JayGee, thanks for the tip on the other thread ref the MAPT sensor reading 14.5psi when engine off. I was thinking the same thing about sensor error as that appears to be my most likely culprit. I now need to investigate the Temp bit and see how the EGR outlet temp sensor and the T bit of the MAPT sensor correlate.

In the meantime, I’ve just taken the plenum and EGR bits off again (I can do it in 10 mins now 😂) and the fluid is in there doing its thing as I write. It takes exactly one litre if you’re interested! 😉 If it does what it says on the tin, then it certainly won’t do any harm, so I’m willing to experiment with this just to see what happens as little to lose.

SpitfireS wrote:

Hello Ajmngn, I'm sorry to hear the code came back.

Browsing the web I found this image of a blocked EGR end tank cooler.
It was described as a 2011 4.4 TDV8 EGR.


If yours looks anything like that I'm thinking soaking would not do much.

Maybe you have to take the expensive plunge and have it removed.

Is it putting the car in RP mode or just throwing a fault? If it’s the latter I’d just leave it…. 2012 TDV8 Vogue (L322)

Nope, no RP. All that happens is the ECU obviously detects restricted flow, so the default setting when that happens is to shut down the EGR valve motor so the mechanical sprung valve just closes itself and no exhaust gas through into the plenum at all. It’s like a free EGR delete but without having to pay for the privilege. I just don’t want it to get worse and worse so I end up with even more problems. I say no harm in giving cleaning a go as it’s not difficult to do what I’ve described, and the fluid was only £20 for 5 litres.

You never know mate, this could be a little side hustle for me in the future and I’ll be like Bodsy but travelling round pouring fluid into EGRs and flushing them out! 😂😂 Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!

Update 3

I soaked the EGR cooler with the DPF cleaning fluid overnight Fri/Sat just gone. On Sat morn I vacuumed it all out. I then filled the EGR assembly with liquid (not aerosol) brake fluid, left for 30 mins then vacuumed that out too. Since then I’ve had two longish motorway runs and also another lengthy x-country drive today, plus plenty of shorter trips in between. I’ve totalled over 350mil since attempting the second clean. I’ve not experienced any of the described EGR shut down symptoms since. I’ve another long run tomorrow night out on a 250mil round trip. If the EGR doesn’t shut off on that trip then it’s definitely fixed and I can tell you lovely lot how you can effectively clean your EGR valve and cooler without removing them from the car! Wish me luck 🤞 Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!

Great result - hope it stays clean now. 2012 TDV8 Vogue (L322)

Update 4

Sad times. EGR valve shut down again on both the out and back legs of my 250mil round trip. So bizarre. Whatever I’ve done with the cleaning/soaking, it’s definitely helped as it seems to last longer before shutting off than it ever did before. However, it just gets to a point where the valve is fully opened for a period and then it shuts down. The throttle doesn’t seem to move but the WM says it should when EGR fully open. However, throttle definitely working as it operates fine when DPF doing regen.

Anyway, back to the drawing board I guess. 🤷‍♂️ Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!

Have a chat to these guys as an option: www.rangeroverworld.co.uk
 Gone to a good home: 2011 4.4 TDV8 Vogue SE Buckingham Blue with Ivory and clear glass = "Rory"
2025MY Defender D350 90 in Silicon Silver on coils
1974 Series 3 Lightweight = "Millie"
Many, many other Landies over the years
My preferred specialist: www.glenrands.co.uk
--------------------------------------------------

Update 5
So, the EGR valve symptom is still occurring but still only after a much longer time than before I cleaned the EGR cooler with the DPF fluid.

However, I now have a new symptom which I hope is a good thing as now have more info to potentially work out the problem 🤞

I did a 250mil towing job in the car today and I got the MIL light on the dash after about an hour on my outbound journey. I just assumed it was the P0401-00 again as that’s what’s always happened before when the engine MIL comes on. Anyway, not this time. I checked the GAP tool and it came up as ‘P245A-64 (AF) Exhaust gas recirculation cooler - bypass control circuit - Algorithm based failure - signal plausibility failure.’ It did the same on the return journey too with the same DTC, but no P0401 on either occurrence. Workshop manual is not very helpful. TOPIX is a little more so, indicating either a wiring harness issue, or a problem with the solenoid that controls the vacuum line to the EGR Cooler Bypass Valve. The bypass valve seems to be operating fine from the readings in the GAP tool and, as I’ve said further up the thread, the vacuum hose loom (which includes sensors) was changed a year ago so unlikely that.

