Update on my DPF issue...

It basically became undrivable. Every time I stepped on the gas, the engine malfunction light would come on due to the turbo not functioning correctly and probably the engine temperature. (Interestingly enough, it would downshift and RPMs would spike when this happened. Seems to me this is putting even more stress on the engine.)

So I took it into my indie and had them replace the thermostat and water pump. Again, I mentioned this to the dealer when I had it in and they said it wasn't an issue.

After repair, they didn't have time to take it for an extended drive, and said their software didn't have the ability to issue a regen request, but told me to drive it and bring it back if issues don't resolve. After I picked it up and drove it a few blocks, the Engine Malfunction light came on the first time I gave it some gas, throwing the Turbo Underboost error code (P0299), and then a couple minutes later the DPF filter message came on (P12A7). I drove for a couple more minutes and pulled over to check codes. Both the underboost and DPF codes logged in my OBD II software. I cleared the codes and proceeded to drive again. Since no lights came back on after about 15 minutes, I took it on the Highway for about 45 minutes and no lights came back on.

Monitoring it the entire time during the drive, the engine temp was now at a steady 190-200F (was 140F before repair) and exhaust temps stayed in the 700-800F range. It seemed to be running fairly well, but I couldn't tell if it was kicking into the regen cycle. After the test drive, I pulled over and let it sit for about 20 minutes and then drove again, with no CEL or DPF lights.

Knock on anything wooden, I have had about a half dozen starts since the test drive and no check engine lights. It seems to be giving me a little more power when stepping on the gas. I am assuming that either a regen ran, even though I couldn't tell, or the exhaust was now hot enough to start purging the DPF. It probably needs to run another regen cycle or two to get back to normal, so I'm keeping my fingers crossed.

So to all that suggested the Thermostat replacement, kudos! The dealer shrugged it off and just wanted to replace the DPF filter, which would have probably had me back in for another one in less that 6 months. Again, only took it to dealer to get potential warranty work done on the NOx sensors they suggested several months earlier, only to tell me it was no longer an issue.

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'10 X5 3.5d, White and Tan
'01 X5 4.4i, Black and Tan, SOLD