Before you Start
OK, so you have a problem with your truck. It is tempting to search the internet for those exact symptoms and buy the new part to fix the problem. This might work, but before you start experience tells us that there are a few simple steps that will cure most of the issues you might be having and if not give you a good baseline to progress from.
The YD25 engine
The YD25 engine fitted to the D40 Navara, is powerful and efficient for its size, however to enable it to do so, it has a sophisticated fuelling system with sensors monitoring performance and demands. This means that if the ECU does not see the feedback from one of the sensors it expects to see, the engine will drop into safe running or ‘Limp mode’. (A severe reduction in power to prevent engine damage)
Sometimes (but not always) this limp mode will be accompanied by the amber ‘Check engine warning light’ coming on. Turning the engine off and restarting will normally get it out of limp mode but the reason for the limp mode still needs to be researched at a later time.
Occasionally the engine will suffer misfires, stalling, poor performance or excessive smoking without falling into limp mode or lighting the check engine light.
This guide has been written using information gathered from the forum and the source can be found using the search function.
So to start, try the following in order; it will cost you a lot less than a diagnostic assessment from Mr Nissan and might actually fix the problem.
Change the fuel filter
The fuel filter is easily contaminated (after a dirty or water contaminated fuel fill) and as a result will flow a lot less fuel than the engine demands. There have been problems with cheaper aftermarket filters not working correctly so our advice is to use a genuine Nissan item or a top quality equivalent. The canister type filter used on the 2007 onwards D40, has a Tee piece connector on top with sealing ring. The cheaper filters do not come with this fitted and can allow air into the fuel system. Genuine part No.16400EC00A for the canister (Euro4) type.
Check, possibly change the air filter
The air filter can be blocked by dust, leaves and even water. If in doubt change it. If it is water damaged tell us!
Clean the MAF.
This is also known as the airflow sensor, it is mounted just after the air filter and can become dirty especially if an oiled aftermarket air filter is used.
Try resetting the ECU and reading any fault codes
This is a way of reading the fault codes stored in the vehicles ECU without using an aftermarket code reader. It also resets the ECU to factory settings so may help ‘Injector rattle’, excessive smoke etc.
Turn ignition on so all dash lights come on.
Wait 3 seconds
PUMP accelerator pedal 5 times within 5 seconds....
with foot now OFF accelerator wait 7 seconds...
After 7 seconds press and hold down accelerator pedel for 10 seconds...
After 10 seconds the Engine Management Light will start to flash, at this point remove foot from accelerator.
the Navara is now in diagnostic mode, so let the EML flash for a bit.
Fault codes are 4 digit numbers. (i.e. 0246) The EML light flashes in a sequence of 4 blocks of up to ten flashes. The first number is dictated by the slow flashes and the next three by the fast flashes. For example, 0246 would be ---------- .. …. ……
Take your time and read the flashes a couple of times to be sure.
The press and hold the acclerator pedel down for more than 10 seconds..this will then reset ECU and fuel pump etc......and put them into learning mode. You’ve now finished.
As an alternative to reading the fault codes using this method you can use a code reader. These are readily and cheaply available and you can even get an app for your mobile phone to do this. (This does not reset the ECU though).
If you get a fault code tell us what you get.
Be aware that fault codes are not always a true reflection of what the problem is, although it should give us a good starting point.
Consider fitting a blank to your EGR valve.
The Exhaust Gas Recirculation (EGR) valve is an emissions control device. It operates by bleedingexhaust gasses back through the air intake of the engine at different load situations. There is a lot of discussion about its merits but the upshot for us Navara owners is that it causes carbon deposits in the intake choking the engine and causing premature engine wear. The valve itself has been known to fail due to these carbon deposits and is expensive to repair. The blank piece fits in the supply pipe and costs no more than £5 from Ebay.
It has been pointed out that some 190 models can occasionally throw up a fault code (P0401) relating to the fitment of the blank. There are no other symptoms attached and it is easily cured by an ECU reset.
Do another ECU reset. Possibly a 'Hard reset'