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Diagnostic procedure

WARNING: This page is about a different car, the 2009 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
STEP INSPECTION RESULTS ACTION
1 Remove all the spark plugs.
Inspect the spark plug condition.
Are the spark plugs conditions normal?		 Yes Troubleshooting completed.
No Specific plug is wet or covered with carbon: 
Go to the next step
Specific plug looks grayish white: 
Go to Step 7.
All plugs are wet or covered with carbon: 
Go to Step 9.
All plugs look grayish white: 
Go to Step 15
2 Are the spark plugs wet/covered with carbon from the engine oil? Yes Inspect all areas related to oil, working up and down.
No Go to the next step.
3 Inspect the spark plugs for the following
  • Cracked insulator
  • Heat range
  • Air gap
  • Worn electrode

Are the spark plugs normal?		 Yes Go to the next step
No Replace the spark plug
(See SPARK PLUG REMOVAL/INSTALLATION [L5] .)
4 Inspect the compression pressure at the suspected malfunctioning cylinder
Is the compression pressure correct?
(See COMPRESSION INSPECTION [L5] .)		 Yes Go to the next step.
No Repair or replace the malfunctioning part.
5 Install all the spark plugs.
Perform the spark test at the suspected malfunctioning cylinder.
Is a strong blue spark visible? (Compare with normal cylinder)		 Yes Go to the next step.
No Repair or replace the malfunctioning part.
6 Inspect the fuel line pressure
(See FUEL LINE PRESSURE INSPECTION [L5] .)
Is the fuel line pressure correct?		 Yes Inspect fuel injector for the following:
  • Open or short circuit in injector
  • Leakage
  • Injection volume
No Zero or low: 
Inspect the fuel pump relay and fuel pump circuit.
Inspect the fuel line for clogging.
If there is no malfunction, replace the fuel pump unit.
(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L5] .)
High: 
Replace the fuel pump unit.
(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L5] .)
7 Inspect the spark plug for the following:
  • Heat range
  • Air gap

Is the spark plug normal?		 Yes Go to the next step.
No Replace the spark plug.
(See SPARK PLUG REMOVAL/INSTALLATION [L5] .)
8 Remove the suspected fuel injector. Inspect the following:

Are all the above items normal?		 Yes Inspect for an open circuit in the wiring harness between fuel injector connector terminal A and the PCM at the following terminals:
  • For No. 1 cylinder: 2BB
  • For No. 2 cylinder: 2BC
  • For No. 3 cylinder: 2BD
  • For No. 4 cylinder: 2AZ
No Replace the fuel injector.
(See FUEL INJECTOR REMOVAL/INSTALLATION [L5] .)
9 Is the air cleaner element free of clogging? Yes Go to the next step.
No Replace the air cleaner element.
10 Perform the spark test.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .)
Is a strong blue spark visible at each cylinder?		 Yes Go to the next step.
No Repair or replace the malfunctioning part.
11 Inspect the fuel line pressure.
(See FUEL LINE PRESSURE INSPECTION [L5] .)
Is the fuel line pressure correct?		 Yes Go to the next step.
No Zero or low: 
Inspect the fuel pump relay and fuel pump circuit. Inspect the fuel line for clogging.
If there is no malfunction, replace the fuel pump unit.
(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L5] .)
High: 
Replace the fuel pump unit.
(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L5] .)
12 Inspect the following PIDs.
  • ECT
  • O2S11 (When engine can be started.)
  • O2S12 (When engine can be started.)
  • MAF

(See PCM INSPECTION [L5] .)
Are the PIDs normal?		 Yes Go to the next step.
No Repair or replace the malfunctioning part.
13 Perform the purge control inspection. (When engine can be started.)
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .)
Is the purge control correct?		 Yes Go to the next step.
No Repair or replace the malfunctioning part.
14 Perform the compression inspection
(See COMPRESSION INSPECTION [L5] .)
Is the compression correct?		 Yes Visually inspect for deformed exhaust system parts
No Repair or replace the malfunctioning part.
15 If the engine cannot be started, inspect the intake air system for air leakage.
If the engine can be started, perform the intake manifold vacuum inspection
Is air sucked in from intake air system?		 Yes Repair or replace the malfunctioning part
No Go to the next step
16 Inspect the fuel line pressure
(See FUEL LINE PRESSURE INSPECTION [L5] .)
Is the fuel line pressure correct?		 Yes Inspect the following PIDs:
  • ECT
  • O2S11
  • O2S12
  • MAF

(See PCM INSPECTION [L5] .)
Inspect PCM ground condition
No Zero or low: 
Inspect the fuel pump relay and fuel pump circuit Inspect the fuel line for clogging.
If there is no malfunction, replace the fuel pump unit.
(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L5] .)
High: 
Replace the fuel pump unit
(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L5] .)
17
  • Verify test results.
    • If normal, return to the diagnostic index to service any additional symptoms

      (See SYMPTOM DIAGNOSTIC INDEX [L5] .)

    • If the malfunction remains, inspect the related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis.
      • If the vehicle is repaired, troubleshooting is completed
      • If the vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if a later calibration is available. Retest.
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