I have a 2001 Blazer LS 4 door 4x4 which I bought new in 2001.

My "service engine light" came on, and I need to renew my plates soon which requires an emissions test in Wisconsin, so I need to address it asap. I had the codes checked yesterday at an Autozone, and it turned up P0410 "Secondary injection system fault." Three probable causes were listed on the printout in this order:
1. Circuit delay defective or fuse open
2. Check connector and wiring
3. Air pump defective or hoses blocked

Does this mean any one of these might be the source or that all of them are probably the sources? I'm not much of a DiY'er, but I don't want to get soaked by a repair facility. Any advice on some basic troubleshooting I, as a novice, can do so that when I take it in for repair I don't get taken advantage of? Thanks

 

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The Secondary Air Injection (AIR) System is designed to lower exhaust emission levels during a cold or warm start by injecting air into the exhaust manifolds. The AIR pump is timed to remain ON for approximately one minute after the engine is started.

What a PO410 means is that the car computer tried to do a routine test to verify that the A.I.R injection system works, and that the A.I.R. system failed the tests on both sides of the engine, twice.

Because the test fails both sides of the engine, this would seem to indicate a problem with something shared between the banks (the A.I.R. pump is a pump with an electrical motor that pumps air into both exhaust manifolds). Possibilities might be the fuse for air pump, the relay for air pump, the wiring for air pump, the air pump, the hoses leading from air pump to exhaust manifolds. Of course there are other possibilities, but those are the obvious ones that come to mind. Diagnosis should be logical and definitive before replacement of any expensive parts. The factory shop manuals describe extensive diagnostic tests to be used in conjunction with the Tech 2 scanner. It is also possible to diagnose without the scanner, but you have to be pretty good to make up your own testing protocol and to do this one must understand exactly how the system works.

As far as getting taken advantage of - the biggest risk you run is taking it to someone who is underqualified and does not know how to properly diagnose (or does not have the correct equipment). Most shops are well intentioned and try to please customers in order to stay in business. But ignorance can be easily perceived as someone intentionally trying to take advantage of you. Please keep this in mind when choosing a place to repair your vehicle. There are technicians, and then there are "parts changers" that will take a good guess and try a new part after pulling a code.

Below is some additional info that you really shouldn't care much about if you are going to take it to have it repaired - but this is what has to happen to set this code.

Good luck.

Circuit Description

The powertrain control module (PCM) commands the AIR pump relay ON by supplying a ground on the control circuit. This action energizes the AIR pump, forcing air into the exhaust stream. The PCM also commands the AIR vacuum control solenoid valve ON which applies vacuum to the AIR shut-off valve. When vacuum is applied to the AIR shut-off valve, airflow from the AIR pump flows through the hoses/pipes and to the exhaust check valves. The air then enters into the exhaust stream. The air that is introduced into the exhaust system accelerates catalyst operation by decreasing the time it takes for the convertor to begin its process of burning the incomplete gases; reducing engine exhaust emission levels. When inactive, the check valves and the shut-off valve prevent airflow in either direction.

The PCM detects a system airflow problem by monitoring the heated oxygen sensors (HO2S) and short term fuel trim during normal Open Loop AIR system operation. This is called a passive test. If the passive test indicates a pass, the PCM takes no further action. If the passive test fails or is inconclusive, the diagnostic will proceed with an intrusive or active tests. The PCM will command the AIR system ON during Closed Loop operation under normal operating conditions. The active test will pass or fail based on the response from the HO2S. A lean HO2S response indicates that the secondary AIR system is functioning normally. An increasing short term fuel trim value also indicates a normally functioning system. The AIR diagnostic consists of the passive test and the active tests. The AIR diagnostic requires failure of the passive and active tests on two consecutive key cycles to illuminate the malfunction indicator lamp (MIL) and store a DTC. If the PCM detects that the HO2S and short term FT did not respond as expected on one of the engine banks, DTC P1415 or P1416 sets. If the PCM detects that the HO2S and short term FT did not respond as expected on both of the engine banks, DTC P0410 sets.

 

Thanks for this information. I appreciate your adding that lack of experience/expertise can figure into the equation when seeking a repair. That's good advice. At the same time, I've been around the block a few times (literally and figuratively) and know that there are unscrupulous repair places out there, based upon direct experience and that of others whom I know and trust. So feedback and tips from anyone who's gone the route of using a repair business for this issue (or set of issues) is helpful as well.

 

Maybe check with BBB for your area - you can do that on-line. They should have a listing of complaints and if/how they were resolved. Probably there will always be some complaints no matter what because people tend to not understand - even if everything is legit. Question is how the shop resolves complaints and if they care. That should at least separate the "unscrupulous" ones you speak about from the well-meaning ones.

 

Thanks for the reminder about BBB. I'm familiar with with them. They are occasionally helpful if (1) the business is a member (but lots of businesses aren't, at least in my experience); and (2) the business member has numerous serious complaints against them (although in such cases the business generally has dropped its membership and the info is no longer available). A third issue is that BBB is slow to find a business at fault for a complaint because BBB's source of revenue is business memberships. So, it is not what I consider an objective source. I am also aware of online sources like Yelp and Google reviews.

A second question I'd like to ask forum members out there is if you have any sense of cost, for any or all of the items under the code? I have called a couple of places, but they will not do free estimates. Thanks.

 

OK I've had enough. You clearly don't understand anything about car repairs and automatically distrust anyone who can fix your vehicle. You have a very uninformed attitude, yet you think you and your friends know it all. I tried to help you. I'm done trying. Good luck!

 

MilwaukeeWoman1, What Les described in post #2, is a brief description of how the secondary air injection system works. It can be one of the most difficult DTC's to diagnose. The point is, that a correct diagnosis is critical in making certain that the repair is completed correctly, and as inexpensive as possible. The diagnosis process can be time consuming, and quite possibly more expensive than the actual repair itself. In addition to a good visual inspection, there are 11 pages of flow chart tests involved, and you can't expect them to diagnose it free of charge:
https://blazerforum.com/forum/diagno...plained-35146/

To request an estimate without first diagnosing the problem, isn't going to happen at any shop, if they plan on staying in business. The option would be to ask for an estimate to repair or replace all of the possibilities, in hopes that the problem would be solved.

The flow chart above is from the GM factory "dealer issue" shop manual. If you would like to diagnose it yourself, you will need to feel comfortable following the flow chart, and using the necessary test equipment. If you're not familiar with this type of diagnosis, trust me, you will develop an appreciation as to why proper diagnosis is so important, expensive, and worth it If you do choose this route, we can help you, that's why we're here.

 

Captain, you are a very patient man! Kudos to you. I just don't have that much patience with people when I see that they are inventing excuses to not listen to me! Makes me feel like I wasted time and effort.

 

Thanks, but I'm just trying to do my "job" as "moderator" I feel it was just a matter of miscommunication or misunderstanding on both sides. Bottom line is that we're here to help members solve problems with their vehicles: whether it's do-it-yourself information, how stuff works, or advice.

 

I usually have no problem paying for diagnostics, since I don't have all the know how and the equipment that a shop will have. Also, I have seen some shops that will waive the diagnostic charge if you get the recommended repair done. For example: When my crank position sensor went bad. They charged me .5 hour diagnostic fee, but since I had them replace it they did not charge me the diagnostic fee. Don't be afraid of all shops, there are several reputable shops out there. You have a 14 year old car, sometimes you have to spend some money to keep it on the road.