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Home >> Mazda >> 2012 >> 6 i Touring >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 7 (Symptom Troubleshooting [Engine Control System - MZI 3.7 V6]) >> No. 29 Spark Plug Condition >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different variant/trim than selected.
STEP INSPECTION RESULTS ACTION
1 VERIFY SPARK PLUG CONDITION 
 Yes Symptom 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 DETERMINE IF MALFUNCTION CAUSE IS ENGINE OIL LOSS OR OTHER 
  • Are the spark plug wet/covered with carbon by the engine oil?
 Yes Inspect all areas related to oil, working up and down.
No Go to the next step.
3 INSPECT SPARK PLUG 
  • Inspect the spark plug for the following:
    • Cracked insulator
    • Heat range
    • Air gap
    • Worn electrode
  • Is the spark plug normal?
 Yes Go to the next step.
No Replace the spark plug.
(See SPARK PLUG REMOVAL/INSTALLATION .)
4 INSPECT ENGINE COMPRESSION 
  • Inspect the compression pressure at suspected malfunctioning cylinder.

    (See COMPRESSION INSPECTION .)

  • Is the compression pressure correct?
 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
5 INSPECT IGNITION SYSTEM OPERATION 
 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
6 INSPECT FUEL LINE PRESSURE 
  • Install the fuel pressure gauge between the fuel pipe and fuel distributor.
  • Measure the fuel line pressure.

    (See FUEL LINE PRESSURE INSPECTION .)

  • Is the fuel line pressure correct?
 Yes Inspect the fuel injector for the following:
  • Open or short circuit in injector
  • Leakage
  • Injection volume

Repair or replace the malfunctioning part according to the inspection results.
No Zero or low:
  • Inspect for the following:
    • Fuel pump relay
    • Fuel pump circuit
    • Fuel line for clogging

High:
7 INSPECT SPARK PLUG 
  • 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 .)
8 INSPECT FUEL INJECTOR OPERATION 
 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
9 INSPECT AIR CLEANER ELEMENT 
  • Is the air cleaner element free of clogging?
 Yes Go to the next step.
No Replace the air cleaner element.
10 INSPECT IGNITION SYSTEM OPERATION 
 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
11 INSPECT FUEL LINE PRESSURE 
  • Install the fuel pressure gauge between the fuel pipe and fuel distributor.
  • Measure the fuel line pressure.

    (See FUEL LINE PRESSURE INSPECTION .)

  • Is the fuel line pressure correct?
 Yes Go to the next step.
No Zero or low:
  • Inspect for the following:
    • Fuel pump relay
    • Fuel pump circuit
    • Fuel line for clogging

High:
12 VERIFY CURRENT INPUT SIGNAL STATUS 
  • Access the following PCM PIDs:

    (See ON-BOARD DIAGNOSTIC TEST .)

    • ECT
    • O2S11 (When engine can be started.)
    • O2S12 (When engine can be started.)
    • O2S21 (When engine can be started.)
    • O2S22 (When engine can be started.)
    • MAF
  • Are all PIDs normal?

    (See PCM INSPECTION .)

 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
13 INSPECT PURGE CONTROL SYSTEM OPERATION 
 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
14 INSPECT ENGINE COMPRESSION 
 Yes Visually inspect for deformed exhaust system part.
Repair or replace the malfunctioning part according to the inspection results.
  • If normal, replace the fuel. (Poor quality fuel is used.)
No Repair or replace the malfunctioning part according to the inspection results.
15 INSPECT INTAKE-AIR SYSTEM FOR AIR SUCTION 
  • Inspect the following:
    • Intake-air system for air leakage (When the engine cannot be started.)
    • Intake manifold vacuum (When the engine can be started.)
  • Is air sucked in from intake-air system?
 Yes Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
16 INSPECT FUEL LINE PRESSURE 
  • Install the fuel pressure gauge between the fuel pipe and fuel distributor.
  • Measure the fuel line pressure.

    (See FUEL LINE PRESSURE INSPECTION .)

  • Is the fuel line pressure correct?
 Yes Go to the next step.
No Zero or low:
  • Inspect for the following:
    • Fuel pump relay
    • Fuel pump circuit
    • Fuel line for clogging

High:
17 VERIFY CURRENT INPUT SIGNAL STATUS 
  • Access the following PCM PIDs:

    (See ON-BOARD DIAGNOSTIC TEST .)

    • ECT
    • O2S11 (When engine can be started.)
    • O2S12 (When engine can be started.)
    • O2S21 (When engine can be started.)
    • O2S22 (When engine can be started.)
    • MAF
  • Are all PIDs normal?

    (See PCM INSPECTION .)

 Yes Inspect the PCM ground condition.
Repair or replace the malfunctioning part according to the inspection results.
No Repair or replace the malfunctioning part according to the inspection results.
18 Verify test results.
  • If normal, return to diagnostic index to service any additional symptoms.

    (See SYMPTOM DIAGNOSTIC INDEX .)

  • If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis.
    • If vehicle is repaired, troubleshooting completed.
    • If 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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