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-   -   Secondary Air P0411 Help Needed (https://www.taurusclub.com/forum/87-engine-drivetrain/120827-secondary-air-p0411-help-needed.html)

OldWagon 03-26-2007 09:19 AM

This is for a Northeast 98 Vulcan with the wonderful secondary AIR system normally shoehorned only into California cars, but as I understand it, was fitted to certain NE cars.

I'm once again getting a P0411 code ("the flow in the secondary air injection system is incorrect") on hot idle.

Relevant diagnostics words from the Ford Manual:
"The functional check may be done in two parts: at startup when the AIR pump is normally commanded on, or during a hot idle if the startup test was not able to be performed. The flow test relies upon the HO2S to detect the presence of additional air in the exhaust when introduced by the Secondary Air Injection system.

The DTC associated with this test is DTC P0411. "

Air flows into the manifold on cold startup so the pump and valve seem to be OK.

The code appears after driving about 20-30 minutes while idling at a traffic light or stop sign -- gotta be the "hot idle" referenced in the manual.

My question is what or where is the "H02S" ?

(I've done a search, but everyone here who uses this acronym apparently knows what it is...)

godspunk32 03-26-2007 09:24 AM

HO2S = Heated Oxygen Sensor.

All of the oxygen sensors in teh Taurus have a heated wire that brings the temperature of the sensor up quicker than if they were just stuck in the exhaust pipe, thus bringing the car out of closed loop more quickly.

JR




OldWagon 03-26-2007 09:24 AM

Quote:


My question is what or where is the "H02S" ?

[/b]
Nemmine - found it in the manual : heated oxygen sensors.

Any easy test for the sensors? Manual has something that I don't understand about switching and output voltage...

godspunk32 03-26-2007 09:41 AM

The only way is to either use a breakout box, which is a specialty tool, and something only the dealer would have, or to measure the voltages and resistance coming from the sensors.

JR




shoz123 03-27-2007 10:34 AM

DTC Description Possible Causes Diagnostic Aides
P1411 - Secondary Air Injection (AIR) system downstream flow The secondary air injection system does not detect the presence of air in the exhaust when introduced by the secondary air injection system Electric AIR Pump
Hose from AIR pump leak
AIR bypass solenoid leak/blocked
Hose from AIR pump blocked
AIR bypass solenoid stuck open/closed
In order to test the AIR pump, it must be capable of driving the HO2S lean.


There is nothing wrong with the HO2s. It is the SAI that is bad and usually it is the relay located under the pump. It is located on the subframe under the battery. There is a small 1" hose that appears to go nowhere, this is the intake hose for the pump.

OldWagon 03-27-2007 10:48 AM

Quote:

There is nothing wrong with the HO2s. It is the SAI that is bad and usually it is the relay located under the pump. [/b]
That's the odd thing. I get air through the injector pipe when starting up, cold. It quits after a minute or so, so I think the pump, relay, and bypass solenoid are working, at least when cold.

The pipe from the pump to the solenoid seems to be ok.

Any idea where the pump intake is? Maybe a screen is partly clogged and I'm not getting the air flow I need.

I guess I could try cycling the solenoid (is it 5v, or 12v or something else?) when it's hot... maybe it expands and jams.

shoz123 03-27-2007 11:00 AM


OldWagon 03-27-2007 11:16 AM

Quote:

Here is more info

[/b]
Thanks for the link. I just visually checked the system and discovered what must be the intake tube (short 90 degree rubber elbow pointing down) with its nose buried against/into an oil or transmission line.

It was at least 3/4 blocked by the oil line. I managed to twist it forward so its little snout is now clear. If this pump depends on free breathing, it was definitely not getting free air flow.

I have one more thing to check, then I'll reset the codes and drive around for a while.

Thanks,
Dave

shoz123 03-27-2007 12:20 PM

FWIW the PCM will see if the H20s go lean when the SAI should be running when the engine is first started. If not the PCM will try again when at a highway cruising speed. It is then when it will set a code if the sensors don't go lean.

OldWagon 03-27-2007 01:22 PM

Quote:

PCM will try again when at a highway cruising speed. It is then when it will set a code if the sensors don't go lean.
[/b]
In my case, my experience matches the description in my Ford manual -- the code light came on Sunday after a slight stumble while idling hot at a traffic light (see my OP -- the first time it came on was idling at a stop sign, waiting for our endless Northeast traffic to clear).

Anyhow, I should be able to do my next, full visual on the pipe between the solenoid and the exhaust manifold with mirror tomorrow. Right now, the car's at my wife's work right now and won't be back until after dark. Tomorrow morning, after the visual, I'll reset the code by taking off the negative terminal, then (terminal back on) drive around a couple of days to see if the SES light reappers.

Thanks, Shoz123, for all the pointers.

Dave


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