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fix it man
fix it man, Master Technician
Category: Kia
Satisfied Customers: 17278
Experience:  ASE MASTER CERTIFIED, AA DEGREE AUTO/DIESEL
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I keep getting code 340 cam position sensor circuit a

Customer Question

I keep getting code 340 cam position sensor circuit a malfunction. The car is an 02 optima with the 2.4 dohc 4 cylinder. I replaced the sensor and tested the wiring. The main power feed wire, ground and signal all tested good. But i noticed with the sensor disconnected the signal wire had 5volts and when i plugged it back in it had 12volts.
JA: Which particular sensor are you asking about? And have any trouble codes been triggered?
Customer: Camshaft positon sensor and code po340
JA: Are you fixing your Optima yourself? What have you tried so far?
Customer: Ive done what was explained in my first message
JA: Anything else you want the mechanic to know before I connect you?
Customer: No
Submitted: 5 months ago.
Category: Kia
Expert:  fix it man replied 5 months ago.

Hello, my name is***** readings that you are getting are normal. As for the issue, most of the time you will continue to get this code because of a worn out timing belt or a bad crank sensor. Both will cause this. If the timing belt has not been changed then that is more than likely the issue. If the timing belt has been replaced then it may just need the crank sensor. I hope this helps. Let me know if you need anything else.

Customer: replied 5 months ago.
The crank sensor checked out fine. The ecu signal wire is supposed to have full battery volts when the sensor is plugged in i thought it was only supposed to have the reference if 5volt from the ecm
Expert:  fix it man replied 5 months ago.

You said with it disconnected it has 5 volts? And when you connect it and backprobe it then it shows 12 volts?

Customer: replied 5 months ago.
i thought it seemed a little odd because the crank sensor signal only has 5volts like it should but. The cam sensor harness unplugged had its 5v reference and full 12v when plugged in and back probed
Expert:  fix it man replied 5 months ago.

Does the pink wire show battery voltage?

Customer: replied 5 months ago.
the pink wire has 12v and the black has ground
Expert:  fix it man replied 5 months ago.

Thanks. The other wire is simply the signal wire. It is not a reference wire. This vehicle does not use the 5 volts signal on these sensors.

Customer: replied 5 months ago.
since all the wiring is good should i assume that my "new" sensor is bad?
Expert:  fix it man replied 5 months ago.

The sensor may be bad. How is the timing belt?

Customer: replied 5 months ago.
I will check the timing belt but i think its been changed the car only has 90k on it it was owned by an old woman before me i bought it with 70k on it
Customer: replied 5 months ago.
The timing belt only has 20k on it
Expert:  fix it man replied 5 months ago.

Then it should be fine. Did you double check the sensor to see if it was defective?

Customer: replied 5 months ago.
It has power ground and signal to it. I noticed the coil for cylinders 2 and three had no spark and the one for 1and 4 had spark. So for shits and grins i switched them around and the coil i took off 2 and 3 sparked when plugged into the harness for 1 and 4. But the 2 and 3 harness has power ground and the signal from the computer. So im not understanding why it doesn't work
Expert:  fix it man replied 5 months ago.

Let me check the wiring schematic. It may have a computer problem.

Customer: replied 5 months ago.
Ok thats what i was not hoping to hear,
Expert:  fix it man replied 5 months ago.

Did you check the coil for power at the pink wire?

Customer: replied 5 months ago.
I checked the power ground and the signal all of which were intact
Expert:  fix it man replied 5 months ago.

Thanks. If the computer is not getting the right cam and crank signal then the coil will not fire. You will need to determine why there is no signal from the cam sensor. Does your scan tool have the capability of seeing the cam signal?