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Message: An AOS does not fail, at least I've not experienced or read about one failing this way...
Changed By: MarcW
Change Date: July 14, 2011 02:01PM
An AOS does not fail, at least I've not experienced or read about one failing this way...
Change Date: July 14, 2011 02:01PM
An AOS does not fail, at least I've not experienced or read about one failing this way...
does not fail in a way that results in an engine being fed too much fuel. If the AOS affects the air fuel mixture it does by leaning it out and causing the DME to possibly reach its enrichment limit. Now there can be a curious side effect in that teh AOS leak can be a large one at idle, but at higher rpms drop off to near nothing. If the DME richens the mixture to compensate for a failing AOS and just before it reaches its enrichment threshold if the driver takes off and the engine speed increases and remains elevated the DME then will go the other way and undo its enrichment and instead of course lean the mixture out. It is possible the DME might reach its lean limit under some conditions. (I note this happened when my Boxster's oil cap was leaking. Sometimes the error codes pointed to an air leak but once in a while would point to an overly rich condition. I took this to be the MAF but it turned out to be a leaking oil filler tube cap.)
Anyhow, my info is that the O2 sensor does not fail in such a way that causes it to add a bias to its voltage output. The usual failures are the sensor stops providing readings (the sensor voltage flatlines at around 0.45V) or the sensor simply can't react fast enough to the DME's constant swinging of the air fuel mixture from overly rich to lean. I might add the swings are very tiny.
Anyhow if the O2 sensors exhibits any of the above behavior this will have the DME issuing the appropriate O2 sensor related error code(s).
I might add that the sensors must be active and working properly as determined by the DME before it will generate a P1127 error code.
My references do not even list the O2 sensor as one of the possible causes of a P1127/P1129 error. The possible causes are: MAF (incorrect signal), fuel pressure too high, fuel injector leaking, or EVAP canister purge valve open.
Since the MAF can play a role one possibly e way to eliminate the MAF is to disconnect it the wiring harness connector, clear the error codes (resets the learned fuel trims among other things) to their defaults, then drive the car normally. The car must be driven a considerable distance around 30 miles to hopefully parallel close enough a drive cycle that has the DME able to verify all systems are working and if the MAF is not the cause of the P1127/P1129 error codes to log them so you know.
Sincerely,
MarcW.
Anyhow, my info is that the O2 sensor does not fail in such a way that causes it to add a bias to its voltage output. The usual failures are the sensor stops providing readings (the sensor voltage flatlines at around 0.45V) or the sensor simply can't react fast enough to the DME's constant swinging of the air fuel mixture from overly rich to lean. I might add the swings are very tiny.
Anyhow if the O2 sensors exhibits any of the above behavior this will have the DME issuing the appropriate O2 sensor related error code(s).
I might add that the sensors must be active and working properly as determined by the DME before it will generate a P1127 error code.
My references do not even list the O2 sensor as one of the possible causes of a P1127/P1129 error. The possible causes are: MAF (incorrect signal), fuel pressure too high, fuel injector leaking, or EVAP canister purge valve open.
Since the MAF can play a role one possibly e way to eliminate the MAF is to disconnect it the wiring harness connector, clear the error codes (resets the learned fuel trims among other things) to their defaults, then drive the car normally. The car must be driven a considerable distance around 30 miles to hopefully parallel close enough a drive cycle that has the DME able to verify all systems are working and if the MAF is not the cause of the P1127/P1129 error codes to log them so you know.
Sincerely,
MarcW.
Original Message
Author: MarcWDate: July 14, 2011 02:01PM
An AOS does not fail, at least I've not experienced or read about one failing this way...
does not fail in a way that results in an engine being fed too much fuel. If the AOS affects the air fuel mixture it does by leaning it out and causing the DME to possibly reach its enrichment limit. Now there can be a curious side effect in that teh AOS leak can be a large one at idle, but at higher rpms drop off to near nothing. If the DME richens the mixture to compensate for a failing AOS and just before it reaches its enrichment threshold if the driver takes off and the engine speed increases and remains elevated the DME then will go the other way and undo its enrichment and instead of course lean the mixture out. It is possible the DME might reach its lean limit under some conditions. (I note this happened when my Boxster's oil cap was leaking. Sometimes the error codes pointed to an air leak but once in a while would point to an overly rich condition. I took this to be the MAF but it turned out to be a leaking oil filler tube cap.)
Anyhow, my info is that the O2 sensor does not fail in such a way that causes it to add a bias to its voltage output. The usual failures are the sensor stops providing readings (the sensor voltage flatlines at around 0.45V) or the sensor simply can't react fast enough to the DME's constant swinging of the air fuel mixture from overly rich to lean. I might add the swings are very tiny.
Anyhow if the O2 sensors exhibits any of the above behavior this will have the DME issuing the appropriate O2 sensor related error code(s).
I might add that the sensors must be active and working properly as determined by the DME before it will generate a P1127 error code.
My references do not even list the O2 sensor as one of the possible causes of a P1127/P1129 error. The possible causes are: MAF (incorrect signal), fuel pressure too high, fuel injector leaking, or EVAP canister purge valve open.
Since the MAF can play a role one possibly way to eliminate the MAF is to disconnect it the wiring harness connector, clear the error codes (resets the learned fuel trims among other things) to their defaults, then drive the car normally. The car must be driven a considerable distance around 30 miles to hopefully parallel close enough a drive cycle that has the DME able to verify all systems are working and if the MAF is not the cause of the P1127/P1129 error codes to log them so you know.
Sincerely,
MarcW.
Anyhow, my info is that the O2 sensor does not fail in such a way that causes it to add a bias to its voltage output. The usual failures are the sensor stops providing readings (the sensor voltage flatlines at around 0.45V) or the sensor simply can't react fast enough to the DME's constant swinging of the air fuel mixture from overly rich to lean. I might add the swings are very tiny.
Anyhow if the O2 sensors exhibits any of the above behavior this will have the DME issuing the appropriate O2 sensor related error code(s).
I might add that the sensors must be active and working properly as determined by the DME before it will generate a P1127 error code.
My references do not even list the O2 sensor as one of the possible causes of a P1127/P1129 error. The possible causes are: MAF (incorrect signal), fuel pressure too high, fuel injector leaking, or EVAP canister purge valve open.
Since the MAF can play a role one possibly way to eliminate the MAF is to disconnect it the wiring harness connector, clear the error codes (resets the learned fuel trims among other things) to their defaults, then drive the car normally. The car must be driven a considerable distance around 30 miles to hopefully parallel close enough a drive cycle that has the DME able to verify all systems are working and if the MAF is not the cause of the P1127/P1129 error codes to log them so you know.
Sincerely,
MarcW.