P0171/P0174 just went away?

[mhoehn]

All, I'm enjoying my X5, in month 3. I'm new to X5, but have had BMWs for years. Did my research, and bought an '03 with 140k and the 3.0L. it had the P0171/P0174 issue when i bought it, quickly found a crack in the throttle body boot and replaced it. but still had the codes coming back.
So I ordered the CCV "kit". but before I could install it, and after 6-8 weeks of driving since we bought it, the codes went away. i haven't seen one for 2-3 weeks. Truck has always ran perfect. no stumbles at idle, no smoke, nothing. runs like a new truck. no leaks, no smoke.
now, after 2 weeks with no codes, I get the warning to check the low engine oil. I've read all the stories about the bad CCV system "sucking" the oil out of the pan. YIKES! the truck was 2 quarts low. I bought it from the dealer with a fresh oil change, and now we've driven 2500 miles.
does it make sense that the P0171/P0174 codes just "went away"? is this related to low oil? do i need to spend my 3-day weekend putting in the new CCV parts and hoses?

[upallnight]

Since you already brought the CCV repair kit, just install it and you won't have to worry about it come next winter.

[sunny5280]

Originally Posted by mhoehn

All, I'm enjoying my X5, in month 3. I'm new to X5, but have had BMWs for years. Did my research, and bought an '03 with 140k and the 3.0L. it had the P0171/P0174 issue when i bought it, quickly found a crack in the throttle body boot and replaced it. but still had the codes coming back.
So I ordered the CCV "kit". but before I could install it, and after 6-8 weeks of driving since we bought it, the codes went away. i haven't seen one for 2-3 weeks. Truck has always ran perfect. no stumbles at idle, no smoke, nothing. runs like a new truck. no leaks, no smoke.
now, after 2 weeks with no codes, I get the warning to check the low engine oil. I've read all the stories about the bad CCV system "sucking" the oil out of the pan. YIKES! the truck was 2 quarts low. I bought it from the dealer with a fresh oil change, and now we've driven 2500 miles.
does it make sense that the P0171/P0174 codes just "went away"? is this related to low oil? do i need to spend my 3-day weekend putting in the new CCV parts and hoses?

Yes, this makes plenty of sense as it is performing exactly as designed. Here's a high level summary of how the system works:

The computer monitors various systems and when one of the monitored systems falls outside of specification it illuminates the Check Engine Light (CEL). Even though the CEL is illuminated the computer continues to monitor the systems. If it determines a parameter that was once out of specification has fallen back into specification it will extinguish the CEL. However the code which caused the CEL to be illuminated will be stored in memory.

The computer works on "drive cycles". I can't say specifically what constitutes a drive cycle but it is something along the lines of a start, drive, stop sequence. In order for the CEL to be illuminated a monitored parameter must be out of specification for a number of drive cycles. Typically two. The same applies to extinguishing the CEL. However the exact number is specific to the monitored system / parameter.

By having corrected the problem which caused the CEL to illuminate the parameter which was out of specification fell back into specification. The computer observed this and extinguished the CEL after the appropriate number of drive cycles. The retained code(s) will eventually be purged after a number of drive cycles. In my research I learned 40, 80, and 120 drive cycles were the typical numbers. Again tied to the specific issue.

In the end the system did exactly what it was designed to do. I wouldn't worry about it. The crack in the boot is likely to have been the cause for these error codes.