Nissan  Navara, D40 yd25ddt, DPF Light on. (read the whole story not the fault you think it would be!)


A client of ours had mentioned that the vehicle had poor fuel economy and came in for a service we had check a few items such as fuel pressure and the infamous engine breather this vehicle did not have a catch can. 2 weeks later the vehicles DPF light had come on, this is where that fun started to work out what fault codes where displayed and why this could have happened only 2 weeks after checking faults codes and couldn’t find any reason to use more diesel than normal.

Diagnostics:Nissan_Navara_egr faults

The scan tool was used first of to test for fault codes

and as follows

  • P2002  – DPF soot accumulation
  • p0403 – EGR system

The workshop had looked at a few Nissan navara’s in the past and have replaced a few on the v6 diesel engine when the shaft snap’s. This time it was time to scope out the EGR system and actuate the EGR control with the scan tool to check if the EGR is doing what it is supposed to do.


How the system works, a five wire system which consists of EGR feedback or TPS style switch to indicate travel movement and Motor Circuit, controlled by engine ECU.

you would think it would have an EGR fault, based on this navara

Tools Needed.

  • Suitable scan tool to communicate with Denso CR system
  • Oscilloscope
  • 12mm socket and ratchet

Firstly remove the EGR pipe from the electronic EGR valve, this is to inspect when the unit is in operation. Connect scan tool and oscilloscope to the top wire orange (wiring diagram listed below).
start the vehicle with the unit disconnected and then switch of the vehicle during the vehicle switching off the EGR valve should operate, and the scope will show a dc waveform of the ECU control confirming that the power circuit is ok, if the valve moves you are not in the clear just yet. it still can be faulty.

Next to check the EGR valve degree of opening, thinner wires purple grey and purple (from the top) the top purple is 5volt, the grey is the ground circuit and the bottom purple is the output of the EGR valves Degree of opening.

EGR control waveform from engine ecu

EGR control waveform from engine ecu

with ignition switched on we had a voltage of 1.2 volts as the vehicle was started and let run for 15 seconds when switching off the valves feedback would operate. however we think that the EGR feedback never returns back to the same position making it faulty. sometimes when the ignition is turned on the voltage would be 0.6 volts with the valve further open, the system is so confused based on the EGR valve being faulty.

further to add to this you can switch on and off on the ignition and hear the EGR move but the valve never moves which indicated that the worm valve inside the EGR unit is worn/broken  hence the EGR unit not responding during driving conditions

Setting up the scope with 2 channels will confirm that the EGR valves is operated and the valves degree of opening is changing, in our case not moving. also note that the EGR valve can be sticking due to exhaust gas soot build up.

2 channel wave form.insert here

EGR control waveform from engine ecu with tps output from position sensor

EGR control waveform from engine ecu with tps output from position sensor

The real Problem.

after test driving this vehicle a few times to check if there was any progress it always felt as though there was no turbo kicking in, back to the workshop to test the variable vane turbo vacuum and found that the vacuum could not operate as the main vacuum line has a split in it.

Repair by cutting and inserting a vacuum joiner. re test drive. Found that full power is now back to what is expected of a Nissan navara.



Finding the information and using our heads including writing this post took 2.5 hours to complete including retesting after, explain to the client what was wrong another story, but we feel this one is nailed.