I'm the owner ofMAZDA 6 diesel, 89kW, 10 years old, 170k km.

Last week yellowcheck engine light started to blink for few seconds and the engine behavedstrange i.e. I couldn't accelerate the car for these few seconds. Then I turnedoff the car and after 1 minute I started the car again and without any problemsI drove the car few miles. But day after, again yellow check engine lightstarted to blink for few seconds and the engine behaved strange i.e. I couldn'taccelerate the car for these few seconds.

Then I gave myMAZDA 6 on computer testing which shown these 2 problematic codes : P0304-FF-PCM(Cylinder No.4 misfire detection) and P0342-FF-PCM (CMP sensor circuit lowinput).

Can anyone helpasap with the clear explanation what is most likely the reason for theseproblems and codes and what is therecommendation to do to repair the car cheaply?

FYI, below is theexplanation of these 2 problematic codes : P0304-FF-PCM (Cylinder No.4 misfiredetection) and P0342-FF-PCM (CMP sensor circuit low input).

Thank you verymuch

//Miro



DTC P0304 Cylinder No.4 misfire detection

DETECTION CONDITION

The PCM monitorsthe CKP sensor input signal interval time. The PCM calculates the deviation ofthe interval time for each cylinder. If the deviation of the interval timeexceeds the preprogrammed criteria, the PCM detects a misfire in thecorresponding cylinder. While the engine is running, the PCM counts the numberof misfires and calculates misfire ratio for each crankshaft revolution. If theratio exceeds the preprogrammed criteria, the PCM determines that a misfire,which can affect emission performance, has occurred.

Diagnosticsupport note

• The MILilluminates if the PCM detects the above malfunction condition in the firstdrive cycle.

• FREEZE FRAMEDATA is available.

• The DTC isstored in the PCM memory.

POSSIBLE CAUSE

• Fuel injectormalfunction

• CKP sensormalfunction

• CMP sensor malfunction

• Inadequateengine compression due to engine internal malfunction

• Relatedconnector or terminal malfunction

• Related wiringharness malfunction

DTC P0342 CMP sensor circuit low input

DETECTION CONDITION

The PCM monitorsthe input signal from the CMP sensor and the CKP sensor while the engine isrunning. If the input signal from the CMP sensor is not input while the PCM detects255 pulses from the CKP sensor, the PCM determines that there is a malfunctionin the CMP sensor circuit.

Diagnosticsupport note

• The MILilluminates if the PCM detects the above malfunction condition in the firstdrive cycle.

• FREEZE FRAMEDATA is available.

• The DTC isstored in the PCM memory.

POSSIBLE CAUSE

• CMP sensormalfunction

• Connector orterminal malfunction

• Short to GND inwiring harness between CMP sensor terminal A and PCM terminal 81

• Short to GND inwiring harness between CMP sensor terminal B and PCM terminal 55

• Open circuit inwiring harness between CMP sensor terminal A and PCM terminal 81

• Open circuit inwiring harness between CMP sensor terminal B and PCM terminal 55

• Improper CMPsensor air gap

• CMP sensorpulsar malfunction

• PCM malfunction

 

Misfire on a Diesel. Diesel has no spark plugs!
Clean the fuel injectors (put in fuel injector cleaner for diesels?).
Fuel Filters? Change them.

DPF?

Lastly check for leaking air intercooler.

 

Hi, thnx for replying...
FYI, I put fuel injector cleaner for diesels.
I will gave my Mazda to some diesel expert to test for all possible causes.

Why you think DPF could be the reason?

Any other possible causes for these problems?

 

A plugged DPF in the exhaust could cause poor circulation of exhaust.
**** poor exhaust flow could cause a misfire.

 

You wanted other suggestions, here you go. This is a catch all list, not just for diesels.
I got this list from a mechanic and personally dealt with poor exhaust flow which caused my misfire!

Missfires Can Be Caused By a Million and One Things,

Vac Leaks
Wiring Issues
Spark Plugs(Even Fresh Spark Plugs That Are Crappy Quality.... E3 And Such)
Ignition Coils
Alternators (Search EMI)
MAFS
Injectors
Injector O-Rings
Intake Gaskets
TB Gaskets
PCV Hoses
PCV’s
Malfunctioning EGR
Malfunctioning CAS
O2 Sensors
Aftermarket Intakes
Intake Hoses
Vac Lines
Timing Chains
Timing Chain Tensioner
Broken Cam Gears
Malfunctioning Cam Sensors
Incorrect Crank Gears(The I4 Has Like 40 Different Configurations For Whatever Reason)
Incorrect PCM Flash
Issues Within The PCM
PCM Wiring
Bad Diaphram Within The FPR
Issues Within The Fuel Pump
Dirty Fuel Filter
Dirty Fuel Lines
Pre-Cats/Poor Exhaust Flow

If the above gaskets/seals have not been changed, change them. Clean your MAF sensor, throttle body.
Change your PCV valve and probably that short hose as well.
Inspect the intake accordian tube for cracks. Inspect for vaccuum leaks.
Put in a good Fuel system cleaner: Red Line Synthetic Oil - Gasoline Fuel Additives - SI-1 Complete Fuel System Cleaner
Inspect wires. Re-set ECU after doing above.

 

OK...thnx man!

 

It seems 2 Denso injectors are problematic... since they failed on injector's tests so I need to swap them with 2 new Denso injectors RF5C 13 H50 095000 7850

 

I guess fuel injector cleaner wasn't enough for hi mileage vehicle.
Short trips don't help either.
Thanx for the update.
Should change them all while you are there, or get others professionally cleaned.