Sitting quietly in the car, turn the ignition key to the on position and listen
Did you hear the fuel pump prime the fuel rail (about 2 seconds)?
Have someone crank the engine, feel the fuel injectors for pulses
Check for spark.

If not spark and no injector pulse then may be the crank sensor
If no spark and there is injector pulse then issue is in the ignition system
If there is spark and no injector pulse then fuel system issue

 

I need help,my Hyundai elantra 2009 auto won't start, before now,it stalls intermittently on idle,slow movement and on corner. It throws error code P0339. A technician said it's the ECU,and I can't find a replacement for the ECU, 39120-2B050 Part number. Any assistance?

 

Are you sure the technician got it right?

https://www.obd-codes.com/p0339

Did he test (scan) the crank position sensors?

 

I believe "allegretto" struck a nerve !!
There is a big difference in price between a crank sensor and an ECM. Before the ECM can do it's job it has to get the correct info from the Crank Sensor.
I agree with allegretto, and therefore, you might either get another diagnosis or just replace the crank sensor.

 

thanks for your prompt response,I replaced the crank sensor,the car starts and later stalls and didn't start again,up till now. It was then I got another technician that concluded its ECU. I got another ECU,it didn't start,I was told that I have to get the exact part number,that's where the problem is.

 

he doesn't have the tool to do that,so I bought another one. It starts then later stalls and since then,it refused to start but cranking.

 

You are going to need to go to a mechanic that can actually diagnosis this issue.
Ordinary mechanics are parts changers. That is all they know how to do.
They don't really know how to troubleshoot tough cases.
If the mechanic changed any parts then you will want the old parts back in case they are still good.

Have seen where a power steering sensor kept an engine from running.
The power steering sensor was sending out erroneous voltage spikes
Which in turn kept the crank sensor signal from being clean

Anyway, different vehicle.
Would probably put an oscilloscope on the voltage supply to crank sensor and on the output of the sensor
This way you can see if there is anything going on that is compromising the signal.
Would also need schematics to see what else is on that crank shaft sensor

Good luck

 

Thanks so much. I will go to another mechanic as advised. I appreciate your support.

 

Don't feel badly,
There are some conditions that will not always throw a code AND there some conditions that will throw a completely unrelated code. The object is to know which you have and as stated there are lots of , "people" that have no idea what to do or where to go if they have no code to look at. Because they lack the knowledge of how the system is supposed to function and check it out, they change parts or automatically blame "the blackbox". There are many times unless you have the proper test equipment , you are out of business.
Just think, there is more computer power in today's vehicles than the first space capsule that went to the moon, scary isn't it ?