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Home >> Mazda >> 2016 >> 6 Sport, Automatic Trans >> Repair and Diagnosis >> Engine Performance >> System >> Symptom Troubleshooting - Engine Control System >> No. 14 Poor Fuel Economy >> Diagnostic Procedure
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Diagnostic Procedure

STEP INSPECTION RESULTS ACTION
1 VERIFY IF MALFUNCTION CAUSED BY ENGINE MALFUNCTION 
  • Verify the vehicle engine condition.
  • Can malfunction symptoms other than "NO. 14 POOR FUEL ECONOMY" be verified?
 Yes Go to the applicable symptom troubleshooting.
(See SYMPTOM DIAGNOSTIC INDEX [SKYACTIV-G 2.5] .)
No Go to the next step.
2 INSPECT COOLING SYSTEM FOR MALFUNCTION 
  • Is any cooling system concern (overheating, runs cold) present?
 Yes Perform the applicable symptom troubleshooting.
(See NO. 17 COOLING SYSTEM CONCERNS-OVERHEATING [SKYACTIV-G 2.5] .)
(See NO. 18 COOLING SYSTEM CONCERNS-RUNS COLD [SKYACTIV-G 2.5] .)
No Go to the next step.
3 VERIFY PCM DTC 
 Yes Go to the applicable DTC inspection.
(See DTC TABLE [SKYACTIV-G 2.5] .)
No Go to the next step.
4 VERIFY CURRENT INPUT SIGNAL STATUS 
CAUTION:
  • While performing this step, always operate the vehicle in a safe and lawful manner.
  • When the M-MDS is used to observe monitor system status while driving, be sure to have another technician with you, or record the data in the M-MDS using the PID/DATA MONITOR AND RECORD capturing function and inspect later.
  • Access the following PIDs using the M-MDS:

    (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.5] .)

    • APP1
    • APP2
    • ECT
    • IAT
    • MAF
    • MAP
    • MAP_V
    • TP_REL
  • Do the PIDs indicate the correct values under the malfunction condition?

    (See PCM INSPECTION [SKYACTIV-G 2.5] .)

 Yes Go to the next step.
No APP1, APP2 PIDs are not as specified:
ECT PID is not as specified:
IAT PID is not as specified:
MAF PID is not as specified:
MAP, MAP_V PIDs are not as specified:
TP_REL PID is not as specified:
Repair or replace the malfunctioning part according to the inspection results.
5 DETERMINE IF MALFUNCTION CAUSE IS A/C REQUEST SIGNAL OR OTHER 
  • Access the AC_REQ PID using the M-MDS.

    (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.5] .)

  • Monitor the AC_REQ PID while turning on and off the air conditioner using the switch on the control panel.
  • Does the AC_REQ PID value change from on to off according to switch control panel?
 Yes Go to the next step.
No If the AC_REQ PID is always ON:

If the AC_REQ PID is always OFF:
6 INSPECT COOLING FAN CONTROL SYSTEM OPERATION 
 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
7 INSPECT A/C CUT-OFF CONTROL SYSTEM OPERATION 
 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
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 ENGINE.IG1 7.5 A FUSE 
  • Switch the ignition off.
  • Remove the ENGINE.IG1 7.5 A fuse.
  • Inspect the ENGINE.IG1 7.5 A fuse.
  • Is there any malfunction?
 Yes If the fuse is blown:
  • Refer to the wiring diagram and verify whether or not there is a common connector between ENGINE.IG1 7.5 A fuse and PCM terminal 2H.

      If there is a common connector: 

    • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.
    • Repair or replace the malfunctioning part.

      If there is no common connector: 

    • Repair or replace the wiring harness which has a short to ground.
    • Replace the fuse.

If the fuse is damaged:
  • Replace the fuse.

Go to the next step.
No Reinstall the ENGINE.IG1 7.5 A fuse, then go to the next step.
10 INSPECT IG1 RELAY CIRCUIT FOR SHORT TO POWER SUPPLY 
  • Remove the IG1 relay.
  • Disconnect the PCM connector.
  • Measure the voltage at the IG1 relay terminal C (wiring harness-side).
  • Is the voltage 0 V  ?
 Yes Inspect the IG1 relay.
(See RELAY INSPECTION .)
  • If there is any malfunction:
    • Replace the IG1 relay.
  • If there is no malfunction:
    • Reconnect all disconnected connectors.
    • Go to the next step.
No Refer to the wiring diagram and verify whether or not there is a common connector between IG1 relay terminal C and PCM terminal 2H.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to power supply.
  • Repair or replace the malfunctioning part.

