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Discussion Starter · #1 ·
I have a 2008 Trailbalzer LT, which I installed a new K and N air intake on, as well as a throttle body spacer. My check engine light came on and gave me the code P0418, which says secondary air injector relay malfunction. I went to Advance auto and got a new relay, but that did not turn the light off. I pulled the fuse to reset the computer but the light came on a few hours later again. Can someone help me with potential fixes?
 

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Install the original air filter unit and throw the K&N system away. They cause a lot of troubles on all the vehicle they are installed upon.

If a new relay “A” doesn't solve your problem, prepare to perform resistance, continuity, and ground integrity checks on all associated wiring, but be sure to disconnect the SAI wiring from the PCM to prevent damaging the controller during resistance tests.

Take seriously good notes - this can be a cost-driven factor to repair and you need good info to stay out of selling your dog or sister or body parts to pay for what's next.

Compare all obtained readings with the values stated in the manual, and make repairs or replace wiring as required to ensure that all electrical values fall within the ranges specified by the manufacturer.

NOTE:
Pay particular attention to the SAI pump’s internal resistance, and replace the pump if this value does not agree with the specified value, very closely.

At this point, it is good idea to apply pure DC --- [not-from-a-battery-charger which is only Half Wave rectified and will screw up your readings!] --- current to the pump directly (as per the instructions in the shop manual) from the battery with an ampere gauge incorporated into the jump wires to measure the pump’s current draw.

Why an Ampere reading?
Because if it's drawing too much current (ie: frozen motor, frozen water in the motor, seized bearings in the motor - etc) - it can pull the "A" circuit Voltage low - and the computer sees that as an "A"-circuit failure and pops the SES or CEL.​

Compare this tested value you get - and which you WROTE DOWN - RIGHT? --- with the value stated in the manual, and replace the pump if its observed current draw exceeds the stated value by +/- a few percent.

Note that if there are no short circuits in the circuit, an excessive current draw indicates an incipient failure of the pump motor.

You can use this tested value as an "observed result drawing to a decently thought out conclusion" without it being too much of a crapshoot.

Just don't spill any water on a witch or your odds go 'way down.

BTW: Bad-frozen-seized, high Amps drawing motors will destroy relays.
 

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2004 chevy trailblazer_ls
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Check for water in the hoses (where they go into the pump, below the drivers seat, under the car). There's a relay, and wiring harness, check that, too. And also the valve just above the exhaust manifold.
I'm thinking you'll find poor connections.
 

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Discussion Starter · #4 ·
Check for water in the hoses (where they go into the pump, below the drivers seat, under the car). There's a relay, and wiring harness, check that, too. And also the valve just above the exhaust manifold.
I'm thinking you'll find poor connections.
So far so good, I did all that plus I slightly bent all the pins on each connection to hopefully make it a little tighter of a connection and the light went off. Thanks!
 

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I am so glad I don't have that air injection system. It seems somewhat troublesome.
 

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Discussion Starter · #6 ·
I am so glad I don't have that air injection system. It seems somewhat troublesome.
I don’t think it has anything to do with the new system I put on. I think it being a 13 year old car the relay and contacts of the air system were just dirty or needed cleaning. Since the light has went off with simply re-connecting a few things. The new system actually improved the cars feel in my opinion. Sounds nicer too.
 

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I'm still happy to not have the excess baggage of something else that can fail.

There really shouldn't be any performance difference with it working or not ........ not that I can imagine anyway.
 

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2003 chevy trailblazer_lt
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I don’t think it has anything to do with the new system I put on. I think it being a 13 year old car the relay and contacts of the air system were just dirty or needed cleaning. Since the light has went off with simply re-connecting a few things. The new system actually improved the cars feel in my opinion. Sounds nicer too.
I have a K&N intake as well, never caused any issues. What spacer did you use and do think it improved gas mileage?
 

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Discussion Starter · #9 ·
I have a K&N intake as well, never caused any issues. What spacer did you use and do think it improved gas mileage?
I bought a Taylor Cable aluminum spacer Helix design. It was expensive but seemed to have good reviews and build quality. I can’t say much about mileage yet since I just got the light off and haven’t had enough drive time to really test it. I’ll let you know once I can tell.
 

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I have a K&N intake as well, never caused any issues. What spacer did you use and do think it improved gas mileage?
You may be right. I have a special case of dislike for K&N because I have over time, had more than a dozen turbo diesels come into my shops with no boost.

Further investigation found the clean air/compressor fins were totally sand blasted to nubs from dirt getting through the K&N filter matrix.

If you run a rag around in the area inside the filter... you'll get grit and dirt. This isn't ever a good thing to ingest down the throat of the engine.

One thing ... I never found any dog poop, pine needles, golf balls, small children nor companion animals get through the filter... so it must have worked pretty good at excluding them.
 

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Further investigation found the clean air/compressor fins were totally sand blasted to nubs from dirt getting through the K&N filter matrix.
If you run a rag around in the area inside the filter... you'll get grit and dirt. This isn't ever a good thing to ingest down the throat of the engine.
I have a question, have the filter covers been installed?
 

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Actually.... a couple of the filters were on mix trucks with 36 inch long Racor prefilters on them and the K&N was a tertiary filter after a cyclonic sand trap. All those trucks went back to pleated Wix dry elements and never had that problem again.

A couple of 8.2 Detroits had also nubbed off their compressor vanes. The same common denominator was they used a cyclonic sand trap and a dry poly foam prefilter wrapped around the K&Ns.

I don't recognize the sock you've portrayed on that pix ... and perhaps K&N, realizing they had problems, retrofitted their inferior units with it. That may have come out after me retiring though.

The K&N filter company had sent outside sales agents to all the commercial companies with fleets of vehicles to build a "satisfied customer" base to prod for other testimonials. All their filters ever did was get me a lot more work, so in retrospect I guess I shouldn't bite the hands that fed me.

I've got a dozen or so K&N take-offs in my shop right now that I'm going to use for target practice. I wouldn't use a K&N to filter the air in my chicken coops.
 
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