ECU logs certain codes, cuts boost in half

Post by **matthew1** » 25 Jan 2012, 13:51

I've noticed, now that I've lived with a P0422, that when the ECU logs a code pertaining to this* it:
a) cuts boost in half
b) when the drive cycle is complete, illuminates the Check Engine light

It's repeatable.

For instance, I can drive ten or twenty miles and see my boost hitting 9-10 PSI (normal behavior), then without warning the next stoplight I'll have only 4-5 PSI until I reset the code, CE or no CE light.

Luckily, my Autel scanner will reset codes without seeing any. It only sees them after the CE light illuminates.

*P0422... I have no idea what other codes or conditions trigger this

Post by **misha** » 26 Jan 2012, 19:17

P0422 or ECM-4801 means Three way catalytic converter(TWC)efficiency,intermittent fault/parmanent fault.

That's what my code list say.

Post by **jblackburn** » 26 Jan 2012, 19:20

Might be time for an O2 sensor spacer.

Any code related to an O2 sensor will cut boost.

http://www.ipdusa.com/products/8656/109 ... r-cel-boss

That should shut it up.

Post by **matthew1** » 27 Jan 2012, 09:32

Thanks Justin. I'll try that if it continues. Misha, yes -- it points to the cat. But I don't think it's the cat.

Backstory: I just replaced my rear O2 sensor, and continue to get a P0422. The catalytic converter does not show signs of failure, like rattling when tapped. The rear sensor replacement did double the distance I have to drive to trigger the Check Engine light.

Post by **matthew1** » 27 Jan 2012, 10:41

Justin, the heat shield already makes the stock setup tight. Any ideas on how to squeeze an additional part in there that'll add an inch or so?

I think I'd forego the special O2 socket, for starters.

http://www.o2-simulators.com/?gclid=CJW ... TAod52EQsw cheaper

Post by **jblackburn** » 27 Jan 2012, 10:46

That angle spacer thing may work too.

Post by **jblackburn** » 27 Jan 2012, 10:55

Actually, some discussion about using a generic anti-fouler (we both know how picky Volvos can be).

http://volvospeed.com/vs_forum/topic/11 ... ct-review/

Post by **matthew1** » 27 Jan 2012, 11:13

Hm. Ok, I'll get the IPD one then, and try to get in there with a big box-end wrench to tighten it, rather than buying another specialized tool. Thanks Justin.

Emissions stations around here do perform visual inspections with mirrors, so I'm hoping they won't notice it.

electech · Post by **electech** » 25 Mar 2012, 22:00

A little late, but here is some information from VADIS about your code. This is for the Mototronic computer, not sure what computer you have, but the description of the sensor functions should be identical.
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Catalytic converter diagnostic

The three-way catalytic converter (TWC) stores oxygen found in the exhaust gases and uses it to make toxic gases more environmentally friendly. The catalytic converter is a three-way catalytic converter (TWC) in which HC (hydrocarbons) and CO (carbon monoxide) are oxidized and NOX (nitrogen oxides) are reduced. As the three-way catalytic converter (TWC) ages its ability to store oxygen drops. This reduces the conversion capacity of the three-way catalytic converter (TWC). To avoid dangerous emissions the engine control module (ECM) checks three-way catalytic converter (TWC) efficiency. This check is carried out as follows.
Two heated oxygen sensors (HO2S) are used to check the catalytic converter one upstream and one downstream of the catalytic converter. The main function of the heated oxygen sensors (HO2S) is to measure the oxygen content in the exhaust gases so that the engine control module (ECM) can maintain the fuel/air mixture at around λ=1. This mixture provides optimum three-way catalytic converter (TWC) efficiency. To determine catalytic converter efficiency the amplitude of the heated oxygen sensor (HO2S) signals is compared (amplitude is a measure of signal oscillation).
When three-way catalytic converter (TWC) efficiency is good and the fuel/air mixture is normal, the front heated oxygen sensor (HO2S) signal switches between rich and lean (large amplitude) while the rear heated oxygen sensor (HO2S) signal is even (small amplitude). When three-way catalytic converter (TWC) efficiency is poor and the fuel/air mixture is normal, the rear heated oxygen sensor (HO2S) signal switches between rich and lean (large amplitude) because the exhaust gases are passing straight through the three-way catalytic converter (TWC) without being converted
If rear sensor amplitude becomes too great in relation to the front sensor signal for a number of diagnostic tests, diagnostic trouble code (DTC) EFI-443 Catalytic converter efficiency will be stored.
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As I said, this is for the Mototronic, so yours may differ slightly. As far as I can tell, all TWC codes are displayed as OBDII PO422. Other codes would be PO130-141 for the oxygen sensors.

I am not sure what to make of your slight difference with a new sensor. Hope this info on your code helps....