The 2003 Micras have a serious problem with the chain. Actually, it is not the chain that causes all the errors. It's the ECU soft.
Let me explain.
The chain is stretching, that is a fact, but not a major problem. The system finds and signals the chain stretching too often and way too soon. The small piston that is responsable for keeping the chain stretched(i believe it is called hydraulic actuator) has a max. of 20 mm course. Now, when it reaches 8-12 mm out, the ECU soft detects that and signals the driver by CHECK ENGINE light on board.
The engine is running ok though, but you still have an error.
I have the same problem, i changed 3 camshaft sensor by now(2 aftermarket, and an OEM one), but still have this issue.
My mechanic took off everything that is on top of the engine and was able to see and feel the chain. The chain was not loose at all. He wasn't able to actually see the hydraulic actuator, but the fact that the chain was not loose indicates the hydraulic actuator is not at the end of it's course(which is aprox. 20 mm).
The chain is not rattling, makes no noise, the engine runs fine, but i keep getting the P0340 error.
That error appears randomly, most of the time when i keep in 3-rd and go wild... 4000-5500 revs, but not always. Check Engine light comes on, but the engine keeps running like nothing happened.
I learned how to clear the error by using a pattern, standing behind the steering wheel. I am tired spending money on electrician just to clear that error.
So, my conclusion is that the ECU soft is wrongly set to detect and signal this small stretching(starting with only 8 mm course of actuator)
Later models with same engine don't have this problem, at least not so often.
