P0473

[sir-revalot]

Hey guys. I'd like to introduce myself. I'm Paul from Portland Victoria.
So.. I just bought my first Navara. 2011 D40. YD25.
This thing's had a pretty hard life and has spent most of its time near the beach. Problem I have it's throwing a P0473 fault code which is the dpf differential pressure sensor circuit high. I've back probed all of the three terminals and can't find a ground signal. I've also repaired a load of wiring underneath that was melted behind the dpf. The wiring I repaired is for the O2 sensor and the rear EGT sensor. The question I have is should I have a ground at the differential pressure sensor? And what pin should it be. I have grey wire, a blue wire and a green with white trace. Does anyone have a pcm wiring diagram? Is it possible that the pcm could be at fault here? Thanks in advance for your help.

 

[Old.Tony]

The differential pressure sensor should be located high up on the inside of the engine bay, on the vehicle left hand side against the guard tucked into the corner near the bonnet hinge. It's a black widget that has two rubber hoses coming from it that connect to two metal tubes that run down under the car, one to the front of the DPF and the other to the rear. The sensor itself is little more than a hall-effect sensor that detects excessive pressure in one pipe over the other. There is no electrical connection from this sensor to the DPF, it's purely exhaust pressure pushed up a (small - about 10mm diameter) pipe.

The DPF has 3 sensors on it. There are two temperature sensors and one air/fuel ratio sensor. The harness connector for the front temp sensor is white, the connector for the rear is black. I can't tell you what colour the individual wires are.

With that said, it's possible that you've got failed temp sensors (it's surprisingly common). Have a look in this thread for info on getting replacements:

https://www.navaraforum.com/threads...tops-white-smoke-and-prevent-dpf-fault.24501/

 

[sir-revalot]

Thanks @Old Tony. I've found the differential pressure sensor and all the hoses are good. The air fuel ratio sensor and rear temp sensor are the ones that had melted wires. The only code I'm getting points towards the differential pressure sensor. I'll give the thread you posted a read once I get these tail lights sorted out. This thing has got quite a few issues. Fuel pressure is dropping so I've ordered a service kit with fuel and air filter. If that doesn't fix it I'll pull the SCV and have a looksee.

 

[sir-revalot]

The differential pressure sensor should be located high up on the inside of the engine bay, on the vehicle left hand side against the guard tucked into the corner near the bonnet hinge. It's a black widget that has two rubber hoses coming from it that connect to two metal tubes that run down under the car, one to the front of the DPF and the other to the rear. The sensor itself is little more than a hall-effect sensor that detects excessive pressure in one pipe over the other. There is no electrical connection from this sensor to the DPF, it's purely exhaust pressure pushed up a (small - about 10mm diameter) pipe.

The DPF has 3 sensors on it. There are two temperature sensors and one air/fuel ratio sensor. The harness connector for the front temp sensor is white, the connector for the rear is black. I can't tell you what colour the individual wires are.

With that said, it's possible that you've got failed temp sensors (it's surprisingly common). Have a look in this thread for info on getting replacements:

https://www.navaraforum.com/threads...tops-white-smoke-and-prevent-dpf-fault.24501/

I thought pressure sensors were a variable resistor type. Hall effect sensors are primarily used for sensing motion, ie. Wheel speed sensors and cam and crank position Checked out that thread. It doesn't pertain to me as I have a functional dpf, as far as I know anyway. Hmm

 

[Old.Tony]

Think of the pressure sensor as two people blowing on each end of a straw. The sensor is in the middle of the straw. It senses motion of the pressure applied by both people, and if one person is better than the other, the motion of the sensor itself is greater.

Each end of your DPF is like those people.

As for the wires that were burned, that's not an easy one, I'll go poking at my other service manual later tonight (older model, but may still be the same harness for the same components).

 

[sir-revalot]

Think of the pressure sensor as two people blowing on each end of a straw. The sensor is in the middle of the straw. It senses motion of the pressure applied by both people, and if one person is better than the other, the motion of the sensor itself is greater.

Each end of your DPF is like those people.

As for the wires that were burned, that's not an easy one, I'll go poking at my other service manual later tonight (older model, but may still be the same harness for the same components).

Thankyou. It's much appreciated.

 

[Old.Tony]

Well that's a couple of hours I can't get back.

Neither manual has the wire colour for the exhaust gas temperature sensors. It only has the plug colours.

My car doesn't have three sensors on the DPF, only two, but there's a chance that the temp sensor wires are the same colour in your car too (why change that with a new model, just put a diff wire in for the AFR sensor).

I'll try to get under my car tomorrow, depends on how cold it is and how cooperative my joints are. We're expecting it to hit around 4-5C tonight!

 

[sir-revalot]

Thanks Tony. No need to get under there mate, it seems to be behaving apart from the p0473 code. Temp sensors and O2 sensor must be okay because there's no codes pertaining to them. It's just that dreaded differential pressure sensor that is throwing the code. I've ordered a cheapie off Ali express. I'll keep you posted. Just as a matter of interest though. Could you measure the voltage on each pin of the differential pressure sensor for me please. Key on engine off. Thanks again.

