Diagnostic Code 0304

Code P0340 means camshaft position sensor circuit malfunction

The diagnostic code P0304 means that a misfire was detected in Cylinder 4. Since you ask about misfiring, I'm assuming the 0340 in the text body was a typo and the 0304 in the subject is correct.

When the DTC says that a misfire was detected in cylinder 4, and the check engine light is on, it means that the system detected at least 1 misfire per

1,000 engine revolutions. If the check engine light is flashing then it detected at least 1 misfire per 200 engine revolutions and you need to get the condition resolved soon before it ruins your catalytic converter.

The DTC does not give you the cause of the condition - it only gives a condition. A cylinder misfire can be caused by a problem with the things you mentioned as well as ignition timing, the wiring between the components you listed and the ECU, and the ECU itself. Rather than taking wild guesses and replacing parts, the smart thing to do would be to check the components. If a spark is intermittent, proper equipment like an oscilloscope is needed to diagnose.

Do you know the actual description of the code? That would help, but unfortunately with most engine misfires it could very well be a number of things. My advice is to check over everything and then start replacing the simple components first (spark plugs, wires, coils, etc). Before you spend money on anything though run some basic tests on the coils and wires and pull the spark plugs to check them out.

Forums

Replacing even simple components without checking to see if they are good or not is usually the most expensive way to fix a car.

Check before replacing!

Ray O,

Thanks for responding to my question! I don't have the testing device that you referred to, but I what I have done is pulled the injector from the cyclinder in question, which appeared to be a little clot. I cleared it up put it back in but the rough idle is still there. My next move is to take it to the dealer for hopefully an honest diagnosis.

By the way the exact description of the DTC code is "P0304, Cyclinder 4, Misfire Detected".

I'd almost bet it's the plug wire.

Al

There are a couple of other easy things you can do also. Lucky for you you're working with one of the front bank cylinders! Try moving the #4 coil to a different cylinder and see what you get. If the misfire code follows the coil to a different cylinder, then you know what is at fault. You can do the same with the spark plug, injector, etc...

The code is, P0340 Camshaft Position Sensor Circuit Malfunction

The entire list of codes is

I'm gonna go out on a limb here, you need a Cam Sensor.

The code means the spark plug isn't working right. I've seen this code come from a broken plug wire.

I think the OP had a typo - the subject said P0304 and the message body said P0340.

I've never heard of a cam position sensor going bad on a Toyota but I have heard of misfires so I took a shot and focused ont he P0304, which turns out the be the code he had.

Yeah, I got that right after I clicked Send.

Does his motor have multiple coils, or does it have a distributor and wires? We have a Ford Escort that gave that code (P0304, 0302 actually) and the #2 plug wire was toast. The Code pretty hit the nail on the head in that case ... I'd suppose a bad coil would give the same code if there was a separate coil for each spark plug.

the subject said P0304 and the message body said

I seem to remember that the older Avalons had a coil on each plug.

I'm pretty the OP's car has a coil for each cylinder.

Then the diagnostics would include the possibility that the respective coil was bad. Perhaps switching the coil to another plug and watch the Code change ...