Hello fellow enthusiasts, I have a 2005 Mazda 3 2.0, recently the battery seemed low so I let the car run for quite a while and when I got back to park it it was running funny. Turns out #1 and #2 cylinders were dead. I checked spark, good, fuel, spark plugs were wet, checked for compression 150 psi, so I have what is needed to fire those two cylinders. What am I missing? And it ran good before I let it runs for a long time. Thanks

 

Using a Scan Tool connected to the Diagnostic Connector (OBDII) retrieve the DTC (Diagnostic Trouble Codes)

 

No codes set

 

2 cylinders that were as you called "dead" which I presume are not firing? Spark and gas but no fire and good compression! From what you described you should have gotten at least one "P0300-304" cylinder misfire DTC?

I am going to assume that you read that I said to use a Scanner and plug it into the Diagnostic connector right?
If so .......
Health check your ECU. Disconnect any coil connector start engine. You should get a check engine light and when using your scanner properly and connected to the OBDII diagnostic connect retrieve the DTC relating to that cylinder you disconnected for the test.


If your scanner has the option to go look at the monitors as well to see if they are ok or any in none readiness