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Old 05-15-2003, 03:36 PM
Arthur Dalton Arthur Dalton is offline
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,768
Here is a little info for DIYers and "Z-Techs" ..
If you are wondering about that one , he is the guy at a Dealer that is just leaning and when you go in there for a minor, not too technical of a complaint, the Service Manager says ' Hey , give this one to one of the Z-Techs !!!! .....[ "A" being a seasoned tech, and z being..well, you know..]
Heard that one yesterday from a friend who works at the local Suburu Dealership..

Anyway , I guess any DIYer with the curiosity to go a little further
using this Forum could be called a Z Tech, without anybody hurting any feelings..

You fix anything by knowing a little about it .. then your brain surprises you and says , " hey , if this is supposed to do that and this is disconnected from them, then it can't do this ...etc..etc
What was once a very complicated problem now becomes very simple and you become very Smart...[sometimes]
So, back to AIR systems and what the hell are they/do they do/ how the hell do I fix one ??????

AIR system consist of a pump, [some belt driven, some electric] , that pumps some outside air into the exhausting air of the motor at first cold starts to help in controlling emmission. This air gets the CAT up to temp faster than w/out a pump.
The parts involved to do this are the pump, a hose with a valve between the pump and engine, and a check valve at the engine
side of the hose.
The ECU sends an elecrical signal to the pump to turn it on.
At the same time , this very same elecrical signal goes to the SWITCH-OVER-VALVE.

[A little on SOV's]--any sov [ and there are a few in your car]
is simply a valve that allows engine vacuum to flow through it when its little coil is electrically energized]

So, now we have the pump running, the sov being energized and allowing vac to open the control valve in the pump hose ,allowing air to get to the engine to do its job heating the cat and cutting emmissions.
The last little piece in the system is a check valve [mechanical] at the engine [ so gas pressure can't go back into the pump]
So, if we get an AIR code , something is not working..
First stop is to look see if maybe a vac line is off at the control valve or the SOV. No vac=no AIR. Or maybe the pump is just not getting a signal from the ECU, or maybe---well you get the idea..

Now, how does that CE lamp know something is afoul...
Simple... it does a little test that looks at the signal from the O2 sensor ...when the pump system is working correctly, it makes the exhaust very lean and the o2 sensor verifies this for the ECU..if it does not , it pops a Code and you go NuTS !!!

As SB pointed out in a recent "Scope Patterns" lesson,
a bad o2 sensor can be at fault if it does not have the capacity to READ this very lean condition..

So , when one ask for a remedy of an AIR code , I say the best bet is to know a little about the basic workings and then you can use your diagnostic abilities [ and we all have them] much better than you think...
These little ' How it Works " post are just "Basics" and intended to help those new to the different problems one runs across and hopefully to get some benefit from ....
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