Mazda 6. Manual - part 170

F–202

TROUBLESHOOTING 

End Of Sie

NO.10 LOW IDLE/STALLS DURING DECELERATION

A6E398018881W12

Diagnostic procedure

2

Connect WDS or equivalent to DLC-2.
Retrieve any continuous memory DTCs.
Are there any DTCs displayed?

Yes

DTC is displayed:
Go to appropriate DTC test.

No

No DTC is displayed:
Go to next step.

3

Connect WDS or equivalent to DLC-2.
Access ACSW, COLP, CPP, CPP/PNP, TR and 
PSP PIDs.
Monitor each PID.
(See 

F–45 PCM INSPECTION

.)

Are PIDs okay?

Yes

Go to next step.

No

ACSW PID: Inspect A/C switch, refrigerant pressure 
switch and fan switch.
COLP PID: Inspect refrigerant pressure switch (middle 
pressure).
CPP PID: Inspect clutch switch (MTX).
CPP/PNP PID: Inspect neutral switch (MTX)
TR PID: TR switch (ATX).
PSP PID: Inspect P/S pressure switch.

4

Is there air leakage felt or heard at intake-air 
system components while racing engine to 
higher speed?

Yes

Repair or replace parts if necessary.

No

Verify accelerator cable free play.
(See 

F–16 ACCELERATOR CABLE INSPECTION/

ADJUSTMENT

.)

5

Verify test results.

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

• If malfunction remains, replace PCM.

STEP

INSPECTION

RESULTS

ACTION

10

LOW IDLE/STALLS DURING DECELERATION

DESCRIPTION

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

POSSIBLE CAUSE

• Vacuum leakage

• IAC valve malfunction

• Air leakage from intake-air system

• Improper air/fuel mixture ratio control

• Evaporative emission control system malfunction

• TP sensor misadjustment

• TP sensor or related circuit malfunction

• MAF sensor or related circuit malfunction

• Brake switch or related circuit malfunction

• Neutral/clutch switch or related circuit malfunction (MTX)

• TR switch or related circuit malfunction (ATX)

• Improper A/C magnetic clutch operation

STEP

INSPECTION

RESULTS

ACTION

1

• Does engine idle rough?

Yes

Go to symptom troubleshooting "No.8 Engine runs 
rough/rolling idle".

No

Go to next step.

2

Turn off A/C switch and fan switch.
Does A/C magnetic clutch engauge?

Yes

Go to symptom troubleshooting “No.24 A/C is always 
on or A/C compressor runs continuously.“

No

Go to next step.

3

Verify following:

• Proper routing and no damage of vacuum 

lines

• IAC valve is connected properly.

• No air leakage from intake-air system

Are all items okay?

Yes

Go to next step.

No

Service as necessary.
Repeat Step 3.

4

Connect WDS or equivalent to DLC-2.
Retrieve any continuous memory, KOEO and 
KOER DTCs.
Are there any DTCs displayed?

Yes

DTC is displayed:
Go to appropriate DTC test.

No

No DTC is displayed:
Go to next step.

5

Does idle speed drop or stall when 
disconnecting IAC valve?

Yes

Go to next step.

No

Inspect following:

• Circuit from IAC valve to PCM connector terminal 

4G or 4J for open and short

• IAC valve for sticking

If okay, go to next step.

TROUBLESHOOTING 

F–203

F

End Of Sie

6

Disconnect vacuum hose between purge 
solenoid valve and intake manifold from purge 
solenoid valve side.
Plug opening end of vacuum hose.
Drive vehicle.
Does engine condition improve?

Yes

Inspect evaporative emission control system.

No

Go to next step.

7

Connect WDS or equivalent to DLC-2.
Access TP, MAF, VSS, BOO, CPP, CPP/PNP 
and TR PIDs.
Monitor each PID while driving vehicle.
(See 

F–45 PCM INSPECTION

.)

Are PIDs okay?

Yes

Intermittent concern exists.

(See INTERMITTENT CONCERN 

TROUBLESHOOTING.)

No

TP PID: Inspect TP sensor.
MAF PID: Inspect MAF sensor.
VSS PID: Inspect VSS.
BOO PID: Inspect brake switch.
CPP PID: Inspect clutch switch (MTX).
CPP/PNP PID: Inspect neutral switch (MTX).
TR PID: Inspect TR switch (ATX) switch.

8

Verify test results.

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

• If malfunction remains, replace PCM.

STEP

INSPECTION

RESULTS

ACTION

F–204

TROUBLESHOOTING 

NO.11 ENGINE STALLS/QUITS, ENGINE RUNS ROUGH, MISSES, BUCK/JERK, HESITATION/STUMBLE, 
SURGES

A6E398018881W13

11

ENGINE STALLS/QUITS — ACCELERATION/CRUISE
ENGINE RUNS ROUGH — ACCELERATION/CRUISE
MISSES — ACCELERATION/CRUISE
BUCK/JERK — ACCELERATION/CRUISE/DECELERATION
HESITATION/STUMBLE — ACCELERATION
SURGES — ACCELERATION/CRUISE

DESCRIPTION

• Engine stops unexpectedly at beginning of acceleration or during acceleration.

