Mazda 6. Manual - part 176

F–226

TROUBLESHOOTING 

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6

Carry out fuel line pressure inspection.
Is fuel line pressure correct? 

Yes

Inspect fuel injector for following:

• Open or short in injector

• Leakage

• Injection volume

No

Zero or low:
Inspect fuel pump circuit.
Inspect for fuel pump relief valve open.
Inspect for fuel leakage inside pressure regulator.
Inspect for clogged main fuel line.
High:
Inspect pressure regulator for high pressure cause.
Inspect for clogged fuel return line.

7

Inspect spark plug for following.

• Heat range

• Air gap

Is spark plug okay?

Yes

Go to next step.

No

Replace spark plug.

8

Remove suspected fuel injector.
Inspect following:

• Resistance

(See 

F–31 FUEL INJECTOR INSPECTION

.)

• Fuel injection volume

(See 

F–31 FUEL INJECTOR INSPECTION

.)

Are all above items okay?

Yes

Inspect for open circuit between suspected fuel injector 
connector terminal and PCM connector following 
terminals:

• For #1 or #4 cylinder: 1A

• For #2 or #3 cylinder: 1B

No

Replace fuel injector.

9

Is air cleaner element free of restrictions?

Yes

Go to next step.

No

Replace air cleaner element.

10

Carry out spark test.
Is strong blue spark visible at each cylinder?

Yes

Go to next step.

No

Repair or replace malfunctioning parts.

11

Carry out fuel line pressure inspection.
Is fuel line pressure correct?
(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.

12

Inspect following PIDs.

• ECT

• O2S11 (When engine can be started)

• MAF

(See 

F–45 PCM INSPECTION

.)

Are PIDs okay?

Yes

Go to next step.

No

Repair or replace malfunctioning parts.

13

Carry out purge control inspection. 
(When engine can be started)
(See 

F–233 Purge Control System Inspection

.)

Is purge control correct?

Yes

Go to next step.

No

Repair or replace malfunctioning parts.

14

Carry out compression inspection.
Is compression correct?

Yes

Inspect for clogging in exhaust system.

No

Repair or replace malfunctioning parts.

15

When engine cannot be started, inspect intake-
air system for air leakage.
When engine can be started, carry out intake 
manifold vacuum inspection.
Is air sucked in from intake-air system?

Yes

Repair or replace malfunctioning part.

No

Go to next step.

16

Carry out fuel line pressure inspection.
Is fuel line pressure correct?
(See 

F–20 FUEL LINE PRESSURE 

INSPECTION

)

Yes

Inspect following PIDs.

• ECT

• O2S11

• MAF

(See 

F–45 PCM INSPECTION

.)

Inspect PCM GND condition.

No

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

17

Verify test results.

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

• If malfunction remains, replace or reprogram PCM.

STEP

INSPECTION

RESULTS

ACTION

TROUBLESHOOTING 

F–227

F

INTERMITTENT CONCERN TROUBLESHOOTING

A6E398018881W31

Vibration Method

1. If malfunction occurs or becomes worse while driving on a rough road or when engine is vibrating, perform the 

steps below.

Note

• There are several reasons vehicle or engine vibration could cause an electrical malfunction. Some of the 

things to check for are:
— Connectors not fully seated.
— Wire harnesses not having full play.
— Wires laying across brackets or moving parts.
— Wires routed too close to hot parts.

• An improperly routed, improperly clamped, or loose harness can cause wiring to become pinched 

between parts.

• The connector joints, points of vibration, and places where wire harnesses pass through the fire wall, body 

panels, etc. are the major areas to be checked.

Inspection Method for Switch Connectors or Wires

1. Connect WDS or equivalent to DLC-2.
2. Turn ignition key to ON position (Engine OFF).

Note

• If engine starts and runs, perform the following steps at idle.

3. Access PIDs for the switch you are inspecting.
4. Turn switch on manually.
5. Shake each connector or wire harness a bit 

vertically and horizontally while monitoring the 
PID.

• If PID value is unstable, check for poor 

connection.

Inspection Method for Sensor Connectors or Wires

1. Connect WDS or equivalent to DLC-2.
2. Turn ignition switch to ON position (Engine OFF).

Note

• If engine starts and runs, perform the following steps at idle.

3. Access PIDs for the switch you are inspecting.
4. Shake each connector or wire harness a bit 

vertically and horizontally while monitoring the 
PID.

