P0411 code PCM?

[Schack01]

My SES light came on and the code was P0411. checked all I could find, and then took it to a mechanic. He thinks it might be the PCM, since he
can "manually" turn on the pump, with his analyzer, but it will not come on when the car is running.
I've looked through the forums and seen a couple of ideas of where to look. I'm going to start there, before I take it to the dealer.

Any suggestions are appreciated.

2006 3.8 series II, 70K miles.

[danielsatur]

P0411 - Air induction failure
Air is added to the exhaust for better emmissions.
Are you sure, this car has an Air induction system, or is this a ghost code?
1) Disconnect the battery.
2) Discharge Control modules, by touching the pos terminal to ground.
3) Connect your battery back up, so it can reboot, and bring everything to a known state.
4) Drive, and watch for DTC's.

It could be a sensor, that enables pump at a certain temp.

[Schack01]

yes, it has an air induction system. Code has been cleared and it returns.

[tblake]

what sensor does the PCM use to determine if the pump is running? Is it the post cat O2 sensor (measuring oxygen down stream)? Find out what sensor it is and look into that before replacing the PCM.

[CrazyHorst]

Couple of things. First we must understand the motivation for using A.I.R. in the first place.

In general terms, the catalytic converter works great...as long as it is physically "warmed up". So starting from a cold condition the temp increases slowly up to a critical point where the brick "lights off" and the rate of temp increase is much much faster. In abstraction you can think of it as a sort of chain reaction but is not runaway, it is limited by the mass flow.

So really, most of the tailpipe emissions are related to cold starts. Especially hydrocarbons since every vehicle manufacturer overfuels at startup to get a reliable start.

However, enterprising minds picked up on an interesting quirk of the catalyst. Normally going "open loop" or overfueling while driving (typically in the interest of best power output, although piston protection, "hot" protection, and even the catalyst protection all require extra fuel) results in the catalyst temperature going down. The extra fuel vaporizes due to the heat but does not actually combust in the traditional sense since there's a lack of supporting oxygen for a chemically correct reaction.

Here's where the A.I.R. comes in as this supplies the supporting oxygen. That condition (with some abstraction) turns the catalyst into a sort of mini jet engine as *then* combustion is occurring with chemical correctness and a LOT MORE heat is being generated.

So back to the overfueling start and warmup to closed-loop O2 sensor control as the air-fuel ratio gradually increases. The overfueling is already necessary, simply add A.I.R. and the catalyst lights off considerably faster and lowers the tailpipe emissions.

The A.I.R. system as I recall is mostly "open loop" without much actual monitoring of flow or even catalyst temp. The coolant and air temp sensors indicate what's going on and there may be a retained timer since the last start event to layout a "plan" for how deep the PCM is going to dip into low air/fuel ratios as well as how long the A.I.R. pump is going to run.

As above, I suspect the O2 sensor is ultimately involved as well.

One last thing. To get good mixture at the exhaust ports (also aids efficient light-off) each cylinder typically has a metallic "injector" tube. However A.I.R. cannot be allowed to reverse flow as this would then be a small parallel exhaust system and the flow would cook the pump and everything else there. There are enough temperature problems with the "crosstalk" between exhaust ports due to the pulsating flow.

Bottom line is a bad/melted/stuck check valve can also impede proper flow into the system.

I also underscore the recommendation to look at other areas before you change out the PCM.

[danielsatur]

The down stream heated 02 sensors told the ECU, that the catalyst is ok.

The pre (post) heated O2 sensors are used for a feedback signal, this signal is used for the PCU control Air/Fuel mix.