Lambda sensor - correct functionality?
Thread Starter
Audiworld Junior Member
Joined: Apr 2010
Posts: 19
Likes: 0
From: Bulgaria
Lambda sensor - correct functionality?
Hello all,
There are two fault codes in my engine ECU (Audi A6 99, 2.8Q Avant) :
16538 - Oxygen (Lambda) Sensor B2 S1: No Activity
P0154 - 35-10 - - - Intermittent
16518 - Oxygen (Lambda) Sensor B1 S1: No Activity
P0134 - 35-10 - - - Intermittent
I cleared them, but they appear again. So yesterday I’ve connect my VAG Com in graph mode and it seems that sensors work properly. Just want to note that when engine was cold in first ~2 minutes the voltage from lambda sensors was 0.450V, but as I am aware this is normal, isn’t it?
I attached the graph.
Thanks.
There are two fault codes in my engine ECU (Audi A6 99, 2.8Q Avant) :
16538 - Oxygen (Lambda) Sensor B2 S1: No Activity
P0154 - 35-10 - - - Intermittent
16518 - Oxygen (Lambda) Sensor B1 S1: No Activity
P0134 - 35-10 - - - Intermittent
I cleared them, but they appear again. So yesterday I’ve connect my VAG Com in graph mode and it seems that sensors work properly. Just want to note that when engine was cold in first ~2 minutes the voltage from lambda sensors was 0.450V, but as I am aware this is normal, isn’t it?
I attached the graph.
Thanks.
Tech Guru
Joined: Mar 2003
Posts: 6,006
Likes: 2
alas, no real ideas. I know hwo they work in theory, but have not seen enough operate r/t to comment.
I do know that until warm up the system operates rich, so that means the signal will either be hgih or low - not vary-ing.....(forget which way it is set up)
G
I do know that until warm up the system operates rich, so that means the signal will either be hgih or low - not vary-ing.....(forget which way it is set up)
G
AudiWorld Member
Joined: Nov 2005
Posts: 501
Likes: 2
How old are the oxygen sensors? The heated o2 sensors on your A6 shouldn't take two minutes to go from open loop to closed loop operation. If there were a failure of the o2 heating circuits there should be a DTC set. With VAG-COM you could check the o2 sensor heating circuit resistances to see if they are close to being out of specification.
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Tech Guru
Joined: Oct 2002
Posts: 8,009
Likes: 191
From: Olney, MD
I can't tell the horizontal scale in milliseconds/seconds, but it could well be you also have lazy sensors, i.e., they're incapable of making more rapid crossovers. Need about two/second IIRC at minimum.
Here's a short tutorial:
http://www.autodiagnosticsandpublish...or-testing.htm
Here's a short tutorial:
http://www.autodiagnosticsandpublish...or-testing.htm
Last edited by SloopJohnB@mac.com; Aug 1, 2011 at 06:12 PM.
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Thread Starter
Audiworld Junior Member
Joined: Apr 2010
Posts: 19
Likes: 0
From: Bulgaria
I can't tell the horizontal scale in milliseconds/seconds, but it could well be you also have lazy sensors, i.e., they're incapable of making more rapid crossovers. Need about two/second IIRC at minimum.
Here's a short tutorial:
http://www.autodiagnosticsandpublish...or-testing.htm
Here's a short tutorial:
http://www.autodiagnosticsandpublish...or-testing.htm
Still wondering whether O2 sensor can be a reason for rough idle, later on I will post the rpm graph, but definitely there is a problem on idling.
Thanks
Ivan
Tech Guru
Joined: Oct 2002
Posts: 8,009
Likes: 191
From: Olney, MD
LOL---now the real issue comes out.
Rough idle is almost always a vacuum leak but could be a few others. Since you only have 02 sensor codes I'd fix those first...chances are an older A6 with miles could use new sensors.
It's also possible you got a bad batch of gas or contaminated/leaded gas in Bulgaria....stuff happens.
One thing you could try if you pull the 02 sensors...take a propane or MAPP torch and heat the sensor tips cherry red for about 20 seconds, monitoring the voltage output. Should go to .9v or more. Let it cool, should drop to <.1v. If this works, it doesn't necessarily mean the sensor will work in your car, especially if it's a lazy sensor issue but it's a start. For sure, if it doesn't go to .9v+ you have a dead sensor. The heater circuits are generally continuity...if they have continuity they're ok. They actually have a resistance other than zero which would be a short.
Rough idle is almost always a vacuum leak but could be a few others. Since you only have 02 sensor codes I'd fix those first...chances are an older A6 with miles could use new sensors.
It's also possible you got a bad batch of gas or contaminated/leaded gas in Bulgaria....stuff happens.
One thing you could try if you pull the 02 sensors...take a propane or MAPP torch and heat the sensor tips cherry red for about 20 seconds, monitoring the voltage output. Should go to .9v or more. Let it cool, should drop to <.1v. If this works, it doesn't necessarily mean the sensor will work in your car, especially if it's a lazy sensor issue but it's a start. For sure, if it doesn't go to .9v+ you have a dead sensor. The heater circuits are generally continuity...if they have continuity they're ok. They actually have a resistance other than zero which would be a short.
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