XC70: Engine D5 DPF Exhaust Temperature Sensor Replacement

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DPF Temp Sensor Replacement Guide

Having had the pleasure of struggling with this “Easy” job, I thought I would pull together a bit of a guide.

So…a real common problem on D5 Volvos from around 2008 to 2012 relates to the DPF temperature sensor going open circuit. Apparently caused by a bad batch of sensors (from Delphi), it causes intermittent power loss (particularly up hills) as the car puts the engine into limp mode, but it won’t put the EML on. It will log a fault though - P2452(02) or P245202 which is Diesel particulate filter (DPF) pressure sensor A - circuit malfunction.

So, this should be relatively straight forward…but the forums and VIDA were not amazingly helpful…so wanted to outline what I encountered and share some information to help others.

First things first, you need to understand how the DPF system is set-up. This is all based on my 2010 Volvo XC70 with the 205bhp twin turbo D5 engine (but I believe the DPF system is similar on all models – in fact, the temp sensors and the DPF itself seem to fit multiple models). The DPF sits between the Catalytic Converter and the Exhaust. The below image is the Cat and the DPF and the second image shows the exhaust (the DPF connect onto 9 in the image).





The System has 3 sensors – two located in the Catalytic Converter and one in the DPF. The DPF also has two pressure pipes that go off to the DPF pressure sensor.



- Red Component is the DPF temp sensor

- Green Component is a small T27 torx screw that must be removed to allow access.

- Royal Blue Component is the wiring connector – this is clipped to the loom and slides out for easy access.

- Light Blue Component is the hose connectors for the DPF Pressure sensor. You do not need to touch these if following method 1. These will either be push fit or will have jubilees on them. Either way, suggest re-fitting with Jubilees if removing.

So…these 3 sensors. There is a traditional Lambda sensor in the CAT, as well as a temp sensor. There is also another temp sensor in the DPF (the two temp sensors are identical, but the DPF one is cranked to one side). The reason why I am sharing this detail is it seems many people misdiagnose the one on the CAT as causing these issues, but it’s almost always the DPF one that fails. Again, any old OBD reader or VIDA can confirm which one is affected. The temp sensor in the CAT is the front temp sensors and the temp sensor in the DPF is the rear sensor. If you check the live DPF temp sensor feed, it should read between 200 and 300C when the car is running. If it is static at 335C or 999C (or similar), it is faulty. The car chucks a stock figure in if it doesn’t get a proper reading).

You will need to confirm part numbers using VIDA for your vehicle, but for the 2010 XC70 with D5 engine, the rear DPF temp sensor part number is 31431047. Apparently, Delphi originally supplied the part to Ford/Volvo, and there are tonnes of carbon copies kicking about under a dozen or so brands (but all most likely out of the same factory). There is a slightly different design version a few manufacturers supply that has a different sensor head – noting issues with the original, I decided to try this style (but I have heard the quality issues were resolved so probably a safe bet to buy from Volvo). It’s about £95 from Volvo or £50-60 for a decent named equivalent from Delphi, Febi etc.

It looks like this:

Old DPF Sensor Image



New Aftermarket Sensor Image



So on to changing it…now there are two methods. Method 1 which is changing the sensor in situ and Method 2 which involves removing the DPF filter to give better access. Method 1 should be easy…but if I am honest, I wish I went with Method 2 as it would have been a lot quicker for me.

Method 1 – In Situ Replacement

Jack up car and support on axles stands. I use a rubber pad on the factory cill jacking points and then support under the car at the noted points within the user manual using axles stands and a piece of wood on top.

Try to get the car high enough so the wheels are a few inches off the ground.

Remove cross member from across the car – two 13mm bolts either side and it just slides right out (see below):



Access is best from the passenger side (UK) - you will be met by this sight…





Undo the Torx27 screw shown in green above. This is a bit fiddle as its facing away from you – don’t lose the bolt or hose connector.

Slide the wiring loom out of the holder and disconnect (Blue).

Cut off the old wiring connector – you can now thread a 17mm ring spanner up and on to the sensor (Red). It is extremely tight and you will need to pull the DPF down and across with your spare hand to improve access (it is quite flexible). I STRONGLY suggest that you have a set of flex headed ratchet spanners before starting this job – it is almost impossible without them if you need to clean up the threads (at least on the XC70 AWD – you may get more access on FWD cars).

Undo the 17mm sensor. It will be REALLY tight. On mine, it took me a few hours to get it off, working it a couple mm’s at a time. I soaked the sensor in Plus Gas penetrating oil a few times and left to sit. Some may come out easy, but I suspect if it’s original, you will have a battle. I used a standard 17mm ring spanner and then had to use another spanner on the bottom as extra leverage (having onto about an inch of travel).

Once the sensor is out, you can fit the new one. If you had a massive battle the old sensor out, you may wish to test the threads first with a M14 x 1.5mm bolt (or get the old sensor bolt off be removing the wiring and use this). My thread was absolutely goosed and I should not monkey a new bolt into it (it was just stripping threads).

If you have the same issue, don’t worry – there is a solution…a thread chaser. It is a bit like a tap, but a lot less aggressive and will follow the original threads. A great tool…but unfortunately most of the market is saturated in cheap rubbish these days.

You need to purchase an M14 x 1.5mm thread chaser. The only problem is 99% of the ones on Amazon are cheap Chinese steel tools that will not touch the exhaust that has been through thousands of heat cycles. I tried two cheap ones, plus a Sealey branded one – they all had their threads stripped.



