT INSPECTION

.)

Is thermostat okay?

Yes

Go to next step.

No

Replace thermostat.

4

Inspect cooling fan control system operation.
(See 

F–234 Cooling Fan Control System 

Inspection

.)

Does cooling fan control system work properly?

Yes

Access ECT PID.
Inspect for both ECT PID and temperature gauge on 
instrment cluster readings.
If temperature gauge on instrument cluster indicates 
normal range but ECT PID is not same as temperature 
gauge reading, inspect ECT sensor.
If temperature gauge on instrument cluster indicates 
cold range but ECT PID is normal, inspect temperature 
gauge and heat gauge unit.

No

Repair or replace malfunctioning part.

5

Verify test results.

• If okay, return to diagnostic index to service any additional symptoms.

• If malfunction remains, replace PCM.

TROUBLESHOOTING 

F–217

F

NO.19 EXHAUST SMOKE

A6E398018881W21

Diagnostic procedure

19

EXHAUST SMOKE

DESCRIPTION

Blue, black, or white smoke from exhaust system

POSSIBLE CAUSE

Blue smoke (Burning oil):

• PCV valve malfunction

• Engine internal oil leakage

White smoke (Water in combustion):

• Cooling system malfunction (coolant loss)

• Engine internal coolant leakage

Black smoke (Rich fuel mixture):

• Air cleaner restriction

• Intake-air system is collapsed or restricted.

• Fuel return line is restricted.

• Excessive fuel pressure

• Improper engine compression

• Injector fuel leakage

• Ignition system malfunction

Warning
The following troubleshooting flow chart contains fuel system diagnosis and repair 
procedures. Read following warnings before performing fuel system services:

• Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always 

keep sparks and flames away from fuel.

• Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injuries or 

death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete 
“BEFORE REPAIR PROCEDURE” and “AFTER REPAIR PROCEDURE” described in this 
manual.
(See 

F–17 BEFORE REPAIR PROCEDURE

.)

(See 

F–17 AFTER REPAIR PROCEDURE

.)

Caution

• Disconnecting/connecting quick release connector without cleaning it may possibly cause 

damage to fuel pipe and quick release connector. Always clean quick release connector 
joint area before disconnecting/connecting, and make sure that it is free of foreign material.

STEP

INSPECTION

RESULTS

ACTION

1

What color is smoke coming from exhaust 
system?

Blue

Burning oil is indicated.
Go to next step.

White

Water in combustion is indicated.
Go to Step 3.

Black

Rich fuel mixture is indicated.
Go to Step 4.

2

Remove and shake PCV valve.
Does PCV valve rattle?

Yes

Inspect for following:

• Damaged valve guide, stems or valve seals

• Blocked oil drain passage in cylinder head

• Piston ring is not seated, seized or worn.

• Damaged cylinder bore

If other drivability symptoms are present, return to 
diagnostic index to service any additional symptoms.

No

Replace PCV valve.

3

Does cooling system hold pressure?

Yes

Inspect for following:

• Cylinder head gasket leakage

• Intake manifold gasket leakage

• Cracked or porous engine block

If other drivability symptoms are present, return to 
diagnostic index to service any additional symptoms.

No

Inspect for cause.

4

Inspect for following:

• Air cleaner restriction

• Collapsed or restricted intake-air system

• Restricted fuel return line

Are all items okay?

Yes

Go to next step.

No

Service as necessary.
Repeat Step 4.

5

Connect WDS or equivalent to DLC-2.
Retrieve any continuous memory, KOEO and 
KOER DTCs.
Are there any DTCs displayed?

Yes

DTC is displayed:
Go to appropriate DTC test.

No

No DTC is displayed:
Go to next step.