temperature dependent O2 sensor
09-17-2015, 04:05 PM
#11
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" NOt to be rude, but sometimes you just have to take it to a competent audi technician"
Yes, but that will be my last resort. The nearest dealers (3 of them) are all 90 miles away, and there are no independent techs either.
Yes, but that will be my last resort. The nearest dealers (3 of them) are all 90 miles away, and there are no independent techs either.
09-17-2015, 05:43 PM
#12
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Defective 02 sensor?
here's one source for testing 02 sensors. It sounds like you're either getting a too rich signal from the 02 causing the lambda to go to minimum. Just a SWAG.
O2 Sensor FAQ
Unfortunately, if the tests show the 02 to be good, you might have a bad engine control module. That's where the dealer comes in…they can swap in a new one at THEIR risk and if it doesn't fix the problem it's part of their 'diagnostic fee.'
09-22-2015, 07:50 AM
#13
Just a hunch that your Bank 2 MAF sensor might be bad, since the problem hits after it goes to closed loop. Can you swap MAF sensors side to side? If the codes swap sides, time for a new MAF.
If your missing symptoms can't be felt,(just measured by VCDS), eg no bad hesitations, my hunch could be wrong, since when my MAF failed the hesitations were severe and car was barely drivable.
If your missing symptoms can't be felt,(just measured by VCDS), eg no bad hesitations, my hunch could be wrong, since when my MAF failed the hesitations were severe and car was barely drivable.
09-23-2015, 07:42 AM
#14
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Just a hunch that your Bank 2 MAF sensor might be bad, since the problem hits after it goes to closed loop. Can you swap MAF sensors side to side? If the codes swap sides, time for a new MAF.
If your missing symptoms can't be felt,(just measured by VCDS), eg no bad hesitations, my hunch could be wrong, since when my MAF failed the hesitations were severe and car was barely drivable.
If your missing symptoms can't be felt,(just measured by VCDS), eg no bad hesitations, my hunch could be wrong, since when my MAF failed the hesitations were severe and car was barely drivable.
Only 1 MAF.
09-23-2015, 02:49 PM
#15
Doesn't the 4.2 have 2 MAF sensors? My wife's 4.2 Touareg has 2, so I figured all 4.2's have 2.
My 2.7 A6 has only one and it failed at about 200k miles with codes and severe hesitation and lurching. Perhaps with 2 on a 4.2, a failure of one will not be as drastic.
My 2.7 A6 has only one and it failed at about 200k miles with codes and severe hesitation and lurching. Perhaps with 2 on a 4.2, a failure of one will not be as drastic.
09-24-2015, 08:57 AM
#16
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09-25-2015, 01:38 PM
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are the O2 sensors after the catalytic converters used in the closed loop fuel control, or are they only used to sense the health of the converters?
I'm wondering if the exhaust leak between the converter and the sensor two is the issue.
I'm wondering if the exhaust leak between the converter and the sensor two is the issue.
12-30-2017, 07:56 AM
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intake manifold air leak causes fuel trim to error out at idle
2000 A6 4.2, 115000 miles. Problem is with bank 2 sensor 1 intermittent. I assume it is a wiring issue, but i can't find it. I'm reluctant to probe the engine controller connector, i have seen the contacts damaged from careless probing.
I had a code for intermittent sensor, so i replaced the sensor with the Bosch OEM part.
Now i get P0154 code after the coolant temperature gets near 90C.
Watching the lambda values with the Ross-Tech tool, bank 1 ramps between ~0% and -5%. Bank 2 ramps between ~0% and +5%. When the coolant temperature gets near 90C, bank 2 sensor 1 goes to +25% and the voltage to ~50 mV.
i cleaned the connectors.
No amount of pulling, pushing, or bending on the wire harness or connectors will make the sensor fail at low temperature or work after it has been hot. Letting the car cool overnight starts the process all over. The sensor wire is not near the exhaust pipe
I recently had the transmission out and i have a leak in the exhaust at the resonator, which i was hoping to hold off replacing until next summer.
i did find the passenger side (US drive) intake manifold flap stuck and fixed that.
No codes indicating air leaks.
If i drive it until it is hot, i get codes for misfire on 5, 6, 7, and 8, and rough running.
No other codes.
i assume it is wiring, the harness passes behind the coolant expansion tank, but i'm not having success tracking it down.
I had a code for intermittent sensor, so i replaced the sensor with the Bosch OEM part.
Now i get P0154 code after the coolant temperature gets near 90C.
Watching the lambda values with the Ross-Tech tool, bank 1 ramps between ~0% and -5%. Bank 2 ramps between ~0% and +5%. When the coolant temperature gets near 90C, bank 2 sensor 1 goes to +25% and the voltage to ~50 mV.
i cleaned the connectors.
No amount of pulling, pushing, or bending on the wire harness or connectors will make the sensor fail at low temperature or work after it has been hot. Letting the car cool overnight starts the process all over. The sensor wire is not near the exhaust pipe
I recently had the transmission out and i have a leak in the exhaust at the resonator, which i was hoping to hold off replacing until next summer.
i did find the passenger side (US drive) intake manifold flap stuck and fixed that.
No codes indicating air leaks.
If i drive it until it is hot, i get codes for misfire on 5, 6, 7, and 8, and rough running.
No other codes.
i assume it is wiring, the harness passes behind the coolant expansion tank, but i'm not having success tracking it down.
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