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Old 08-10-2009, 08:44 AM   #1
alwrxwu
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Default CPU reprogram/O2 sensor replaced question

I recently replaced my front O2 sensor but the Check Engine light still comes on after I clear it. I was told by the dealer that I need to have it reprogrammed but it'll take an hour to do it and cost me $110.

Is there any way I can do this myself? I have a Cobb Access Port, if I reprogram the MAP to stock, would this do it?

alwrxwu
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Old 08-10-2009, 10:13 AM   #2
UkNuck
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I don't think any reprogramming should be required

What code(s) caused you to replace the O2, what code(s) are you pulling now, and what mods do you have?
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Old 08-10-2009, 10:32 AM   #3
alwrxwu
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I'm getting a P0171 lean code. I orginally brought it to another dealer (while on vacation) and they told me that the front O2 sensor needed replacing. So I ordered one and replaced it myself and it's still throwing the code. My usual dealer said I need to reprogram the CPU if I replace the O2 sensor so that's why I'm brining it in since the code keeps coming back.

Mods are

Lightened pulley
Inlet pipe
Cobb Access Port

alwrxwu
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Old 08-10-2009, 10:58 AM   #4
munkis
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You should check for vacuum leaks. I bet you have one, check that inlet hose. Intake gaskets.

It could also be a bad MAF sensor.

171 = faulty 02 sensor very rarly
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Old 08-10-2009, 11:27 AM   #5
UkNuck
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Quote:
Originally Posted by alwrxwu View Post
Inlet pipe
what kind exactly? intakes can cause the P0171 code by messing with the MAF readings

P0171 CEL Thread - Everything you ever wanted to know
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Old 08-10-2009, 03:05 PM   #6
alwrxwu
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It's a Samco turbo inlet pipe.

All right, it seemed odd that the dealer kept telling me that I have to have them reprogram the CPU but I thought maybe it was to reset to factory defaults or something.

Quote:
Originally Posted by UkNuck View Post
what kind exactly? intakes can cause the P0171 code by messing with the MAF readings

P0171 CEL Thread - Everything you ever wanted to know
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Old 08-10-2009, 03:14 PM   #7
alwrxwu
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The only thing is I'm not really getting bad mileage although that's when the CEL would get thrown. It's typically when I'm cruising on the highway for a few minutes. I'll check all my hoses again.

"In his case, with the "bad" o2 sensor, the CEL would disappear after resetting the ECU, but would come back on after shutting the car off and cruising on the highway for a few minutes. When the CEL was on, the car would run extremely rich and dump fuel like crazy. I think he said he would see anywhere from 325-350 miles to a tank with conservative driving, and he was seeing something like 200-250 miles to the tank when the CEL was on."
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Old 08-12-2009, 06:39 PM   #8
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Quote:
Originally Posted by alwrxwu View Post
I recently replaced my front O2 sensor but the Check Engine light still comes on after I clear it. I was told by the dealer that I need to have it reprogrammed but it'll take an hour to do it and cost me $110.
Is there any way I can do this myself? I have a Cobb Access Port, if I reprogram the MAP to stock, would this do it?

alwrxwu
this is bull****


ya got a leak
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Old 08-12-2009, 08:40 PM   #9
Charlie-III
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Quote:
Originally Posted by Uncle Scotty View Post
this is bull****


ya got a leak
+1, there is NO need to "reprogram" the ECU because you replaced a sensor.

You can do a hard ECU reset (disconnect battery, yada yada yada...), do a reset via the AP, or just drive it to clear any "CEL's" from the bad O2 sensor (that is now replaced).

The inlet pipe should have no real bearing on how the car runs. An aftermarket intake probably would.

As others have stated, check for leaks.
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Old 08-12-2009, 08:57 PM   #10
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yeah my bad I read 'inlet pipe' as 'intake pipe' in the earlier post

one often overlooked possibility is an *exhaust* leak near the front O2 sensor - because the sensor works relative to ambient O2 if exhaust fumes get around it, the outside can look 'rich' (low O2) making the actual reading *appear* lean
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