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Home >> Mazda >> 2017 >> CX-5 Grand Select, FWD >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Symptom Troubleshooting - SKYACTIVE-G 2.5L >> No. 10 Low Idle/Stalls During Deceleration >> Diagnostic Procedure

Diagnostic Procedure

DIAGNOSTIC PROCEDURE DESCRIPTION

STEP INSPECTION RESULTS ACTION
1 VERIFY IF MALFUNCTION INCLUDES HARD ENGINE STARTING
  • Is the engine unable to start after it has stalled?
    NOTE:
    • If the ignition is not switched off (to LOCK or ACC) after the engine stalls, and then an engine restart is attempted, the PCM corrects the difference between CKP sensor and CMP sensor signals caused by engine stalling, which may result in more time needed to restart the engine.
Yes If the engine is unable to start, perform the symptom troubleshooting "NO. 3 WILL NOT CRANK" and "NO. 6 CRANKS NORMALLY BUT WILL NOT START".
(See NO. 3 WILL NOT CRANK .)
(See NO. 6 CRANKS NORMALLY BUT WILL NOT START .)
No Go to the next step.
2 VERIFY IF MALFUNCTION INCLUDES ROUGH IDLING
  • Does the engine idle rough?
Yes Perform the symptom troubleshooting "NO. 8 ENGINE RUNS ROUGH/ROLLING IDLE".
(See NO. 8 ENGINE RUNS ROUGH/ROLLING IDLE .)
No Go to the next step.
3 VERIFY PCM DTC Yes Go to the applicable DTC inspection.
(See DTC TABLE [PCM (SKYACTIV-G 2.0, 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 .)
    • APP1
    • APP2
    • BOO
    • CPP (MTX)
    • CPP/PNP (MTX)
    • ECT
    • MAF
    • MAP
    • MAP_V
    • TP_REL
    • O2S11
    • O2S12
    • SHRTFT1
    • LONGFT1
      • ALTT V
  • Do the PIDs indicate the correct values under the malfunction condition? (See PCM INSPECTION .)
Yes Go to the next step.
No APP1, APP2 PIDs are not as specified:
BOO PID is not as specified:
ECT 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:
O2S11, SHRTFT1, LONGFT1 PIDs are not as specified:
O2S12 PID is not as specified:
ALTT V PID is not as specified:
  • Inspect the generator. (See GENERATOR INSPECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5] .)

    Repair or replace the malfunctioning part according to the inspection results.

  • If the malfunction remains:
    • Inspect communication error between TCM and PCM. (ATX)
      • Repair or replace the malfunctioning part according to the inspection results if necessary.
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 .)
  • 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 DETERMINE IF MALFUNCTION CAUSE IS DRIVE-BY-WIRE CONTROL SYSTEM OR OTHER
  • Will the engine run smoothly at part throttle?
Yes Go to Step 8.
No Go to the next step.
7 INSPECT DRIVE-BY-WIRE CONTROL SYSTEM OPERATION Yes Visually inspect the throttle body (damage/scratching).
  • If there is any malfunction:
    • Repair or replace the malfunctioning part according to the inspection results.
  • If there is no malfunction:
    • 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 PURGE CONTROL SYSTEM OPERATION Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
10 INSPECT RELATED PART CONDITION Yes Service if necessary.
  • Repeat this step.
No Go to the next step.
11 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 .)
  • Is the FUEL_PRES PID value approx. 3 MPa {31 kgf/cm2 , 435 psi}?
Yes Go to Step 15.
No Lower than 3 MPa {31 kgf/cm2 , 435 psi}:
  • Inspect the following:
  • If there is any malfunction:
    • Repair or replace the malfunctioning part according to the inspection results.
  • If there is no malfunction:
    • Go to Step 14. Higher than 3 MPa {31 kgf/cm2 , 435 psi}:
  • Go to the next step.
12 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 14.
13 INSPECT FUEL PRESSURE SENSOR Yes Replace the fuel distributor.
(See FUEL INJECTOR REMOVAL/INSTALLATION .)
No Go to Step 15.
14 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 .)
15 INSPECT FUEL PRESSURE (LOW-SIDE)
  • Connect the fuel pressure gauge between fuel pump and high pressure fuel pump.
  • Measure the low side fuel pressure. (See FUEL LINE PRESSURE INSPECTION .)
  • Is the low side fuel pressure within specification?

    Specification:

  • 405-485 kPa {4.13-4.94 kgf/cm2 , 58.8-70.3 psi}
Yes ATX:
  • Go to the next step.

MTX:
  • Go to step 17.
No Inspect the following:
  • Fuel line restriction
  • Fuel filter clogged
    • If there is any malfunction:
      • Repair or replace the malfunctioning part according to the inspection results.
    • If there is no malfunction:
16 INSPECT TCC MECHANISM
  • Inspect the TCC mechanism.
  • Is the TCC mechanism normal?
Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results, then go to Step 24.
17 INSPECT ENGINE COMPRESSION
  • Measure the compression pressure for each cylinder. (See COMPRESSION INSPECTION .)
  • Are compression pressures within specification?
Yes Go to Step 23.
No Go to the next step.
18 INSPECT ELECTRIC VARIABLE VALVE TIMING DRIVER Yes Replace the electric variable valve timing motor/driver.
(See ELECTRIC VARIABLE VALVE TIMING MOTOR/DRIVER REMOVAL/INSTALLATION .)
No Go to the next step.
19 INSPECT ELECTRIC VARIABLE VALVE TIMING MOTOR Yes Replace the electric variable valve timing motor/driver.
(See ELECTRIC VARIABLE VALVE TIMING MOTOR/DRIVER REMOVAL/INSTALLATION .)
No Go to the next step.
20 INSPECT ELECTRIC VARIABLE VALVE TIMING ACTUATOR Yes Replace the electric variable valve timing actuator.
(See ELECTRIC VARIABLE VALVE TIMING ACTUATOR, HYDRAULIC VARIABLE VALVE TIMING ACTUATOR REMOVAL/INSTALLATION .)
No Go to the next step.
21 INSPECT HYDRAULIC VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION Yes Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
22 INSPECT FOR MALFUNCTION DUE TO DEVIATED VALVE TIMING Yes Inspect for the following engine internal parts:
  • Cylinder
  • Piston ring
  • Intake valve
  • Exhaust valve
  • Such as cylinder head gasket
    • If there is any malfunction:
      • Repair or replace the malfunctioning part according to the inspection results.
No Adjust the valve timing to the correct timing.
23 INSPECT RELATED PART CONDITION Yes Service if necessary.
  • Repeat this step.
No Go to the next step.
24 Verify the test results.
  • If normal, return to the diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX .)
  • 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.