4.4 TDV8 failed EGR EGT sensor

[Graeme]

It appears that my vehicle has a failed EGR EGT sensor, which is a common failure on these engines. A "service engine" message has appeared on start-up for quite some time, which I assumed was because the vehicle hasn't been dealer-serviced in the expected time or kms. However fault code P040D (EGR EGT temp sensor high) was found and is permanent. The resistance of the sensor, expected to be a K thermocouple, is 36.4K ohms when K thermocouples are around 1 ohm, so indeed seems to have failed and the fault description therefore assumed to be referring to the resistance. A thermocouple is just 2 wires of specific metals twisted together which generates a very small voltage when heated. Fortunately it's in an accessible spot allowing quick replacement providing its thread isn't seized, which would require removing the air intake assembly and possibly the EGR valve itself so that heat can be applied. As it's in the cooled EGR outlet pipe en-route to the inlet assembly and that the pipe looks shiny-new, I don't expect to encounter any trouble replacing the sensor.

Engine performance hasn't been notably affected although there are reports of poor fuel consumption when these fail. As its only monitoring the recycled gas temperature, I suspect it's used in controlling the EGR cooler coolant flow which may lead to slower engine warm-up in cold climates and therefore higher fuel consumption if the fall-back strategy is to fully open the EGR cooler coolant valve.

[Graeme]

The new sensor has similar internal resistance so resistance is not an indication of a failed sensor. The new sensor is now fitted and the fault has now cleared. The display message 'service vehicle' still appears so must be referring to a normal service indication, not the existence of a fault.

I removed the EGR to inlet manifold pipe to test fit a blanking plate and was rather horrified at the thick build-up of soot in the inlet manifold. Whilst the blanked EGR made 1000 rpm+ response very smooth, idle and constant throttle were grossly adversely affected by what I expect was the throttle butterfly being closed to encourage more EGR to the extent that I suspect from the wheezing noises that the turbo was being stalled or at least in danger of, so the plate was quickly removed. An EGR emulator will be fitted shortly.

[rar110]

Graeme
Do think there's any benefit in blanking the EGR on the Turbo or exhaust inlet side, and removing the coolant feed to the EGR, after fitting an emulator?

[Graeme]

I can't see much benefit in blanking the egr inlet with an emulator fitted and for me anyway not worth the effort, not that its much on the 4.4 with its valve in the V at the back of the engine.

The 4.4's egr coolant has to be kept flowing as the oil cooler is mounted on top of the egr cooler using the same flow. Blocking off the 3.6's flow might prevent any leaks in future but I wasn't moved to block the egr cooler in my TD5 D2.

[rar110]

I've had the Autocode emulator set fitted for about a week on the tdv8 3.6.

The motor is noticeably quieter. It just seems to breath better. One observable fact is no black smoke on hard acceleration. I don't really understand why the emulators would have this effect.

Also I've noticed fuel consumption drop about 1lt/100 while towing.

[Graeme]

I can't think of a reason for the engine to be quieter unless its working at lower revs and/or less throttle but the seemingly better breathing, less un-burnt fuel on wider throttle openings and better economy are pretty much what I expect. I've been remiss in not chasing-up my order for an emulator which was confirmed to be available for the 4.4.

[vk5cp]

Thanks Graeme - My 2012 4.4L TDV8 EGT sensor has just failed at 118,000 kms. Went into limp home mode as soon as load (Adelaide Hills) and high speed (100km/h) applied.

VK5CP


It appears that my vehicle has a failed EGR EGT sensor, which is a common failure on these engines. A "service engine" message has appeared on start-up for quite some time, which I assumed was because the vehicle hasn't been dealer-serviced in the expected time or kms. However fault code P040D (EGR EGT temp sensor high) was found and is permanent. The resistance of the sensor, expected to be a K thermocouple, is 36.4K ohms when K thermocouples are around 1 ohm, so indeed seems to have failed and the fault description therefore assumed to be referring to the resistance. A thermocouple is just 2 wires of specific metals twisted together which generates a very small voltage when heated. Fortunately it's in an accessible spot allowing quick replacement providing its thread isn't seized, which would require removing the air intake assembly and possibly the EGR valve itself so that heat can be applied. As it's in the cooled EGR outlet pipe en-route to the inlet assembly and that the pipe looks shiny-new, I don't expect to encounter any trouble replacing the sensor.

Engine performance hasn't been notably affected although there are reports of poor fuel consumption when these fail. As its only monitoring the recycled gas temperature, I suspect it's used in controlling the EGR cooler coolant flow which may lead to slower engine warm-up in cold climates and therefore higher fuel consumption if the fall-back strategy is to fully open the EGR cooler coolant valve.

[Graeme]

My early assumption was that the relevant sensor was the one at the EGR cooler but not long after having replaced it the fault code re-appeared when faults were queried by diagnostics, although it didn't trigger any instrument cluster fault. I have since learnt that the culprit sensor is the one in the left exhaust manifold and being the PITA to access I haven't touched it. Therefore be sure that the sensor indicated by the fault is indeed the one at the EGR cooler.
Neither of the EGR sensors can be tested by diagnostics as LR didn't provide OBD access, unlike the other exhaust sensors which can be monitored as they're required to be monitored when a DPF is fitted.

[Graeme]

Thanks Graeme - My 2012 4.4L TDV8 EGT sensor has just failed at 118,000 kms. Went into limp home mode as soon as load (Adelaide Hills) and high speed (100km/h) applied.

VK5CP
What fault code(s) are stored? Under load the EGR valve should be closed so more likely an air intake problem such as one or more of the 4 short tubes connecting the inlet duct to the inlet manifolds having split, with soot the tell-tale sign.

[vk5cp]

I use a faultmate and found the following codes

P2263
P040D
P040C
Po405

Dealer (using Testbook) beleives its EGT sensor, they will replace tomorrow (if part gets across from VK3) and we will go from there.

RR not much use if it can't get through the hills !!1 9to the remote shack

How do you find IDTool??

Chris vk5cp@arrl.net

[Graeme]

Whilst I had my Faultmate MVS re-licensed from my previous D4 to the L322, it didn't really support the engine although eventually some support was added. However for several reasons I switched to the IIDtool and GAP have been very responsive in adding facilities and general support so the Faultmate is carried as a backup code reader.

[vk5cp]

I took it to the dealer.

Ended up being a faulty EGT sensor and one of the 4 inlet joiners (little rubber joinders with a clamp on each end on the top of engine - at the back under the cover) had a 30mm tear in it (which let the air in and set off yet another sensor). Dealer replaced all 4. Its running sweet now and just about to change the rotors (120K) and pads - which is another story (see new post)