2004 4wd Blazer, 79k, engine light came on 10-5 at start up. I went to Monro Muffler asap on way home as I didn't want to get stranded, but nothing else was going on with the Blazer, just the check engine light was on. Scan said oxygen sensor PO150. They replaced upstream right O2 sensor for total $189. 10-7, engine light on again, again to MM and they replaced O2 sensor, no charge. 10-9, engine light on again, again to MM and they replaced O2 sensor, no charge. 10-14, engine light on again, again to MM, this time they say both sensors bad, upstream and downstream, PO150 and PO140. This time they say dealer sensors are required as the after-market sensors didn't appear to be working and quoted a price of $174.83 each, but will deduct the first sensor price and 1st labor from the total. Still comes to another $326 on top of the first bill. Is this normal? Two sensors are more than my weekly unemployment check. Monro Muffler said they were "Special Order" from the dealer across town. I asked the dealer for prices and they said if I got both, they would be $140 each (after they quoted the MM price) and weren't "Special Order" (dealer restocking fee of 35%!). My brother says I'm getting rolled. Can I back out of having MM do the next replacement of the sensors as I didn't sign anything, just said I needed it done but had to wait a couple days for my UC check? My brother reset the computer by unhooking the battery for a while, so the engine light is off now.

 

Tell them to take the crap aftermarket sensor back and return your money. All of it.

You can get the AC Delco sensors for $60-$80 and install them yourself.

P0140 HO2S Circuit Insufficient Activity Bank 1 Sensor 2
P0150 HO2S Circuit Bank 2 Sensor 1

On a 2004, B1S2 is the post cat sensor. This could indicate a problem with the catalytic converter or a problem with the sensor.

B2S1 is the passenger(right) sensor. The first thing I would have done would be to switch the sensor side to side. If the code follows the sensor, then the sensor is likely at fault. If not, then it is a wiring or PCM problem.

If they are not actually diagnosing the problem and are just throwing parts at it, DO NOT go back. They will bleed your wallet dry.

 

Swartlkk,

Thank you very much for your help! The engine light came back on at start-up this AM again. I will take my brother's offer and let him help me with it (he's so busy I hate to make more work for him -he also owns two Blazers and restores old cars) and give him your information. And I will tell Monro Muffler that I won't have them "fix" it again, and hopefully I won't get any resistance from the manager. I have to drive 110 miles 5 days a week for schooling, so I pray that nothing breaks! (Or someone kills me with their driving habits!)

Kim

 

i said it once and i will say it again, do the job right or dont do it at all, MONROE MUFFLER, hence muffler shop everyone is in a bind these days and yes they are trying to rooke you, you have a cat issue get a cat put one up in there and be done with it. And for the record exspecially on blazers 2 o2 sensors will never go out at the same time so i would bring that up to them, NEVER AT THE SAME TIME