I have a 2001 Chevy Blazer 4WD 4.3 liter engine it has a 102135 miles, and today will be the 3rd time in less than a month that it gets to go to the shop. The first time the guy replaced a bad o2 sensor and cleaned my mass air flow sensor, I got it back and had it for about a day and half and the damn service engine light comes on, I take it back into him and he "tinkers with it" calls me and says  I need a new air pump/smog pump because it burned up and that in turn burned up I believe relay or a fuse, I have had the balzer back for almost 2 weeks and last night the light came back on. I am starting to wonder if this is just a coincidence  cause of the mileage or if he is possibly messing this up on purpose.   What do you mechanics out there think?!?! Do you think I should get this fixed and then just turn around and try to sell it? I still have 4K on my loan.

The parts that he's replacing are common at that milage.

Best Money I've spent lately is on an OBD2 Reader.
Link to amazon

The prices at amazon change from time to time, I got the $80 for $40, so keep your eye on them.

That way if it put up a code you can read whats going on, and replace it if your feeing lucky. The o2 sensor is generally very easy to replace, I bet the labor would have paid for the reader.

-JTP

I think you should have done the 02 sensor yourself. Its two bolts and a plug

Thats what I am trying to tell my girlfriend is that it is the mileage, labor has costed me 65 bucks each time, My local auto parts store that my buddy works at has a reader than customers can use, if it is just another o2 sensor me and Mark can do it, which brings up another question, if we do fix it will the service engine light go off by its self or does it need to be reset and how would that be done?

If I would have known it was an o2 sensor and which one it was I wouls have done it myself

Lots of time something goes bad and causes the engine to run too rich or too lean. This cause a string of other things to go out.

How does the Blazer run?

Reason I ask is this:

On my car it had a rough idle in cold weather only (below 38F) and would throw a CEL.  It went to the mechanic a few times in an attempt to be fixed.  First it was the fuel pressure regulator, then he thought the fuel return line, and then the O2's.  Luckily on my car I can do a stomp test to read the CEL codes.  It kept throwing an O2 code and a rare AMF code (which the mechanic also read with his reader).  I replaced the O2's myself eventually to no avail.  

Here's the kicker:  What it turned out to be was the gasket that seals the throttle body to the intake was severely worn and letting excess air in.  I replaced that along with the intake gaskets and no troubles since.

From the research I have done, I found it was common for vac leaks to throw many different CEL codes.

ETA:  My car has 140,000 miles and is running strong.  And IIRC Autozone will read your codes for free.

Quoted: How does the Blazer run? Reason I ask is this: On my car it had a rough idle in cold weather only (below 38F) and would throw a CEL.  It went to the mechanic a few times in an attempt to be fixed.  First it was the fuel pressure regulator, then he thought the fuel return line, and then the O2's.  Luckily on my car I can do a stomp test to read the CEL codes.  It kept throwing an O2 code and a rare AMF code (which the mechanic also read with his reader).  I replaced the O2's myself eventually to no avail.   Here's the kicker:  What it turned out to be was the gasket that seals the throttle body to the intake was severely worn and letting excess air in.  I replaced that along with the intake gaskets and no troubles since. From the research I have done, I found it was common for vac leaks to throw many different CEL codes. ETA:  My car has 140,000 miles and is running strong.  And IIRC Autozone will read your codes for free.

Well I do on occasion use to different fuels from 2 differnent places. But to answer your question about the way it runs, it seems to run fine, no hard shifting, I still get about 19 mpg

This might lead you somewhere:

2001 Blzaer CEL problems

From the site:

Circuit Description: This is located under the radiator (pump, electric solenoid, and vacuum shutoff valve) and tees off up to the exhaust manifolds thru 2 check valves on 4.3L. For 4wd remove the front skid plate to access. The secondary air injection pump is used to lower tail pipe emissions on start-up. The PCM supplies a ground to the pump relay, which energizes the pump and the electric solenoid valve. Engine vacuum is applied to the shut-off valve when the solenoid is energized. The engine vacuum opens the shut-off valve that allows air to flow to the exhaust manifolds. Often the pump gets water/moisture in it and freezes up blowing the fuse and the check valves rust or freeze open internally and then burn thru the rubber hose, and even melt the lower “T”, shutoff, and even pump impeller.

Readiness codes are reset when check engine light is turned off.  OBD is running all its tests immediately afterward and finding new problems.

When it rains, it pours.  I see this sort of thing all the time.

The sensor it was using to evaluate some it its tests may have been borderline.  Then when you replace it, and its working properly, it finds problems that the last one didn't.

And don't forget the old standby that all mechanics are out to fuck you and he is breaking your car on purpose.

Quoted: Readiness codes are reset when check engine light is turned off.  OBD is running all its tests immediately afterward and finding new problems. When it rains, it pours.  I see this sort of thing all the time. The sensor it was using to evaluate some it its tests may have been borderline.  Then when you replace it, and its working properly, it finds problems that the last one didn't. And don't forget the old standby that all mechanics are out to fuck you and he is breaking your car on purpose.

How can I clear these readiness codes myself??

Either disconnect the battery for a few minutes or leave it alone.  Once the problem that caused the code is fixed the SES light will go away after a few start/drive cycles.

well right now I have the battery disconnected and I have taken off my skip plate and can see what I believe is my new air pump, every thing looks to be fine but I still can not find this fuse, maybe I should just put everything back together and just take it to the mechanic again!!!! I didn;t take it to him toady cause he was out of the shop on personal reasons.

