2005 Hyundai Accent - Camshaft Position Sensor CODE
 

I purchased the car used, not running, timing belt failure. The car has been repaired and no check engine light appears while driving, car accelerates with no hesitation or loss of power, everything else works fine. no other issues.

After I turn off the car and start it back up, the CEL appears and indicates a Camshaft Positions Sensor issue. P0340
I installed new CanPosSens and did not change. If you turn off CEL, start the car,again it quick starts, runs good, good power drive well, no hesitation, no lack of power. Drive it for an hour, no CEL. Turn the car off and start it back up, CEL stays lit, same CamPosSens code. Even after replacing the CamPosSens with a new one.

This is what happens...using a basic code reader, I can shut the code off and it does not reappear so long as idle, checking the code during idle states " no codes found " if I rev the engine, to 1000 rpms...the PO340 code appears on my reader, but does not set the CEL until after restart.

The car starts after two/three revolutions, has good power and acceleration...I have replace the Cam Pos Sens with a new one...no change.

any help on what to check ?

inquiring minds want to know.

There have been times when the alternator sent screwy signals and the cam sensor picked them up , you might try unplugging the alt and try a few times to see if that keeps it off. If it does , you know what you need to do, (just in case repl the alt).

I tried your suggestion to no luck. NOTE: you can have alternator tested and look to see if AC ( Alternating Current ) leak is present.

Second NOTE: the alternator produces alternating current, the diodes changes the AC to DC. It is possible that the diodes can begin to fail, but not completely and they will allow the alternating current to feed into your electrical systems wreaking havoc on DC voltages and causing false-positive errors.

Third NOTE: the rule of thumb on cars, the last thing you did is probably what caused the problem. AKA, i'm gonna rip the front end off the engine and double check the timing....I'm beginning to believe that I got the timing one tooth off. I bought the car not running so i don't know how it is to perform under spec. this is an Auto and i have a second one that is a manual...i thought the difference in the transmissions was responsible for the acceleration difference between them....but in hindsight...this may be error-related thinking on my part. ( hate when I do error-related thinking ) lol.

Paying close attention to what you are telling us could very well be a problem other than the cam sensor only that sensor is picking up the problem.

I don;t know for sure without actually looking at your vehicle, but the PCM sends a bias voltage to all sensors on a string, usually a 5 volt reference voltage. If another sensor is pulling that voltage down because of a possible short , it may not set a code for that particular sensor, but will for the cam sensor.. This is not an uncommon occurrence and requires a good elec savy tech to check it out. This could explain why it only happens when you first turn the key on.

I believe that the cam sensor helps in starting the vehicle
Then after that, the signal isn't really used but is monitored
The cam shaft has a notch that usually tells when one cylinder is at TDC on compression
So the spark and injectors are set correctly
Once engine is started, the ECM no longer needs the cam signal to time the spark and injectors
The ECM just uses the crank shaft sensor to keep the engine running
This is why there is no CEL while idling
And you have good power.
And the CEL doesn't set until you try starting the engine up again.

Could be timing
But, I am more inclined to believe that the cam sensor is not reaching far enough in to read the cam shaft.
Or may be even a wiring issue
This happens on some Hyundai's , especially when the weather gets cold.
The sensor shortens a very small amount but enough to cause hard starts.
Another cause could be a double O-ring on the sensor??

Do not take my word about this.
I am only guessing.
Good luck

I am inclined to agree with avisitor's explanation, since with Hyundais mechanical things are more common than some electrical problems. Makes more sense to check the steps he suggested.first. Let us know what you find., thanks.

according to the rep manual...the CamPosSens is used to time spark. so it is needed so long as the car is running.

I moved the crank so that the timing mark lines up with the " ZERO " on the timing marks indicator on the block. when I removed the CamPosSens and look down, there is a mark on the camshaft and that is pointing at 11 am ( this engine turns counter clockwise and I am standing at the passenger side of the vehicle ). if that mark is suppose to be at 12 noon...then i messed up and this is probably my problem.

At idle the light does not set, but with revs, it does. I assume the mark on the camshaft needs to be at 12 noon.

can anybody say do-over. LOL.

From where I sit, it looks like you found the problem and very shortly will make an effective repair.
Please let us know if this takes care of it, thanks.

Turns out the timing belt is installed correctly, marks on it and it's associated exhaust camshaft are aligned. The problem was the intake cam was over rotated one tooth - there be a chain connecting the two and I did not get that part right. I have reset the intake cam and still have the car apart at this time. Just need to torque the cam bolts and always remember...installation, is the opposite of de-installation.


I am so thankful that I did not have to pull the front end off, cause that is a lot of work requiring removal of the passenger side engine mount and water pump pulley.