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Discussion Starter #1
Okay, I am getting codes for my o2 sensors popping up. It starts with bank2 sensor1(po155), then goes to b2s2(po156), then after a little while(100 miles or so) i get b1s1 (po135) then b1s2 (po141). My question is should I replace them all or could one bad one be causing a chain reaction for the rest to pop a code?..
 

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guesswork going like that im sure there is a way to test them someone can help you with but im not sure how to; usually it is from something else like plug wires, plugs, maf dirty, etc. how is it running
 

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Discussion Starter #3
Its not runnimg to bad, it could run better..I thought it was plugs/wires, so I replaced them (with good ones)..but Im still getting the codes. Havent cleaned the maf yet, may try that. Hopefully in the next week or so Im gonna get my exhaust work done , i really dont want to spend the extra $ on o2 sensors that dont need replacing ya know... there is not really a miss or anything while driving, my idle is like 800 in park and 500-550 while in drive or reverse..
 

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Okay, I am getting codes for my o2 sensors popping up. It starts with bank2 sensor1(po155), then goes to b2s2(po156), then after a little while(100 miles or so) i get b1s1 (po135) then b1s2 (po141). My question is should I replace them all or could one bad one be causing a chain reaction for the rest to pop a code?..
P0155 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
P0156 02 Sensor Circuit Malfunction (Bank 2 Sensor 2)
P0135 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

Dont see that often. All circuit malfunctions. Gee, did they all fail at once? Cleaning the MAF is a good idea but it wont help those problems.

And most likely replacing them all wont either.
so that leaves Check the wiring harnesses..

..I'm guessing that if 1 is causing it, it is bank 2 sensor 2. Unplug it and see if the others go away
 

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^^ Yep. I would make sure they are all getting power. It is very unlikely for them to all fail at once. If you need a diagram, I can probably scan one in for you tomorrow.
 

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Discussion Starter #7
Thx ..I thought is was weird that they all pop up at the same time.. I will get under it and check the wiring as soon as it stops raining... All i got is a cheap scantool that gives me the codes and a program that gives a generic description. I will def. have to chase this down. I think its causing me fuel usage..
 

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Discussion Starter #8
Okay , finally got under it to day..only one loose wire that runs from bank one sensor one up to a part by the fire wall..I will try and post a pic of it asap. I cant find where it hooks up. I did realize that bank 2 sensor 2 was replaced at one time as it looks totally diffrent than the rest. I rechecked the codes today after clearing them , this is the way they came on my scan tool---
po135,po141,po155,po156,po161...let me know what you guys think..and I will try to get that pic posted in just a few..
 

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Discussion Starter #10
After reading other post with the same issue, i may just take a chance on buying a PCM repacement...I still would like to know what that wire goes to...mmm
 

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That wire is the auto climate temperature control heater lock out wire, it goes to a sensor on the coolant tube hardline behind the intake manifold between the two cylinder heads, but only on semi-automatic temperature climate control units.

If you have 3 knobs on your ac head unit that wire is unused, all thunderbirds are pre-wired for that connection. However, if you have a 2 dial ac head unit with a digital temperature read out then that wire is used to prevent cold air from blowing out of the vents ONLY when the heat is selected AND ONLY when the fan speed setting is in the AUTO position.

This "feature" is only used in an example similar to this: It's 20 degrees outside, the car has been sitting outside all night. Turn the car on, select AUTO for fan speed, select vent position, select desired heat ex: 80 degrees. No air will blow from the vents until the coolant is hot enough to warm the 20 degree air to your desired 80 degrees. However, this feature is immediately bypassed by not selecting the AUTO fan speed. If you turn it to anything other then AUTO then cold air will blow out of the vents and continuously work it's way up to the desired/commanded temperature.

So in short answer if you have semi-automatic climate control in your MN12 the purpose of "that wire" is to keep cold air from blowing out of the vents until it has the ability to when used in the auto position. In all other fan speed positions, and MN12's with standard climate control that wire does nothing.
 

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Discussion Starter #12
I was thinking that it didnt hook up, I was thinking right. I dont have auto temp..sooo Looks like Im replacing the PCM then. Thanks for the quick response on the wire issue.
 

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I was thinking that it didnt hook up, I was thinking right. I dont have auto temp..sooo Looks like Im replacing the PCM then. Thanks for the quick response on the wire issue.
No problem
 
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