 

[Old.Tony]

I'll get that done soon, although I suspect the error isn't in relation to the differential pressure sensor - there's a separate exhaust gas pressure sensor that the manual refers to (which is NOT the differential pressure sensor) in relation to error 0473 but for the life of me I can't find the ruddy thing in the exhaust manifold. There's a pressure sensor listed ON the turbocharger but it's on the outlet of the impeller (charge air pressure, not exhaust pressure).

 

[Old.Tony]

The plug on the pressure differential sensor was reluctant but eventually obeyed when it realised I wasn't giving up.

The plug has three wires and it seems that the grey wire is ground/negative. Voltage from grey to green (middle wire) was 4.89/4.90V (it sorta flopped between those two). Voltage from grey to purple was 5.0V. Voltage between green and purple was in millivolts = ignore it.

 

[sir-revalot]

The plug on the pressure differential sensor was reluctant but eventually obeyed when it realised I wasn't giving up.

The plug has three wires and it seems that the grey wire is ground/negative. Voltage from grey to green (middle wire) was 4.89/4.90V (it sorta flopped between those two). Voltage from grey to purple was 5.0V. Voltage between green and purple was in millivolts = ignore it.

Thanks so very much Tony. It seems my suspicions are correct. There should be a ground signal. I have the 5v signal and the other two are hovering around 4.8v. Is there anything else that uses that grey wire pin out from the ecu for grounding purposes. If you have a wiring diagram I could check it out. I've ordered a manual but it's still a few days away at best. Thanks again Tony.. you're a legend.

 

[Old.Tony]

Thanks so very much Tony. It seems my suspicions are correct. There should be a ground signal. I have the 5v signal and the other two are hovering around 4.8v. Is there anything else that uses that grey wire pin out from the ecu for grounding purposes. If you have a wiring diagram I could check it out. I've ordered a manual but it's still a few days away at best. Thanks again Tony.. you're a legend.

I would love to say that the grey wire is connected to the knee bone etc, but I just don't know - I've never pulled the wiring loom apart (which is a good thing, it means my car will keep running). I would imagine that it's a ECU-supplied 'ground', so in all likelihood it's connected to the negative buss in the ECU itself, and takes its ground from the ECU ground which is right near the ECU.

It is possible - and not that much of a stretch - that your ECU is not 100% grounded properly. Nissan earthed the ECU without removing the paint from the ground point for the ECU and some cars objected to this, although they usually had errors showing up all over the place. In fact we've seen this enough that when someone complains of several seemingly unrelated errors, the first place we now point to is the ECU earth point.

Take a squiz at that? It would pay to clean it up, then once you've reattached the earth point, spray it with battery terminal sealer to ensure it doesn't corrode on you.

 

[sir-revalot]

I would love to say that the grey wire is connected to the knee bone etc, but I just don't know - I've never pulled the wiring loom apart (which is a good thing, it means my car will keep running). I would imagine that it's a ECU-supplied 'ground', so in all likelihood it's connected to the negative buss in the ECU itself, and takes its ground from the ECU ground which is right near the ECU.

It is possible - and not that much of a stretch - that your ECU is not 100% grounded properly. Nissan earthed the ECU without removing the paint from the ground point for the ECU and some cars objected to this, although they usually had errors showing up all over the place. In fact we've seen this enough that when someone complains of several seemingly unrelated errors, the first place we now point to is the ECU earth point.

Take a squiz at that? It would pay to clean it up, then once you've reattached the earth point, spray it with battery terminal sealer to ensure it doesn't corrode on you.

Thanks Tony. That was one of the first places I went to. I also cleaned the one under the air box and checked the main engine ground.

 

[sir-revalot]

Update.. so I pulled the passenger seat to open up some more wiring. Geez it's been hot under there. Carpet melted to the floor. Insulation on the loom to the rear egt sensor and o2 sensor that hard I had to sand it off with a roloc pad on a diegrinder. Opened it all up, separated yet more toasty wires. Still the dreaded p0473. So.. I thought I'd trace the grey wire from the dpf pressure sensor and do some ohm checks to see where it ended up. I found that it runs through the fuse box on the driver's side and into the ecu. It also runs in to the loom that runs to the rear egt sensor. I confirmed this by a YouTube video which showed the wiring diagram. Finally found something... this is the only two sensors that this wire runs to. So if it's connected to the ecu and all the grounds to the ecu check out then it must be an ecu fault caused by the melted wires at the dpf.. so I thought I'd try something I wouldn't usually do, I grounded out the grey wire, I figured what have I got to lose, cleared all the codes, only one and started it. Shut it down and did a full diagnostics on it... and guess what, no codes. Nothing, full pass.
Now what do I do? Do I replace the ecu at around $300 -$400 with programming or.. just ground out the grey wire. Hmmm

 

[Old.Tony]

It's possible that the solution you've found will do the job without any further issues - let's hope it's solved!