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Home >> Mazda >> 2011 >> 6 s Touring Plus >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (Symptom Troubleshooting [Engine Mechanical MZR 2.5]) >> No. 4 Hard To Start/Long Crank/Erratic Start/Erratic Crank >> Diagnostic procedure

Diagnostic procedure

WARNING: This page is about a different variant/trim than selected.
DIAGNOSTIC PROCEDURE CHART

STEP INSPECTION RESULTS ACTION
1 INSPECT RELATED PART CONDITION 
  • Inspect the following:
    • Vacuum leakage
    • Proper fuel quality (such as proper octane, contamination, winter/summer blend)
    • Loose bands on intake air system
    • Cracks on intake air system parts
    • Intake air system restriction (such as air cleaner element, fresh air duct)
    • Low or dead battery
    • Charging system
  • Are all items normal?
Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
Repeat Step 1.
2 VERIFY PCM DTC  Yes Go to the appropriate DTC inspection.
(See DTC TABLE .)
No Go to the next step.
3 VERIFY IF MALFUNCTION CAUSE IS OVERHEATING 
  • Is the engine overheating?
Yes Go to the symptom troubleshooting "NO. 17 COOLING SYSTEM CONCERNS-OVERHEATING".
(See NO. 17 COOLING SYSTEM CONCERNS-OVERHEATING .)
No Go to the next step.
4 DETERMINE IF MALFUNCTION CAUSE IS EVAP CONTROL SYSTEM OR OTHER 
  • Disconnect the vacuum hose from purge solenoid valve and plug opening end of vacuum hose.
  • Start the engine.
  • Is the starting condition improved?
Yes Inspect if the purge solenoid valve is stuck open.
Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
5 INSPECT MAF SENSOR 
  • Inspect the MAF sensor for following:
    • Contamination
    • MAF sensor terminal B voltage (ground circuit)
  • Is there any malfunction?
Yes Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
6 INSPECT PCM FOR POOR GROUND 
  • Verify the PCM ground point condition.
  • Is there any ground point looseness or lifting in the PCM?
Yes Repair the ground point looseness and lifting.
No Go to the next step.
7 INSPECT IGNITION SYSTEM RELATED WIRING HARNESS 
  • Inspect the ignition coil related wiring harness condition (intermittent open or short circuit) for all cylinders.
  • Are the wiring harness conditions normal?
Yes Go to the next step.
No Repair or replace suspected wiring harness and connector.
8 INSPECT IGNITION SYSTEM OPERATION  Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
9 VERIFY SPARK PLUG CONDITION 
  • Verify the spark plug conditions when the spark plug removed in Step 8.

    (See SPARK PLUG INSPECTION .)

  • Is spark plug wet, covered with carbon or grayish white?
Yes Spark plug is wet or covered with carbon:
  • Inspect for fuel leakage from fuel injector.

Spark plug is grayish white:
  • Inspect the fuel injector for clogging.

Repair or replace the malfunctioning part according to the inspection results.
No Install the spark plugs on original cylinders.
Go to the next step.
10 INSPECT CKP SENSOR AND PULSE WHEEL 
  • Visually inspect the CKP sensor and teeth of crankshaft pulley.
  • Are the CKP sensor and teeth of crankshaft pulley normal?
Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
11 DETERMINE IF MALFUNCTION CAUSE IS DRIVE-BY-WIRE CONTROL SYSTEM OR OTHER 
  • Attempt to start the engine at part throttle.
  • Does the engine run smoothly at part throttle?
Yes Inspect the drive-by-wire control system operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION .)
Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
12 INSPECT FUEL LINE PRESSURE  Yes Go to the next step.
No Zero or low:
  • Inspect the following:
  • Fuel pump relay
  • Fuel pump circuit
  • Fuel line for clogging
  • If there is no malfunction, replace the fuel pump unit.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION .)
High:
  • Replace the fuel pump unit.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION .)
13 INSPECT FUEL LINE HOLD PRESSURE FOR FUEL LEAKAGE 
  • Is the fuel line pressure held after ignition is off?

(See FUEL LINE PRESSURE INSPECTOR .)
Yes Go to the next step.
No Inspect the fuel injector.
(See FUEL INJECTOR INSPECTION .)
  • If the fuel injector is normal, replace the fuel pump unit.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION .)
14 INSPECT EXHAUST SYSTEM 
  • Visually inspect the exhaust system part.
  • Is there any deformed exhaust system part?
Yes Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
15 INSPECT EGR VALVE FOR STUCK 
  • Inspect the engine condition while tapping the EGR valve housing.
  • Does the engine condition improve?
Yes Replace the EGR valve. (See EGR VALVE REMOVAL/INSTALLATION .)
No Go to the next step.
16 INSPECT STARTING SYSTEM  Yes Inspect for loose connectors or poor terminal contact.
  • If there is no malfunction, remove the EGR valve and visually inspect for a mechanically stuck EGR valve.
No Repair or replace the malfunctioning part according to the inspection results.
17
  • Verify test results.
  • If normal, return to the diagnostic index to service any additional symptoms.

    (See SYMPTOM DIAGNOSTIC INDEX .)

  • If a 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.