Hello,

So I have these error codes and I have no clue what to do from now. The P0304 code is the Cylinder 4 misfire detected, P0204 is the Injector Circuit Malfunction - Cylinder 4, and the P0420 is Catalyst System Efficiency Below Threshold (bank 1). So the P0420 code was on before the cylinder 4 codes, could this be related by any chance? I doubt it but I'm not an expert and this is the first time I have ever gotten this code from any dodge that I have owned.

Anyways on to the Cylinder 4 codes. About a week ago my 2007 dodge caliber's check engine light turned on and started flashing when I turned my car on to go to work. It was really cold that day. (does that make a difference?) At first I though my car needed engine oil cause I heard knocking, engine oil is at its range, so not that. I checked the codes and I did not get the P0204 code that first week. So I changed the spark plugs, rotated the coils, rotated the injectors, tested the wires for both the coils and injectors and nothing changed the symptoms. The symptoms: knocking noise, misfire (like the car is about to shut off for lack of fuel), rough run, shaking car, and check engine light flashing. The wierd thing about it was after doing all the pleliminary testing, I drove the car with the check engine light around the block and all of the sudden the car sounded and felt like it was normal. No knocking noise, no roughness, no shaking, no misfire feel, and the check engine light stopped flashing! So I cleared the code and drove the car around during a few trips and it was normal as if I just bought the car from the dealer.

Now a week later, the symptoms are back and with a P0204 code along with them. I feel as if I have ruled out the spark plugs and the injectors and coils being an issue because I changed and rotated them, so if it was a bad injector or coil, the misfire would have changed cylinders, which it did not. I also added the fuel injector additive and have been running the car on premium fuel. And the symptom only happens when I start the car, after driving it around the block a few times, it goes away and the car drives like brand new? The PCM software was updated 5/28/08. I called my local dodge dealer to see if there were any new updates and they said no. And I'm SOL on the warranty because I'm at 96,000 miles already.

So if anyone knows of something I am missing or any suggestions, the comments will be GREATLY appreciated! Thank you, Happy Thanksgiving!

 

Welcome to the forum and happy thanksgiving to you too!!

I suspect that the P0420 is caused by raw fuel getting into the exhaust from cyl#4 not firing. This would cause the cat to not clean the exhaust properly. This leads me to believe that it is perhaps a spark issue.
On the other hand, I am also suspecting the pcm may have an injector driver failing and it may be causing #4 injector to stay wide open, thus filling the cylinder with raw fuel which will cause the plug to foul, partially hydrolock the cylinder, causing the noise and fouling the converter causing the P0420 code. You would need a noid light to check the injector signal. I bought mine at AutoZone for under $20. When you start the car with the noid light in the injector plug, it should have a nice steady flicker as the injector should be pulsing. If the light is very bright and steady, then the injector driver in the PCM is sticking wide open which will dump way too much fuel into the cylinder.
I have had a repaired a couple of cars that did this by replacing the PCM. They were both Ford products, but it could happen to any EFI vehicle.

 

Thank you. I'm calling AutoZone right now to see if they have the light. I have been suspecting that it is the PCM, but wasn'nt sure how to proceed. I will let you know how it goes if I find a light. Sucks cause the part is going to cost over $300 and another $150 to program the pcm at the dealer.

 

Yeah, Good luck, those pcm's ain't cheap!!

 

I had the same issue with my 99 ram 1500 on cylinder 6. It indeed was the computer. Look online for rebuilt computers. I found a company in Ft. Lauderdale Florida that specializes in rebuilt computers. I contacted them and they sent me a computer for my truck. They send an envelope to return your old computer in. I plugged the rebuilt computer in and it worked great. There was no need to have it programmed by the dealer. If I remember right, it cost me about 275.00 for the rebuilt computer. They also give a 12 month warranty on the rebuilt computer.

 

Might work, these newer ones are vin specific these days and must be mated to the instrument cluster so that they match or the security system will not allow the car to start and run.