If there is no common connector: 
  • Repair or replace the wiring harness which has a short to power supply.
11 INSPECT RELATED PART CONDITION 
  • Inspect the following:
    • Air cleaner element for contamination
    • Intake-air system restriction
    • Fuel quality (proper octane, contamination, winter/summer blend)
    • Coolant level
    • Clutch slippage (MTX)
    • ATF level (ATX)
    • Brake dragging
    • Tire air pressure
    • Vacuum leakage
    • Fuel leakage
    • MAF sensor contaminated
    • Tires, wheels (large size)
    • Change of intake air system components and exhaust system components
    • Engine operation time is longer than traveled distance
      • Vehicle is driven in congested traffic frequently
      • Left idling for long periods
    • Amount of fuel injection increases
      • Overloaded
      • Frequent acceleration/deceleration
      • Frequently driving on ascending roads
      • Travel distance per one drive is short
    • Driver forgets to switch electronic device off
    • Electronic device is frequently used with engine stopped (no power generation)
    • Vehicle left undriven for long periods
    • Large amount of parasitic draw
    • CKP sensor, intake CMP sensor and exhaust CMP sensor
  • Is there any malfunction?
 Yes Service if necessary.
  • Repeat this step.
No Go to the next step.
12 INSPECT FUEL PRESSURE (HIGH-SIDE) 
  • Start the engine and warm it up completely.
  • Access the FUEL_PRES PID using the M-MDS at idle.

    (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.5] .)

  • Is the FUEL_PRES PID value approx. 3 MPa {31 kgf/cm 2  , 435 psi}  ?
 Yes Go to Step 16.
No Lower than 3 MPa {31 kgf/cm 2  , 435 psi}: 
Higher than 3 MPa {31 kgf/cm 2  , 435 psi}  :
  • Go to the next step.
13 DETERMINE IF MALFUNCTION CAUSE IS FUEL PRESSURE SENSOR OR HIGH PRESSURE FUEL PUMP 
  • Is the vehicle acceleration performance normal?
 Yes Go to the next step.
No Go to Step 15.
14 INSPECT FUEL PRESSURE SENSOR 
 Yes Replace the fuel distributor.
(See FUEL INJECTOR REMOVAL/INSTALLATION [SKYACTIV-G 2.5] .)
No Go to Step 16.
15 INSPECT SPILL VALVE CONTROL SOLENOID VALVE CONTROL CIRCUIT FOR SHORT TO GROUND 
  • Switch the ignition off.
  • Disconnect the high pressure fuel pump and PCM connectors.
  • Inspect for continuity between high pressure fuel pump terminal A (wiring harness-side) and body ground.
  • Is there continuity?
 Yes Refer to the wiring diagram and verify whether or not there is a common connector between high pressure fuel pump terminal A and PCM terminal 1EE.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.
  • Repair or replace the malfunctioning part.

If there is no common connector: 
  • Repair or replace the wiring harness which has a short to ground.

If the malfunction remains:
No Replace the high pressure fuel pump.
(See HIGH PRESSURE FUEL PUMP REMOVAL/INSTALLATION [SKYACTIV-G 2.5] .)
16 INSPECT FUEL PRESSURE (LOW-SIDE) 
Specification: 
  • 405-485 kPa {4.13-4.94 kgf/cm 2  , 58.8-70.3 psi} 
 Yes Go to the next step.
No Inspect the following:
  • Fuel line restriction
  • Fuel filter clogged
17 INSPECT ENGINE COMPRESSION 
Specification: 
  • Compression
    • Standard: 954 kPa {9.73 kgf/cm 2  , 138 psi} (300 rpm) 
    • Minimum: 763 kPa {7.78 kgf/cm 2  , 111 psi} (300 rpm) 
    • Maximum difference between cylinders: 161 kPa {1.64 kgf/cm 2  , 23.4 psi} (300 rpm) 
NOTE:
  • Because the SKYACTIV-G 2.5 retards the intake valve closing timing, compression pressure is low.
 Yes Go to the next step.
No Inspect the following:
  • Damaged valve seat
  • Worn valve stem and valve guide
  • Worn or stuck piston ring
  • Worn piston, piston ring or cylinder
  • Improper intake valve timing
  • Improper exhaust valve timing

Service if necessary.
18 INSPECT IGNITION SYSTEM OPERATION 
 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
19 INSPECT EXHAUST SYSTEM FOR RESTRICTION 
  • Inspect for restriction in the exhaust system and the TWC.
  • Is there any restriction?
 Yes Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
20 INSPECT IF MALFUNCTION CAUSE IS PCV VALVE OR INJECTOR DRIVER (PCM INTEGRATED) 
 Yes Replace the PCV valve.
(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [SKYACTIV-G 2.5] .)
No Injector driver malfunction.

If the problem remains, overhaul the engine.
21 Verify the test results.
  • If normal, return to the diagnostic index to service any additional symptoms.

    (See SYMPTOM DIAGNOSTIC INDEX [SKYACTIV-G 2.5] .)

    • 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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