The fuse is apparently between the battery and the fender.

Source

Quoted: The fuse is apparently between the battery and the fender. Source

It is too damn cold right now so I put every thing back and now that I read your source that you were so kind enough to look up for me I do remember that box. To hell with this, hopefully he can figure out the problem tommorrow and if it happens again then its going to the dealer. thank you for the replies and the future ones as well,

Ah yes the S-10 Air pump located under the radiator. my '02 S-10 Has thrown this code many times. First it was the vacuum selenoid connected to the air pump motor. It's $22. It had gotten wet and seized up. I acutally fixed it, but bought the new one anyhow. My air pump was still blowing so I thought I was done.

2 weeks later light comes back on. Find out it is the same code. I get all mad its' the same thing, but i took the whole assembly off this time (2 bolts) and checked all the hoses for leaks. turns out my air pump had gotten wet and rusted up. Stripped it down, and hit it with wd-40, then pumped some oil into the motor housing. Caulked the cover on so it wont leak again. It's been going 6 months so far.

The relay is under the battery tray, 2 or 3 bolts you'll see it under there.

Check your gas cap gasket for cracks, that will throw a code also. I have fixed all of the above, o2 sensor, gas lid, and front abs sensor on my 35k mile truck.

Well I took it back to the same mechanic and he played with his diagnostic thing and he could not get the air pump to turn on or off, so he turned off the service engine light and checked the fuse and it was blown, so now I have an appointment with the local chevy dealer on monday, cause now I am thinking it is electrical. guess we will find out.

Ask and ye shall recieve Really not that hard to do. We really see this when the weather gets cold. The fuse and relay is between the battery and pass side fender. You may have to take the battery out to get access. It is a tight fit.
  Document ID# 1874163
2001 Chevrolet Blazer - 4WD      


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Subject: LN2, L43 or L35 Engine SES/MIL Light Illuminated, AIR Pump Ingesting Water and DTC P0410 Set (Replace AIR Pump and Inlet Hose Assembly) #04-06-04-015A - (11/28/2006)



Models: 1999-2003 Chevrolet Blazer, S10

1999-2001 GMC Jimmy

1999-2003 GMC Sonoma

1999-2001 Oldsmobile Bravada

with Vortec 2.2L I4 or 4.3L V6 Engine (VINs 4, 5, W -- RPOs LN2, L43, L35)




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This bulletin is being revised to remove a part number and change the two AIR pump part numbers in the Parts Information. Please discard Corporate Bulletin Number 04-06-04-015 (Section 06 -- Engine/Propulsion System).


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Condition
Some customers may comment on the SES/MIL light being illuminated. Upon investigation, the technician may find a DTC P0410 indicating that there is a concern in the secondary air injection system.

Cause
Water may have collected in the AIR pump or the vent solenoid and frozen or corroded the pump.

Correction
Replace the AIR pump and install a new inlet hose and solenoid tube assembly using the following procedure:

Raise the vehicle on a hoist.
Remove the shield covering the AIR pump.
Remove the hose and vacuum lines from the pump and solenoid.
Remove the AIR pump inlet hose. Do not re-use the hose.
Disconnect the electrical connectors from the pump and solenoid.
Remove the pump mounting bolts and pump.
Transfer the isolators from the old pump to the new pump.
Install the new AIR pump and bolts to the vehicle.
Tighten
Tighten the bolts to 17 N·m (12.5 lb ft).

Route the new hose assembly up between the engine and fender. The hose should come up near the area between the battery and the coolant bottle.
Connect the new inlet hose to the pump inlet.
Connect the old outlet hose to the pump outlet.
Connect the electrical connector to the pump.
Connect the electrical connector for the solenoid to the connector on the new hose assembly.
Connect the hose with the white nipple to the vacuum source hose.
Connect the remaining hose to the shut off valve.
Install the shield covering the AIR pump.
Lower the vehicle.
Remove the coolant reservoir nut nearest the battery.
Route the new hose assembly between the battery and the coolant reservoir with the solenoid on top.
Install the solenoid bracket onto the coolant reservoir stud and reinstall the nut back into the vehicle.
Use a wire tie to keep the new hose assembly away from the engine. On four cylinder engines, tie to the AIR outlet hose. On six cylinder engines, tie to an available hole in the radiator fan shroud.
Parts Information
Part Number
Description
Qty

17803251
Pump Kit, Secondary Air Injection

2001 L35

2000-2003 L43/LN2
1

17803252
Pump Kit, Secondary Air Injection

1999-2000 L35
1


Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

J6050
Pump, Secondary Air Injection - Replace
Use Published Labor Operation Time




GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer".  They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle.  Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely.  If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition.  See your GM dealer for information on whether your vehicle may benefit from the information.
  WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© Copyright General Motors Corporation.  All Rights Reserved.


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  Document ID# 1874163
2001 Chevrolet Blazer - 4WD      

Well 711 dollars later i believe my car is fixed after going to the dealer, I had to get a brand new air pump from the factory cause the one the guy replaced with got water in it again, so I have a new air pump and a new hose that brings air into the pump, i guess it is configured differently than the old one to help it so no more water gets in, and hopefully I can get my money back on this broken pump that was rebuilt to begin with,

Secondary air injection system suckage.

1999 Blazer owner here.  Not had that problem but that thing has tested my mechanical skills.  

Quoted: Secondary air injection system suckage. 1999 Blazer owner here.  Not had that problem but that thing has tested my mechanical skills.

I just hope you never have to go through the shit I have.