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NO.10 LOW IDLE/STALLS DURING DECELERATION [SKYACTIV-G 2.0]

10

LOW IDLE/STALLS DURING DECELERATION

DESCRIPTION

  • Engine stops unexpectedly at beginning of deceleration or recovery from deceleration.

POSSIBLE CAUSE

  • PCM DTC is stored

  • Erratic signal to PCM

    • APP sensor or related circuit malfunction

    • Brake switch or related circuit malfunction

    • CPP switch or related circuit malfunction (MT)

    • Neutral switch or related circuit malfunction (MT)

    • Communication error between TCM and PCM (AT)

    • ECT sensor No.1 or related circuit malfunction

    • MAF sensor or related circuit malfunction

    • MAP sensor or related circuit malfunction

    • A/F sensor or related circuit malfunction

    • HO2S or related circuit malfunction

    • TP sensor or related circuit malfunction

    • Generator malfunction (part, system, control malfunction)

      • Amount of generator voltage is large

    • Improper air/fuel mixture ratio control

  • Improper operation of A/C magnetic clutch

  • Improper operation of drive-by-wire control system

  • Incorrect fuel injection timing

  • Fuel injector malfunction

  • Purge solenoid valve malfunction

  • Poor fuel quality

  • Air leakage from intake-air system

  • Vacuum leakage

  • Intake-air system restriction

  • Fuel leakage

  • Engine mount installation loose

  • Erratic signal from CKP sensor

    • Loose installation

    • Damaged trigger wheel (crankshaft pulley)

    • Open or short circuit in related wiring harness

  • Erratic signal from intake CMP sensor

    • Loose installation

    • Damaged trigger wheel (intake camshaft)

    • Damaged trigger wheel (exhaust camshaft)

    • Open or short circuit in related wiring harness

  • Inadequate fuel pressure (high or low pressure side)

    • Fuel pressure sensor or related circuit malfunction

    • High pressure fuel pump malfunction

    • Spill valve control solenoid valve control circuit malfunction (damage to driver in PCM caused by short circuit to ground system)

    • Spill valve control solenoid valve (built-into high pressure fuel pump) malfunction

    • Relief valve (built-into high pressure fuel pump) malfunction

    • Fuel line restriction

    • Fuel filter clogged (built-into fuel pump unit)

    • Fuel pump unit malfunction

  • TCC mechanism malfunction (AT)

  • Low engine compression

  • Improper intake valve timing

  • Improper exhaust valve timing

  • Improper operation of electric variable valve timing control system

    • Electric variable valve timing driver malfunction

    • Electric variable valve timing motor malfunction

    • Electric variable valve timing actuator malfunction

  • Improper operation of hydraulic variable valve timing control system

  • Injector driver (built-into PCM) malfunction

POSSIBLE CAUSE

WARNING:

  • The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before performing the fuel system services:

    • Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel.

    • Highly pressurized fuel may spray out if the fuel line is cut. Due to the following dangers occurring with a fuel spray, always complete the “Fuel Line Safety Procedure” to prevent the fuel from spraying. (See BEFORE SERVICE PRECAUTION [SKYACTIV-G 2.0].)

      • Fuel may cause irritation if it comes in contact with skin and eyes.

      • If fuel ignites and causes a fire, it may lead to serious injury or death, and damage to property and facilities.

    • Fuel is highly flammable and dangerous. Fuel line spills and leakage can cause serious injury or death, and damage to equipment. Always refer to the “Quick Release Connector Removal/Installation (fuel system)” before performing the fuel hose installation, and execute the “Fuel Leakage Inspection” after installation. (See QUICK RELEASE CONNECTOR REMOVAL/INSTALLATION [SKYACTIV-G 2.0].) (See AFTER SERVICE PRECAUTION [SKYACTIV-G 2.0].)

CAUTION:

  • Disconnecting/connecting the quick release connector without cleaning it may possibly cause damage to the fuel pipe and quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.

CAUTION:

  • Verify the malfunction symptom according to not only the PID value but also the symptom troubleshooting.

Related PIDs

Item (definition)

Unit/Condition

Definition

Condition/Specification (Reference)

AC_REQ

Off/On

A/C switch status received by PCM via CAN

  • A/C switch on: On

  • A/C switch off: Off

ALTF

%

Field coil current control signal output to generator

  • Ignition switched ON (engine off): 0% (ECT is 80 °C {176 °F})

  • Idle: Approx. 40.41% (ECT is 80 °C {176 °F})

  • Racing (Engine speed is 2,000 rpm): 20.24% (ECT is 82 °C {180 °F})

  • Racing (Engine speed is 4,000 rpm): 16.16% (ECT is 87 °C {189 °F})

  • Idle (A/C on): Approx. 38.98% (ECT is 89 °C {192 °F})

ALTT V

V

Generator output voltage

  • Idle (no E/L): Approx. 14 V (This is internal calculation value and differs from terminal voltage)

