Mazda 6. Manual - part 172

F–210

TROUBLESHOOTING 

NO.13 KNOCKING/PINGING-ACCELERATION/CRUISE

A6E398018881W15

Diagnostic procedure

End Of Sie

13

KNOCKING/PINGING - ACCELERATION/CRUISE

DESCRIPTION

Sound is produced when air/fuel mixture is ignited by something other than spark plug (e.g., hot spot in 
combustion chamber).

POSSIBLE CAUSE

• Engine overheating due to cooling system malfunction

• ECT sensor malfunction

• IAT sensor malfunction

• MAF sensor malfunction

• Knock sensor malfunction

• Erratic signal from CMP sensor

• Inadequate engine compression

• Inadequate fuel pressure

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

Connect WDS or equivalent to DLC-2.
Access ECT PID.
Verify ECT PID is less than 116

°C {241°F} 

during driving.
Is ECT PID less than specification?

Yes

Go to next step.

No

Inspect cooling system for cause of overheating.

2

Connect WDS or equivalent to DLC-2.
Access IAT, MAF and SPARKADV PIDs.
Monitor each PID.
(See 

F–45 PCM INSPECTION

.)

Are PIDs okay?

Yes

Go to next step.

No

IAT PID: Inspect IAT sensor
MAF PID: Inspect MAF sensor
SPARKADV PID: Inspect CMP sensor and knock 
sensor.

3

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.

4

Is engine compression correct?

Yes

Go to next step.

No

Inspect for cause.

5

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

Inspect ignition timing.

No

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

6

Verify test results.

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

• If malfunction remains, replace PCM.

TROUBLESHOOTING 

F–211

F

NO.14 POOR FUEL ECONOMY

A6E398018881W16

Diagnostic procedure

14

POOR FUEL ECONOMY

DESCRIPTION

Fuel economy is unsatisfactory.

POSSIBLE CAUSE

• Contaminated air cleaner element

• VIS malfunction (if equipped)

• Engine cooling system malfunction

• Improper ATF level (ATX)

• Weak spark

• Poor fuel quality

• Erratic or no signal from CMP sensor

• Clutch slippage (MTX)

• VTCS malfunction

• Improper variable valve timing control system operation (if equipped)

• Improper coolant level

• Inadequate fuel pressure

• Spark plug malfunction

• PCV valve malfunction

• Brake dragging

• Improper valve timing due to jumping out of timing belt

• Contaminated MAF sensor

• Improper engine compression

• Exhaust system clogging

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

Inspect for following:

• Air cleaner element for contamination

• ATF level

• Fuel quality

• Coolant level

• Brake dragging

• Clutch slippage

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

Access ECT PID.
Drive vehicle while monitoring PID.
(See 

F–45 PCM INSPECTION

.)

Is PID within specification?

Yes

Go to next step.

No

Inspect for coolant leakage, cooling fan and condenser 
fan operations or thermostat operation.

F–212

TROUBLESHOOTING 

End Of Sie

4

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

Yes

Inspect for following:

• Spark plugs malfunction

• CMP sensor is improperly installed.

• Trigger wheel damage 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

5

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.

6

Inspect for VTCS operation.
(See 

F–231 Variable Tumble Control System 

(VTCS) Operation Inspection

.)

Does VTCS work properly?

Yes

Go to next step.

No

Repair or replace malfunctioning parts.

7

Note

• The following test should be performed for 

vehicles with variable valve timing control 
system. Go to next step for vehicles 
without variable valve timing control 
system.

Inspect for variable valve timing control system 
operation.
(See 

F–239 Variable Valve Timing Control 

System Operation Inspection

.)

Does variable valve timing control system work 
properly?

Yes

Go to next step.

No

Repair or replace malfunctioning parts.

8

Note

• The following test should be performed for 

vehicles with VIS. Go to next step for 
vehicles without VIS.

Inspect for VIS operation.
(See 

F–230 VIS Operation Inspection

.)

Does VIS work properly?

Yes

Go to next step.

No

Repair or replace malfunctioning parts.

9

Remove and shake PCV valve.
Does PCV valve rattle?

Yes

Go to next step.

No

Replace PCV valve.

10

Inspect for restriction in the exhaust system.
Is there any restriction?

Yes

Inspect exhaust system.

No

Go to next step.

11

Inspect for contaminated MAF sensor.
Is there any contamination?

Yes

Go to next step.

No

Inspect for cause.

12

Inspect MAF sensor for contamination.
Is there any contamination?

Yes

Replace MAF sensor.

No

Go to next step.

13

Is engine compression correct?

Yes

Inspect valve timing.

No

Inspect for cause.

14

Verify test results.

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

• If malfunction remains, replace PCM.

STEP

INSPECTION

RESULTS

ACTION

TROUBLESHOOTING 

F–213

F

NO.15 EMISSION COMPLIANCE

A6E398018881W17

Diagnostic procedure

15

EMISSION COMPLIANCE

DESCRIPTION

Fails emissions test.

POSSIBLE CAUSE

• Vacuum lines leakage or blockage

• Cooling system malfunction

• Spark plug malfunction

• Leakage from intake manifold

• Erratic or no signal from CMP sensor

• Inadequate fuel pressure

• PCV valve malfunction or incorrect valve installation

• EGR valve malfunction

• Exhaust system clogging

• Fuel tank ventilation system malfunction

• Charcoal canister damage

• Air cleaner element clogging or restriction

• Throttle body malfunction

• Spark leakage from high-tension leads

• Improper air/fuel mixture ratio control operation

• Catalyst converter malfunction

• Engine internal parts malfunction

• Excessive carbon is built up in combustion chamber

• Improper engine compression

• Improper valve timing

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

Inspect for following:

• Vacuum lines for leakage or blockage

• Electrical connections

• Proper maintenance schedule followed

• Intake-air system and air cleaner element 

concerns: obstructions, leakage or dirtiness

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

Is any other drivability concern present?

Yes

Go to appropriate symptom troubleshooting.

No

Go to next step.

4

Connect WDS or equivalent to DLC-2.
Access ECT PID.
Warm up engine and run it at idle.
Verify ECT PID is correct.
(See 

F–45 PCM INSPECTION

.)

Is ECT PID correct?

Yes

Go to next step.

No

Inspect for coolant leakage, cooling fan and condenser 
fan operation or thermostat operation.