The solution is simple and cheap…Snap-On sell a lovely set for about £160 under their Blue Point brand. A bit pricey for one job…but they also sell single components as well. You need to buy part TRT14150 - M14 x 1.5 Metric Rethreading Tap (Blue-Point®). I bought this from the UK Snap-On website for £4.86 inc!! Bargain!! Postage was £6.99, but for the job it did, I suggest anyone attempting this repair buys one as a matter of course. They are made by Lang tools in the US and I really rate it.



Now as I mentioned, I had already stripped 3 re-threading tools due to how hard the exhaust was. No issues with the Snap-on one through. I repeat, you do need a flex-head ratcheting spanner (16mm for the thread chaser) and basically, you start to thread it into the sensor hole manually, and then you slowly tighten it (adding lubricant every couple turns). If it gets tight, back it out a few turns and then repeat tightening until it bottoms out. This tool completely repaired the threads for my sensor and made it possible to hand screw the new sensor all the way in. I presume it’s a combination of rust, soot and all the heat cycles that welds the sensor in – this all then gets disturbed when you remove it.

Once the threads are repaired (if needed), fit the new sensor. The wiring needs to point towards the front of the car and the sensor is keyed so need to drop in that way. This is actually a little tricky, I had to pull the DPF down quite a bit to get enough access (but it probably isn’t an issue on FWD). The sensor will then drop into place and you can start to tighten the bolt (by hand and then with an open 17mm wrench). Keep tightening until you cannot anymore – I think its 45nm, but you cannot check that on the car so just tight enough. Note – the sensor nut sit’s a little proud…if the sensor no longer moves up and down, it’s all sealed up.

You can now refit the T27 bolt, re-connect the wiring and slide it back onto the plug holder.

Re-fit the cross member (13mm – tightened to 24NM) and drop car back to the ground.

Method 2 – DPF Removal (sorry less pics – I struggled on with method 1, but in hindsight method 2 would have saved me hours!).


Jack up car and support on axles stands. I use a rubber pad on the factory cill jacking points and then support under the car at the noted points within the user manual using axles stands and a piece of wood on top.

Try to get the car high enough so the wheels are a few inches off the ground.

Remove cross member from across the car – two 13mm bolts either side and it just slides right out (see method 1).

Undo the Torx27 screw shown in green above. This is a bit fiddle as its facing away from you – don’t lose the bolt or hose connector (see method 1).

Slide the wiring loom out of the holder and disconnect (Blue) (see method 1).

Undo the two 12mm bolts holding the DPF to the intermediate exhaust section. These will be tight and rusty – ideally, loads of penetrating fluid and heat! And maybe even Irwin bolt grips if you have trouble. Worst case, buzz them off with the angle grinder or Dremel.

Undo the two 13mm bolts that hold the DPF hangar brackets.

You will now be able to manoeuvre the DPF to improve access to the three 12mm bolts connecting it to the flexi pipe from the Cat. These are probs rusty and tight as well…heat/penetrating fluid/bolt grip sockets or cut them off if all else fails. You will want to support the DPF somehow as you undo these.

Once free, you can get access to the two vacuum pipes (pictured above). These will either pull right off or may have jubilee connectors. Be gentle, I have heard stories of the pipes or sensors falling apart.

The DPF is now free. Take into your nice warm garage, cut off the wiring and get lot’s of heat/penetrating fluid on the sensor boss. Get a 17mm deep socket, insert over the sensor (or buzz the sensor bit off if needed with a grinder), and untighten. If it’s cherry red hot, it will probably come out easily. Use breaker bar if needed (a luxury you don’t have under the car for method 1).

If the sensor came our easily, re-fit the new one. If you have any issues with the sensor hole threads or you can’t screw the new sensor bolt in by hand, refer to method one and use the Snap-On thread chaser to clean it up. DO NOT BE TEMPTED BY ANY CHEAP VERSIONS ON AMAZON If that doesn’t work, you will need to tap it (M14 x 1.5) or look into a helicoil type repair.

Once threads OK, the new sensor can be screwed in. It is keyed and needs to have the wiring pointing slightly to the left of the top flange bolt. Once in, you can re-fit the cable holder bracket and re-fit to the car. Use quality M8 stainless nuts / washers to replace the ones you took off.

EXTRA STEP – If you had to cut the exhaust bolts at either side (DPF to Cat flange or Exhaust to DPF flange), you will need to get the old exhaust bolts out. These are bolts, not studs…but they are splined and pressed into place. I have seen a few methods to do this…

- You can cut a slit in the flange to release pressure and hammer out, but I think that’s a bit rough.

- You can heat it up until cherry red and hammer out. There is a huge chance you will bend the flange though.

- You can press it out using a clamp and socket…but that didn’t work for me.

- The easiest and proper way is to grind the back of the bolt head off using a mini grinder. Wear eye protection! Be careful, you just want it flush. Then punch the centre of the bolt (you will be able to see the outline) and drill out using a cobalt bit. I did a little 4mm pilot and then went straight to 7.5mm. You only have to drill 10mm tops and then the studs will push right out (or push an 8mm bit through if any issues). You can then thread a new m8x50mm bolt with washer both sides and add a flanged nut on the other side.

Once DPF back in position, refit pressure hoses and secure with jubilee clips.

You can now refit the T27 bolt (if you haven’t already), re-connect the wiring and slide it back onto the plug holder.

Re-fit the cross member (13mm – tightened to 24NM) and drop car back to the ground.

Happy days – enjoy a nice cold one!

Hopefully this is useful…I found a few bits about this, but this is a nice easy to follow guide. I wish I did method 2 in hindsight. But if I had flex headed ratchet spanners and the Snap-On tool day one, this would have been a 2-3 hour repair (most of the time spent getting old sensor out). If you don’t break any exhaust or flange bolts, then I reckon you could drop the DPF and do it that way in a similar time. Add 20 mins per flange bolt you need to drill out.

Cheers,

Rob