APP1

%

Accelerator pedal opening angle (absolute value) input from APP sensor No.1

  • Accelerator pedal released: Approx. 15.29%

  • Accelerator pedal fully depressed: Approx. 90.98%

V

APP sensor No.1 voltage

  • Accelerator pedal released: Approx. 0.77 V

  • Accelerator pedal fully depressed: Approx. 4.55 V

APP2

%

Accelerator pedal opening angle (absolute value) input from APP sensor No.2

  • Accelerator pedal released: Approx. 7.84%

  • Accelerator pedal fully depressed: Approx. 45.49%

V

APP sensor No.2 voltage

  • Accelerator pedal released: Approx. 0.38 V

  • Accelerator pedal fully depressed: Approx. 2.27 V

BOO

High/Low

Brake switch (No.1 signal) input status

  • Brake pedal released: Low

  • Brake pedal fully depressed: High

CPP (MT)

Off/On

Clutch pedal position

  • Clutch pedal released: Off

  • Clutch pedal fully depressed: On

CPP/PNP (MT)

Off/On

Shift lever position

  • Neutral: On

  • Other than neutral: Off

ECT

°C, °F

Engine coolant temperature input from ECT sensor No.1

  • Displays ECT

V

ECT sensor No.1 voltage
    Ignition switched ON (engine off)

  • ECT is 92 °C {198 °F}: Approx. 0.65 V

    Idle (after warm up)

  • ECT is 93 °C {199 °F}: Approx. 0.64 V

    Racing (Engine speed is 2,000 rpm)

  • ECT is 92 °C {198 °F}: Approx. 0.66 V

    Racing (Engine speed is 4,000 rpm)

  • ECT is 93 °C {199 °F}: Approx. 0.64 V

FUEL_PRES

KPa , mBar , psi, in H20

Fuel pressure input from fuel pressure sensor

  • Displays fuel pressure

V

Fuel pressure sensor voltage
    Ignition switched ON (engine off)

  • Fuel pressure is approx. 3.6 MPa {37 kgf/cm2, 522 psi}: Approx. 1.01 V (ECT is 92 °C {198 °F})

    Idle (after warm up)

  • Fuel pressure is approx. 3.45 MPa {35.2 kgf/cm2, 500 psi}: Approx. 1 V (ECT is 92 °C {198 °F})

    Racing (Engine speed is 2,000 rpm)

  • Fuel pressure is approx. 3.21 MPa {32.7 kgf/cm2, 466 psi}: Approx. 0.96 V (ECT is 86 °C {187 °F})

    Racing (Engine speed is 4,000 rpm)

  • Fuel pressure is approx. 5.59 MPa {57.0 kgf/cm2, 811 psi}: Approx. 1.29 V (ECT is 84 °C {183 °F})

LOAD

%

Ratio of actual amount of intake air to the maximum air charging amount (mass volume) of cylinder

  • Idle (after warm up): Approx. 27.05% (ECT is 91 °C {196 °F})

  • Racing (engine speed is 2,000 rpm): Approx. 16.86% (ECT is 89 °C {192 °F})

  • Racing (engine speed is 4,000 rpm): Approx. 17.64% (ECT is 87 °C {189 °F})

LONGFT1

%

Fuel learning correction amount estimated based on A/F sensor signal

  • Idle (after warm up): Approx. −1.56% (ECT is 91 °C {196 °F})

  • Racing (engine speed is 2,000 rpm): 2.34% (ECT is 89 °C {192 °F})

  • Racing (engine speed is 4,000 rpm): 2.34% (ECT is 87 °C {189 °F})

MAF

g/Sec

Mass air flow input from MAF sensor

  • Displays MAF

V

MAF sensor voltage

  • Ignition switched ON (engine off) (MAF: 0.39 g/s {0.052 lb/min}): Approx. 0.72 V (ECT is 89 °C {192 °F})

  • Idle (after warm up) (MAF: 4.29 g/s {0.567 lb/min}): Approx. 1.15 V (ECT is 88 °C {190 °F})

  • Racing (engine speed is 2,000 rpm) (MAF: 4.32 g/s {0.571 lb/min}): Approx. 1.15 V (ECT is 89 °C {192 °F})

  • Racing (engine speed is 4,000 rpm) (MAF: 12.71 g/s {1.681 lb/min}): Approx. 1.66 V (ECT is 89 °C {192 °F})

MAP

KPa , mBar , psi, in H20

Manifold absolute pressure input from MAP sensor

  • Displays MAP

MAP_V

V

MAP sensor voltage

  • Ignition switched ON (engine off) (MAP:101 kPa {1.03 kgf/cm2, 14.6 psi}): Approx. 4.08 V (ECT is 89 °C {192 °F})

  • Idle (after warm up) (MAP: 31 kPa {0.32 kgf/cm2, 4.5 psi}): Approx. 1.25 V (ECT is 88 °C {190 °F})

