After figuring we had a bad thermostat, we changed it, and flushed out the radiator and reservoir (it had gunk in it) that was yesterday, and as of today a SES light came on 5 MIN AFTER I GOT A FULL TANK OF GAS and gave me code p0420 and I found another one that is b0161. HELP! I realize that p0420 has something to do with the cat. but what do you guys think it is given all that we did and the gas? I really need help troubleshooting this and getting to the real issue here, and not just throwing parts at it. Also tonight I noticed that the radiator hoses dont seem to be very pressurized..
And what the heck is b0161, i cant find that code listed anywhere???

About a week ago we fixed the temp door actuator which was broken, thinking it would help fix the not working a/c (we have other leaks in the ac besides this to fix but thats not the problem), but then the heat stopped blowing....it now only blows cool or room temp air. all the fans are working, and all settings seem to work, it does get warmer a bit on defrost and defog settings, but not like it should. I tested it on a borrowed comp, and i tested the mix motor, and it got really hot when I engaged that, just like it should do on its own, what does that mean, what is a mix motor, and what and how do I fix it????
(this blazer was my late mothers who passed in october, and I don't have a ton of money to keep it going, but I would like to fix it. Thanks to all you guys for helping!)

2000 Blazer LT v6 4.3ltr 2 wheel drive with auto climate air

Again, thanks guys for helping us girls out!

 

Where did you buy that gas? A big station or a mom and pop carryout?

I found a reference to B0161 Outside air temp

 

at a citgo station. its an average size place. private owner. you think it may be the gas?

 

Only cat I ever lost... Citgo
Last week another guy had same as you.. guess it used to sell..

Probably not so much brand as how the owner maintains. All of them long time at place.. And if you cant remember their lot ever being dug up, avoid!

 

Amberly,

If Pettyfogs' reference to B0161-Outside air is correct, it will affect the way your Auto HVAC regulates output temperature. The outside temp sensor should show you the outside temp on the Auto HVAC controls and if it is wrong, will cause your issue.

Get that sensor problem fixed, (bad wire or bad sensor).

When your Auto HVAC shows correct outside temperature then your Auto HVAC should regulate temperature properly.

A TEST:
If you turn your temperature **** full hot or fully cold (to the last detent) then the system will ignore the outside sensor and go full hot or full cold with Hi fan speed. This will tell you if the unit can work properly once the temperature is reporting properly.

There are multiple temp sensors, so start with the one that has the code.

 

Well, hmmmm, I have been testing it on the all the way hot or cold side, not on the temp. and up on the thermometer, it shows the correct outside temp..... So with this in mind, should I still replace that sensor, or do you think it was a code that may have been tripped from the flush of the radiator and reservoir as well as the change of the thermostat?
Also, If so, where is the outside air temp sensor located?

 

I dont know where the thing is located but they are usually behind the grill. It's possible if you were doing a flush and got a spill on the sensor with car running, that caused the error setting the code as out of normal range.

This should help, look for wire color code, and measure {disconnected}

 

I have to correct myself and apologize if I confused anyone:
The Temp display on the HVAC controls I mentioned above is on the newer Trailblazer/Envoy Auto HVAC. (I have a 2000 S10 Blazer and a 2004 Envoy, both Auto HVAC)

On the S10 Blazers the Outside Temp display is always on the Rear view Mirror.

My 2000 Blazer has (2) sensors in front of the radiator, one for the mirror display and one for Auto HVAC, one is near the center and one off to the passenger side. Check both for proper connection and swap if you can to isolate the bad one.

 

For your P0420, follow this flow chart as written. It will lead you to the problem:

https://blazerforum.com/forum/diagno...plained-19820/