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Discussion Starter #1 (Edited)
I am trying to gain a better understanding of the readings I am seeing on my BlueDriver OBD2 scanner. I am hoping experts on this forum can shed some light on how to interpret these readings.

I read through the Diesel Emission Control System section (Page 113) in the attached PDF.

To keep this post short, I am also attaching the schematic on Pages 109-110. The temp. sensors I am enquiring about are #17, 19 and 28, highlighted with a solid red square.

My scanner reads three temperatures under the Exhaust Gas Temperature (EGT) category (see attached screenshot):
  1. Bank 1, Sensor 1 (EGT11)
  2. Bank 1, Sensor 2 (EGT12)
  3. Bank 1, Sensor 3 (EGT13)
My questions:
  1. Do sensors #19 (pre DOC), #17 (pre DPF) and #28 (pre SCR) correspond to EGT13, EGT12 and EGT11 respectively on the BlueDriver OBD2 (see exhaust gas screenshot) OR did I get them backwards?
  2. As the exhaust flows out across DOC/DPF and SCR, am I correct in assuming it gets cooler? i.e. #19 is the hottest, #28 the coolest and #17 is in between? Don't know if the DOC reactions are net endothermic or exothermic.
  3. When DPF regen happens should I see #17 exceeding 600 °C? During DPF regen should #19 and #28 also get very hot - exceed 500 °C range?
  4. Today went for a hike in the Berkeley hills . . . driving uphill to the parking lot got the sensors to exceed 600 °C (see attached sample screen shots) . . . not sure if this was a regen event OR simply due to the extra load going uphill.
  5. What are the normal values (non regen) for these sensors? ~240 °C?
  6. Scanner also reads the delta pressure across the DPF, see attached screen shot. What is the typical range for this pressure delta?
  7. Post DPF regen, logic says this delta should be less (less embedded soot, less resistance to flow) . . . not sure if this reduced delta is orders of magnitude smaller (therefore not detectable) than what DPF sees with varying load conditions - noticed, at idle, the pressure delta is less than 1 kPa, going uphill it gets close to 10 kPa (1.5 psi).
My objective here is to get a feel for these sensors (like I have for the engine coolant temperature, ECT).

Regarding ECT, as part of routine maintenance, around 90,000 miles, I changed the water pump and coolant thermostat . . . coolant temperature jumped from 82 °C to 88 °C . . . regardless of ambient temperature, coolant temperature holds tight between 87/88 °C (occasional very brief excursions to 90/91 °C) . . . except once when the ambient temp was 105+ °F and driving curvy/hilly roads, 30-40 mph . . . ECT showed 103 °C, did not throw any error codes.

To summarize - can I used these temp. sensor readings to detect a regen event?

Second, will DPF pressure delta readings tell me if the DPF is getting plugged up (regen not happening) and DPF is on its way its way out? What is the max kPa permitted before error codes are generated?

Thanks.

PS: My X5 - E70, 35d, 2011MY, June 2010 build, ~106,000+ miles
 

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Discussion Starter #2
No one? Anyone?

The truly informed ones must be busy preparing a well thought out response OR busy driving the ultimate driving machine! ;)

Kidding aside - I also sent a query to BlueDriver, they responded, apparently what gets reported on which PIDs (parameter IDs) is controlled by the vehicle . . . *generally* speaking we can assume EGT1 is pre DOC, EGT2 is pre DPF and EGT3 is pre SCR. Here is some interesting info on OBDII and its PIDs, yes these devices follow an SAE standard (J1939).

Given my ownership target is ~200,000 miles, I want to keep a close eye on some of these often reported expensive repairs - DPF/DEF/SCR, etc . . . and my hope was I can monitor DPF/DPF regen performance via these temp sensors and DPF pressure delta.

For now I will assume, at idle, after reaching normal operating conditions, pressure delta across DPF should be less than 1 kPa . . . substantially higher kPa values indicate a plugged up DPF . . . comments/thoughts?

Thanks.

PS: For those not too familiar with the X5 exhaust system, attaching this PDF I found . . . has GREAT pictures!

View this PDF in full screen mode (CTRL-L on PCs) and you can see how the two turbo chargers operate across various engine rpms as an animation . . . pretty neat . . .
 

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Discussion Starter #4
Thanks . . . yes that is the deck . . . only kept select exhaust related slides and dumped the remaining ones . . . should have included the link . . .

My mpg dropped suddenly from ~22.5 mpg to ~18 mpg . . . no obvious changes or MILs . . . yes I plan to post this . . . before posting I wanted to check out / eliminate the obvious (and yes a complete Google search) . . . once all the info is in I will start a thread asking for thoughts/likely reasons, etc . . . started to look into DPF etc as part of this effort . . .
 

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Discussion Starter #5
Monitor DPF Performance Using Generic OBD2 Reader . . .

Sharing results . . .

Initial idea was to find a simple way to monitor DPF performance using tools I already have (a generic OBD2 reader, BlueDriver) . . . and hopefully catch a deteriorating DPF before it is completely out . . . more specifically confirm DPF regen is happening and DPF is not getting plugged up.

Did a San Francisco airport run, mostly highway, round trip takes about 100 minutes. Monitored coolant temp. (steady 87/88 °C), DPF temp (mostly 250-300 °C outside of regen) and DPF pressure delta (less than 1 kPa when idling, 10+ kPa when accelerating).

Attached graph shows these values plotted against time - plotted only the section where regen occurred.

Summary:
  • A simple OBD2 reader that monitors exhaust gas temperatures can be used to record a DPF regen event. See attached graph.
  • Idling DPF pressure delta should indicate a blocked DPF - my *guess* - idling pressure delta will not be less than 1 kPa when DPF starts to plug up.
  • Running (not idling) DPF pressure delta is very dependant on the engine load, so not a good marker for DPF blockage

Some background info:
  • Always used engine coolant temp to monitor water pump/thermostat performance . . . 85+ °C is considered good enough. edycol posted a neat/easy way to test thermostat performance.
  • For DEF system performance - my approach - only replenish the passive tank AFTER the 999 message appears . . . then add 2.5 gallons of DEF to the passive tank . . . if DEF system is working properly, the system will transfer about 3 liters at a time to the Active Tank and 999 message should clear. Unfortunately my OBD2 reader cannot read DEF levels in the tanks, so have to wait for the 999 message to appear indicating a near empty Passive Tank. Here is a detailed description of my DEF service approach.
  • Battery - my approach - replace around 7 years regardless of its condition . . . possible it will last for 8+ years given I charge it regularly (twice a week), the extra year is not worth risking getting a bunch of MILs that makes no sense.
  • DPF - motivation here was to find a simple way to monitor its performance and avoid a bunch of MILs that can be misleading. DPF pressure delta of less than 1 kPa I believe is a good way to check for soot build up . . . and the exhaust gas temperature trace on a long drive should capture at least one regen event.
What I am trying to avoid is - get five different MILs, indy goes nuts, before you know it a ton of parts gets replaced . . . when all you needed was a new battery! Monitoring the devices listed above is not difficult and IMO worth the effort.
 

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