  • Racing (engine speed is 2,000 rpm) (MAP: 32 kPa {0.33 kgf/cm2, 4.6 psi}): Approx. 1.31 V (ECT is 89 °C {192 °F})

  • Racing (engine speed is 4,000 rpm) (MAP: 49 kPa {0.50 kgf/cm2, 7.1 psi}): Approx. 2.03 V (ECT is 89 °C {192 °F})

O2S11

µA

A/F sensor current

  • Idle (after warm up): −59 µA (ECT is 92 °C {198 °F})

  • Deceleration fuel cut (accelerator pedal released from engine speed of 4,000 rpm or more): Approx. 3.48 mA (ECT is 92 °C {198 °F})

O2S12

V

HO2S voltage

  • Idle (after warm up): 0—1.0 V (ECT is 91 °C {196 °F})

  • Deceleration fuel cut (accelerator pedal released from engine speed of 4,000 rpm or more): Approx. 0 V (ECT is 92 °C {198 °F})

RPM

RPM

Engine speed

  • Displays engine speed

SHRTFT1

%

Fuel feedback correction amount estimated based on A/F sensor signal

  • Idle (after warm up): Approx. 0% (ECT is 91 °C {196 °F})

  • Racing (engine speed is 2,000 rpm): Approx. 0.78% (ECT is 89 °C {192 °F})

  • Racing (engine speed is 4,000 rpm): Approx. −21.87% (ECT is 87 °C {189 °F})

TP_REL

%

Throttle valve opening angle (relative value) with value at throttle valve fully close timing as the start point

  • Accelerator pedal released: Approx. 12.15%

  • Accelerator pedal fully depressed: Approx. 81.96%

VSS

KPH, MPH

Vehicle speed

  • Displays vehicle speed
Diagnostic Procedure

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 [SKYACTIV-G 2.0].)

(See NO.6 CRANKS NORMALLY BUT WILL NOT START [SKYACTIV-G 2.0].)

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 [SKYACTIV-G 2.0].)

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)].)

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.

Yes

Go to the next step.

No

APP1, APP2 PIDs are not as specified:

BOO PID is not as specified:

CPP PID is not as specified: (MT)

CPP/PNP PID is not as specified: (MT)

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:

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

  • If the malfunction remains:

    • Inspect communication error between TCM and PCM. (AT)

      • Repair or replace the malfunctioning part according to the inspection results if necessary.

    • Perform the “INTERMITTENT CONCERN TROUBLESHOOTING” procedure.

      (See INTERMITTENT CONCERN TROUBLESHOOTING [SKYACTIV-G 2.0].)

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 [PCM (SKYACTIV-G 2.0)].)

  • Monitor the AC_REQ PID while turning on and off the air conditioner with 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)

Yes

Go to Step 15.

No

Lower than 3 MPa {31 kgf/cm2, 435 psi}:

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 [SKYACTIV-G 2.0].)

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 [SKYACTIV-G 2.0].)

15

 INSPECT FUEL PRESSURE (LOW-SIDE)
    Specification:

  • 425—505 kPa {4.34—5.14 kgf/cm2, 61.7—73.2 psi}

Yes

Go to the next step.

No

Inspect the following:

  • Fuel line restriction

  • Fuel filter clogged

16

 INSPECT IF MALFUNCTION CAUSE IS ENGINE COMPRESSION OR INJECTOR DRIVER (PCM INTEGRATED)

Yes

Go to Step 22.

No

Go to the next step.

17

 INSPECT ELECTRIC VARIABLE VALVE TIMING DRIVER

Yes

Replace the electric variable valve timing motor/driver.

(See ELECTRIC VARIABLE VALVE TIMING MOTOR/DRIVER REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)

No

Go to the next step.

18

 INSPECT ELECTRIC VARIABLE VALVE TIMING MOTOR

Yes

Replace the electric variable valve timing motor/driver.

(See ELECTRIC VARIABLE VALVE TIMING MOTOR/DRIVER REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)

No

Go to the next step.

19

 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 [SKYACTIV-G 2.0].)

No

Go to the next step.

20

 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.

21

 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.

22

 INSPECT FOR MALFUNCTION DUE TO ENGINE MOUNT INSTALLATION LOOSE

  • Verify the engine mount installation condition.

  • Is the engine mount installation condition normal?

Yes

AT:

  • Go to the next step.

MT:

No

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

23

 INSPECT TCC MECHANISM

  • Inspect the TCC mechanism.

  • Is the TCC mechanism normal?

Yes

Injector driver malfunction.

If the problem remains, overhaul the engine.

No

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

24

Verify the test results.

  • If normal, return to the diagnostic index to service any additional symptoms.

    (See SYMPTOM DIAGNOSTIC INDEX [SKYACTIV-G 2.0].)

  • 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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Free to use workshop manual for your 2015+ Mk4 'ND' Mazda MX-5

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