• If PID value is unstable, check for poor 

connection.

Y3U103WN3

Y3U103WN4

F–228

TROUBLESHOOTING 

Inspection Method for Sensors

1. Connect WDS or equivalent to DLC-2.
2. Turn ignition switch to ON position (Engine OFF).

Note

• If engine starts and runs, perform the following steps at idle.

3. Access PIDs for the switch you are inspecting.
4. Vibrate the sensor slightly with your finger.

• If PID value is unstable or malfunction occurs, check for poor connection and/or poorly mounted sensor.

Inspection Method for Actuators or Relays

1. Connect WDS or equivalent to DLC-2.
2. Turn ignition switch to ON position (Engine OFF).

Note

• If engine starts and runs, perform the following steps at idle.

3. Prepare the Output State Control for actuators or relays that you are inspecting.
4. Vibrate the actuator or relay with your finger for 3 seconds are Output State Control is activated.

• If variable click sound is heard, check for poor connection and/or poorly mounted actuator or relay.

Note

• Vibrating relays too strongly may result in 

open relays.

Water Sprinkling Method

Caution

• Indirectly change the temperature and humidity by spraying water onto the front of the radiator.

• If a vehicle is subject to water leakage, the leakage may damage the control module. When testing 

a vehicle with a water leakage problem, special caution must be used.

If malfunction occurs only during high humidity or rainy/snowy weather, perform the following steps.

1. Connect WDS or equivalent to DLC-2 if you are inspecting sensors or switches.
2. Turn ignition switch to ON position (Engine OFF).

Note

• If engine starts and runs, perform the following steps at idle.

3. Access PIDs for sensor or switch if you are inspecting sensors or switches.
4. If you are inspecting the switch, turn it on manually.
5. Spray water onto the vehicle or run it through a 

car wash.

• If PID value is unstable or malfunction occurs, 

repair or replace part as necessary.

End Of Sie

Y3U103WN5

YMU103WC3

TROUBLESHOOTING 

F–229

F

ENGINE CONTROL SYSTEM OPERATION INSPECTION

A6E398018881W32

Main Relay Operation Inspection

1. Verify that the main relay clicks when the ignition switch is turned to ON position and off.

• If there is no operation sound, inspect the following.

— Main relay (See 

T–24 RELAY INSPECTION

.)

— Harness and connector between ignition switch and main relay terminal A.
— Harness and connector between PCM terminal 2X and main relay terminal E.

Intake Manifold Vacuum Inspection

1. Verify air intake hoses are installed properly.
2. Start the engine and run it at idle.
3. Disconnect the vacuum hose between the intake manifold and purge solenoid valve from the intake manifold 

side.

4. Connect a vacuum gauge to the intake manifold and measure the intake manifold vacuum.

• If not as specified, inspect the following.

Specification

More than 60 kPa {450 mmHg, 18 inHg}

Note

• Air suction can be located by engine speed change when lubricant is sprayed on the area where suction is 

occurring.
— Air suction at throttle body, intake manifold and PCV valve installation points
— Accelerator cable free play
— Fuel injector insulator
— Engine compression

(See 

B–9 COMPRESSION INSPECTION

.)

Idle Air Control System Inspection
Engine coolant temperature compensation inspection

1. Connect WDS or equivalent to the DLC-2.
2. Select the following PIDs.

• ECT

• IAT

• RPM

3. Verify that the engine is in cold condition, then start the engine.
4. Verify that the engine speed decreases as the engine warms up.

• If the engine speed does not decrease or decreases slowly, inspect the following.

— ECT sensor and related harness

(See 

F–53 ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION

.)

— IAC valve and related harness

(See 

F–13 IDLE AIR CONTROL (IAC) VALVE INSPECTION

.)

Load compensation inspection

1. Start the engine and run is at idle.
2. Connect WDS or equivalent to the DLC-2.
3. Verify that P0506, P0507 or P0511 not displayed.

• If P0506, P0507 or P0511 shown, carry out DTC inspection.

(See 

F–67 DTC TABLE

.)

4. Change the duty value of the IAC valve to 100% using the IAC PID.
5. Verify that the idle speed increases.

• If the idle speed does not change, inspect the following.

— IAC valve air passage
— Open or short circuit between IAC valve connector terminals and PCM connector terminals 4G and 4J

6. Select the following PIDs.

• ACSW

• IAC

• PSP

• RPM

Note

• Excludes temporary idle speed drop just after the loads are turned on.