• Engine stops unexpectedly while cruising.

• Engine speed fluctuates during acceleration or cruising.

• Engine misses during acceleration or cruising.

• Vehicle bucks/jerks during acceleration, cruising, or deceleration.

• Momentary pause at beginning of acceleration or during acceleration

• Momentary minor irregularity in engine output

POSSIBLE CAUSE

• A/C system operation is improper.

• Erratic signal or no signal from CMP sensor

• Air leakage from intake-air system parts

• Purge solenoid valve malfunction

• IAC valve improper operation

• EGR valve malfunction

• Erratic signal from CKP sensor

• Low engine compression

• Vacuum leakage

• Poor fuel quality

• Main relay intermittent malfunction

• Throttle body malfunction

• Engine overheating

• Spark plug malfunction

• Improper air/fuel mixture ratio control operation

• Improper VTCS operation

• Spark leakage from high-tension leads

• Air cleaner restriction

• PCV valve malfunction

• Improper valve timing due to jumping out timing belt

• Restriction in exhaust system

• Intermittent open or short in fuel body pump circuit

• Inadequate fuel pressure

• Fuel pump mechanical malfunction

• Fuel leakage from fuel injector

• Fuel injector clogging

• Fuel line restriction or clogging

• Pressure regulator malfunction

• TP sensor misadjustment

• Intermittent open or short of MAF sensor, TP sensor and VSS

• ATX malfunction (ATX)

• Clutch slippage (MTX)

• Improper VTCS operation

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.

• Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injuries or 

death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete 
"BEFORE REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this 
manual.
(See 

F–17 BEFORE REPAIR PROCEDURE

.)

(See 

F–17 AFTER REPAIR PROCEDURE

.)

Caution

• Disconnecting/connecting quick release connector without cleaning it may possibly cause 

damage to fuel pipe and quick release connector. Always clean quick release connector 
joint area before disconnecting/connecting, and make sure that it is free of foreign material.

TROUBLESHOOTING 

F–205

F

Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION

1

Verify for following:

• Vacuum connection

• Air cleaner element

• No air leakage from intake-air system

• No restriction of intake-air system

• Proper sealing of intake manifold and 

components attached to intake manifold: 
such as EGR valve, IAC valve

• Ignition wiring

• Fuel quality (e.g. proper octane, 

contamination, winter/summer blend)

• Electrical connections

• Smooth operation of throttle valve

Are all items okay?

Yes

Go to next step.

No

Service as necessary.
Repeat Step 1.

2

Connect WDS or equivalent to DLC-2.
Retrieve any continuous memory, KOEO and 
KOER DTCs.
If stall, condition exists retrieve continuous 
memory and KOEO DTCs.
Are there any DTCs displayed?

Yes

DTC is displayed:
Go to appropriate DTC test.

No

No DTC is displayed:
Go to next step.

3

Is engine overheating?

Yes

Go to symptom troubleshooting "No.17 Cooling system 
concerns - Overheating".

No

Go to next step.

4

Connect WDS or equivalent to DLC-2.
Access RPM, VPWR, MAF, TP and VSS PIDs.
Drive vehicle with monitoring PIDs.
Are PIDs within specifications?
(See 

F–45 PCM INSPECTION

.)

Yes

Go to next step.

No

RPM PID:
Inspect CKP sensor and related harness for such as 
vibration, intermittent open/short circuit.
VPWR PID:
Inspect for open circuit intermittently.
MAF PID:
Inspect for open circuit of MAF sensor and related wire 
harness intermittently.
TP PID:
Inspect if output signal from TP sensor changes 
smoothly.
VSS PID:
Inspect for open circuit of VSS and related wire 
harness intermittently.

5

Visually inspect CKP sensor and teeth of 
crankshaft pulley.
Are CKP sensor and teeth of crankshaft pulley 
okay?

Yes

Go to next step.

No

Replace malfunctioning parts.

6

Measure gap between CKP sensor and teeth of 
crankshaft pulley.

Specification

0.5—1.9 mm {0.020—0.075 in}

Is gap within specification?

Yes

Go to next step.

No

Adjust CKP sensor.

7

Inspect spark plug conditions.
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 for clogged fuel injector.

No

Install spark plugs on original cylinders.
Go to next step.

8

Remove and shake PCV valve.
Does PCV valve rattle?

Yes

Go to next step.

No

Replace PCV valve.

9

Verify that throttle lever is resting on throttle 
valve stop screw and/or throttle valve orifice 
plug.
Is lever in correct position?

Yes

Go to next step.

No

Adjust if necessary.

10

Inspect for restriction in the exhaust system.
Is there any restriction?

Yes

Inspect exhaust system.

No

Go to next step.