2000 A6 Avant Intermittent P1423 Sec. Air flow too low
2nd Gear
Joined: Jul 2007
Posts: 1,430
From: Goodrich, Michigan
The combi-vlave is the one on the chart labelled "one way check valve" and is located on the back of each head. The purpose of the secondary air pump and combi-valve is to inject air into the exhaust during cold start to help fire off the pre-cat as quick as possible with the goal of reducing cold start emissions. The combi valve might also act as an EGR valve (introducing exhaust back into the intake stream for reburning), but that is not the issue here.
Which brings us to my question: how does the ECU know that only one bank has insufficient flow? There is only one flow meter on the chart, not two. This leads me to think that there are other readings, and, hence other sensors, involved and perhaps one of these sensors is at fault, like, maybe, the pre-cat O2 sensor. Or, maybe, the EGT sensor.
In any case, I would try swapping the combi-valves if they are not handed to see if the problem followed the valve. If this is not possible, I would replace the suspect valve with a new one. After that, I would replace the two sensors mentioned above. After that, the implication is a pre-cat issue.
Then again, I work on my own cars and would not be paying someone to do all this experimenting. If I were paying someone, I would dump the car and get something more reliable.
Good luck,
Bob
Which brings us to my question: how does the ECU know that only one bank has insufficient flow? There is only one flow meter on the chart, not two. This leads me to think that there are other readings, and, hence other sensors, involved and perhaps one of these sensors is at fault, like, maybe, the pre-cat O2 sensor. Or, maybe, the EGT sensor.
In any case, I would try swapping the combi-valves if they are not handed to see if the problem followed the valve. If this is not possible, I would replace the suspect valve with a new one. After that, I would replace the two sensors mentioned above. After that, the implication is a pre-cat issue.
Then again, I work on my own cars and would not be paying someone to do all this experimenting. If I were paying someone, I would dump the car and get something more reliable.
Good luck,
Bob
Last edited by bob martin; May 18, 2011 at 10:17 AM.
3rd Gear
Joined: Nov 2007
Posts: 1,980
From: Northern California
Which one is the "combi valve"? I have this same problem on my wifes 2000 A5 Avant. Constant DTC 1423
I replaced all the vacuum hoses on the top of the engine and the passenger side "vacuum value" because I broke a nozzle trying to get the dry rotted hoses off, and that stopped the DTC 1423 for about 7 months, then it came back again, the one long one on the passenger side still needs changing.
Can you point out in the diagram which one is the "combi valve" is that the same thing as the ERG valve?
Her tag is due next month and I need to fix this so I can get emissions to pass so I can get a tag.
I replaced all the vacuum hoses on the top of the engine and the passenger side "vacuum value" because I broke a nozzle trying to get the dry rotted hoses off, and that stopped the DTC 1423 for about 7 months, then it came back again, the one long one on the passenger side still needs changing.
Can you point out in the diagram which one is the "combi valve" is that the same thing as the ERG valve?
Her tag is due next month and I need to fix this so I can get emissions to pass so I can get a tag.
1st Gear
Joined: May 2011
Posts: 2
I would LOVE to get rid of this POS, but it is paid for, and it is much cheaper to chase down these problems than replace the car with another car the same size. There aren't many options that aren't mini-vans as replacements for the Avant.
This thing has been an electrical nightmare, and I have been battling this DTC 1423 issue for 5 years now. I fix it just long enough to get emissions done, and then the light comes back on until I fix it the next year, the stealer-ships want Min $1000 to even look at anything to do with the secondary air injector codes.
It is a mechanically sound vehicle, but it is expensive to fix these re-occurring problems like this. I can't recommend an Audi to anyone now because of the last 10 years we have owned this 2000 A6 Avant.
This thing has been an electrical nightmare, and I have been battling this DTC 1423 issue for 5 years now. I fix it just long enough to get emissions done, and then the light comes back on until I fix it the next year, the stealer-ships want Min $1000 to even look at anything to do with the secondary air injector codes.
It is a mechanically sound vehicle, but it is expensive to fix these re-occurring problems like this. I can't recommend an Audi to anyone now because of the last 10 years we have owned this 2000 A6 Avant.
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Kenny Benike
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