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Old 10-28-2012, 05:37   #1 (permalink)
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Trouble shooting secondary air injection switch

I have found very little info online about the switch. autzone, advanced, and napa were clueless about it. I but I have figured a lot on my own.

I have a dtc p0413 secondary air incjection switch circuit low

I located the switch, and confirmed what it was at the dealer.

A ford mechanic told me the switch is supposed to have resistince of 500-800 ohms. Sounds High to me. My seconday switch tests out at 75 ohms. So the switch could be bad. But the 500-800 still seems like a really high paramater.

Further testing..... Circuit low means when the secondary switch is off, the computer wants to see that the wire coming back has 12 volts. This a ground pulsed switch, so it could be wiring, harnes, the swich its self , or something with the computer.

So heres what i did. Got my volt meter, put one meter connector on the red wire terminal, and one on a ground, turned the key on, and i have 12 volts. so that means the hot to the harness is good. Now I need to tes from the harnes back to the computer. So I used the volt meter to jump the 2 connectors in the harness to see if the computer makes a ground. I started the car and it makes the connection and i get 12v for like 5 seconds, then it drops dow to .01 volts. I reved it nothing else. So when the car first starts the computer initially makes the ground connection, but i couldnt get it to do it after that.

So I need to know what are the conditions for the computer to comand the secondary air injection switch to come on so I can re create the conditions and watch for voltage...... or I need to know what else i can do to test the computer side of this harness.


Thank you very much to those of you who read all this.
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Old 10-28-2012, 07:04   #2 (permalink)
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Re: Trouble shooting secondary air injection switch

According to this explanation:
12v Pages - The Engine - How it Works
Granted, it for Audi's but everything abides by the same laws of physics, and most of the cars pretty much use the same principles.

Your pcm may be failing it when you see the voltage drop to essentially 0. It seems to me that a resistance of 500-800 ohm would turn the solenoid into a heater, even 75 ohms seems kind of high, but I can find the specs for it, either and I can't test mine as my meter is with my van which is getting some service work right now. What year is yours? On many years, several of the solenoids are the same, you might be able to check the resistance on the others or even swap them out to see if the diagnostic moves with the switch.
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Old 10-29-2012, 06:15   #3 (permalink)
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Re: Trouble shooting secondary air injection switch

@ Catskinner

thank you for that diagram link. it has someuseful infoand gives a good picture of how everything is set up (mine is a little different but you are right same principal)

I have a 99 mustang 3.8

This solenoid is different then the rest. I tried testing the resistence of the egr control solenoid. Thats the most similar one. It has resistince of 35, half what the secondary air sol. is : 75ohms.

The egr control has half the resistence, and twice the size, of the secondary air switch.

I also tested an injector on my expedition v8 triton. It has resitence of 14.8 ohms. The inejector is very close in size to the secondary air switch. The SAI switch has 5 times the resistence of an injector.

I agree the resistence seems high on th SAI switch. Id like to know the resistence specs on yours, or if theres somewheres else i could find it that would be a huge help.

after looking at that link you sent me, it says the engine must run 20-120 seconds befre the secondary air kicks in to allow the 02 sensors to get to operating temp. So im going to retest the harness after 2 mins of running time. just to be sure.

if no voltage, i think i got a way to test the computer wire. I know the hot is good with just the key on. So ill make a jumper for the harness. Then go to the ecu find where the SAI switch wire goes in. Insert a T pin right where it goes in to the harness. Then take my volt meter put one connector on the T clip, and one connector on a good ground. Turn the key on and look for voltage on the meter.
If no voltage then it means there is a short from there back to the SAI switch harness. if there is voltage, then it means either something is wrong with the harness pin connector for the ecu..... or .... unfortuneately the ecu. Am I on spot with this diagnosing/testing technique?


thanks again to catskinner, and all those that read
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Old 10-29-2012, 06:36   #4 (permalink)
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Re: Trouble shooting secondary air injection switch

wait i got a little ahead of myself at te end of my lats post testng the white computer wire.

U say it might be showing zero volts because of the pcm. So i need to find where the SAI switch wire goes into the PCM? The PCM is what makes the pulsed ground connection, not the ecu?

thanks
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Old 10-29-2012, 14:10   #5 (permalink)
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Re: Trouble shooting secondary air injection switch

http://repairguide.autozone.com/znet...3f802404be.gif

Unless I'm mixing my stuff up (which happens), this diagram calls out the Powertrain Control Module
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Old 10-30-2012, 04:25   #6 (permalink)
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Re: Trouble shooting secondary air injection switch

I read that ECM, ECU, and PCM, are all acronyms for the same thing
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Old 10-30-2012, 15:25   #7 (permalink)
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Re: Trouble shooting secondary air injection switch

I did, too, but you had me second guessing.
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Old 10-31-2012, 05:30   #8 (permalink)
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Re: Trouble shooting secondary air injection switch

OK well now that I managed to confuse us both:) ... I have another question. Aftr looking at the wiring diagram u sent, Im wondering if the white wire of the secondary air injection switch goes strait back to the pcm, or if it goes to a relay, or junction. Guess I could trace it back, but looks like a bitc* to trace, and would be good to know anyways before I test.
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Old 10-31-2012, 16:37   #9 (permalink)
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Re: Trouble shooting secondary air injection switch

Quote:
Originally Posted by takenoprisoner View Post
OK well now that I managed to confuse us both:) ... I have another question. Aftr looking at the wiring diagram u sent, Im wondering if the white wire of the secondary air injection switch goes strait back to the pcm, or if it goes to a relay, or junction. Guess I could trace it back, but looks like a bitc* to trace, and would be good to know anyways before I test.
S154 is a splice, where that is located and how that is done is beyond me. Other than that, the diagram doesn't show anything between the pump, solenoid and the PCM. Not sure what it does at the pump, but if I were a betting man, I'd venture to say that the white wire is a ground and there's a proving switch in the pump. Bear in mind, that's a guess and I'd prove or disprove that theory by checking continuity across C152 with the engine off and running.
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Old 11-04-2012, 03:26   #10 (permalink)
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Re: Trouble shooting secondary air injection switch

Ok i fond the problem i think. the black wire with yellow tracer was broke off at the pump harness. soldered it back in and now the pump comes on and operates.

now........ about that wiring diagram. I could be all washed up, but the rectangle thing numbered 1-5 , is that a representation of the harness that plugs at the pump? because they are same colors. Itested the harness with the key on. heres my results, and what im GUESSING each wire is and does

red wire- hot - ill guess its a feed for the pump

black- went to ground. ill guess common ground for switch and pump

white with orange tracer- hot- guessing that it comes from the secondary air injection switch

white- went to ground. im guessing it goes back to pcm

black with yellow trace- went back to ground. no idea


these are just guesses. would love it if someone could tell me exactly whats going on for sure here just so i know for my own piece of mind.
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