I’m starting to think it’s now worth changing the EGR outlet temp sensor. If failing (but not yet failed) it would give false readings that would cause the issue that triggers the new DTC. It would also likely give rise to the P0401 as it would be sensing lower temps than expected in the EGR outlet when valve fully open so likely also thinking insufficient flow. The question is, is it worth dropping the c.£100 on a new temp sensor to find out?

If anyone has any ideas then I’m all ears but I’ll continue to monitor for now and see what happens. Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!

Update 6

So, after my on the drive no removal EGR cooler clean, I can report that I have not had the P0401-00 fault once. I think it’s safe to say that if the EGR cooler was indeed blocked as I’d suspected, then the DPF cleaning fluid left to soak inside the cooler overnight has done the trick.

However, as mentioned above, the new error code is the P245A-64 (AF) Exhaust gas recirculation cooler - bypass control circuit - Algorithm based failure - signal plausibility failure. The symptoms are almost exactly the same:
- EGR valve and cooler bypass valve work fine when starting up the car.
- both valves keep working normally during driving.
- once engine up to operating temp and when on a steady cruise, EGR valve will shut down in self preservation mode. Cooler bypass valve keeps working fine when on/off throttle (but suppose it would show open/closed as operated by vacuum and not ECU).
- EGR valve and cooler wake back up again during DPF regen but then go dormant after complete so back to self-preservation mode.
- clearing fault codes during driving will allow EGR valve to start working again for a while before it does same thing.
- after third occurrence, MIL shows if not cleared ECU codes.

I’m not particularly bothered by this behaviour as not harming engine; it’s like having the EGR deleted safely as still works during DPF regen. However, the pedant in me wants to fix this. Any suggestions welcome but working theories include:

- corrosion in one of plugs in harness linked to solenoid/vacuum actuator. Might explain why only happens at full temp, increasing resistance to create plausibility failure.
- issue with cooler bypass actuator a cheap part to replace but seems unlikely as current one just over 12 months old.
- issue with vacuum lines connecting solenoid to actuator. Another post on here regarding same P245A-64 code suggests vacuum lines can collapse. Seems plausible. I was supposed to have had a new vacuum harness fitted also just over 12 months ago, but worries that garage that did work just bastardised the new one for a couple of pipes and didn’t replace the whole thing.
- I’ve managed to clean cooler to restore flow through EGR but bypass valve still a bit ‘sticky’. I’m tempted to do another overnight soak as first was easy and won’t do any harm to do it again

As always, thoughts and recommendations gratefully received! Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!

Update 7

So, my P245A-64 (AF) Exhaust gas recirculation cooler - bypass control circuit - Algorithm based failure - signal plausibility failure DTC seems to have just sorted itself out.

After some serious miles in the Fatty recently heading over to Dusseldorf and back and continuing to monitor DPF and EGR values during the journey, my fault seems to have disappeared! Can’t really explain why or how as I’ve not done anything other than drive it. Where previous journeys would have the EGR shut down when cruising and engine at normal operating temperature, it’s just not happening anymore.

My best guess is that there was still some sticky oil/soot residue after my on-car clean, causing the bypass valve to stick or not open/close fully during operation. Now that everything is cleaner and the engine running sweet, maybe the oil has been burned off leaving just the soot, which is more likely to break up if drier and thus free up the moving parts that were previously not moving as they should. It’s just a theory.

Anyway, things I’ve learned as a result of this EGR DTC adventure:
- the 4.4TDV8 is actually quite a good system compared to the 3.6. It’s simple, robust and not a lot to go wrong. It’s just hard to access as under plenum and oil cooler.
- it is 100% possible to clean the cooler element on the car without removal, using the right equipment and fluids as described further up this thread. As crazy as it sounds, it’s safe to fill up the EGR with fluid to dissolve the carbon and vacuum it back out again. My car has been running fine since I did this and, despite the initial P245A-64 code, the EGR has now been fault free for about 2000 miles.

I’ll keep monitoring but I can’t see this coming back as an issue now as it’s been so long, so now I can focus some attention on some more mods instead of maintenance! Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!

Glad to hear it's behaving itself! Great technical write up for future reference too  Gone to a good home: 2011 4.4 TDV8 Vogue SE Buckingham Blue with Ivory and clear glass = "Rory"
2025MY Defender D350 90 in Silicon Silver on coils
1974 Series 3 Lightweight = "Millie"
Many, many other Landies over the years
My preferred specialist: www.glenrands.co.uk
--------------------------------------------------

Nice result Andy and a valuable addition to the collective knowledge base  2012 TDV8 Vogue (L322)