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Discussion Starter · #1 ·
I have a '99 MTX Cougar with almost 88,000 miles on it. I have just started to get a check engine light that goes on and off by itself. I have also recently been having trouble with my IMRC and have just cleaned and lubricated it, so I don't think this error code has to deal with it. The guy at Autozone checked the computer and it was giving off code P1131.....he said it has something to do with the Air/Fuel mix or meter. Has anyone else ever gotten this code or knows what I might need to replace to get it fixed. I would REALLY HATE to have to take it to the dealership,
 

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P1131: Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1

Sounds like a O2 sensor to me....
 

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oh boy!! sorry d00d, but i doubt u wanna know where it is?

know where ur firewall is? know where the back of ur engine is? seen that small space between the firewall and the back of the engine? if u see through that small space, u'll find ur winning ticket!
 

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its the killer up stream on the rear bank under the coil pack. There was a hot-to post a little time ago try searching up on it.
 

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Last month I searched for info on my P0420, and I concluded either my DPFE (Differential Pressure Feedback EGR), upstream rear O2 sensor, or cat was no good. DPFE seemed like better choice, so I spent 45 minutes swapping it. Two weeks later, code is back.

So, does my P0420 (Catalyst System Efficiency Below Threshold - Bank 1) mean same as his P1131 (Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank 1)? Should I shell out $85 on a new heated O2 sensor? What makes these things go bad? Should Insanity swap his DPFE first?
 

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Originally posted by: mallard
Last month I searched for info on my P0420, and I concluded either my DPFE (Differential Pressure Feedback EGR), upstream rear O2 sensor, or cat was no good. DPFE seemed like better choice, so I spent 45 minutes swapping it. Two weeks later, code is back.

So, does my P0420 (Catalyst System Efficiency Below Threshold - Bank 1) mean same as his P1131 (Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank 1)? Should I shell out $85 on a new heated O2 sensor? What makes these things go bad? Should Insanity swap his DPFE first?
I've got he P0420 and P0430 codes, I switched sensors already and the codes came back. If you want to test them before shelling out he money, you can switch the upper sensors and see if the code switches or comes back. If the error stays the same its probably your rear bank pre-cat. If it switches to P0430 then its most likely the sensor. Not sure on how the DPFE would play into that error. If anyone could clarify that it'd be much appreciated.
 

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www.bosch4less.com

Get the O2 from them, thats where i got my two upstream when i did my headers.

mallard: You code could be the O2 sensor failing or the rear pre-cat is bad... I would test the O2 sensor first to try to save some money.
 

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Originally posted by: mallard
So, does my P0420 (Catalyst System Efficiency Below Threshold - Bank 1) mean same as his P1131 (Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank 1)?
The Catalyst System Efficiency Monitor is the LOWER sensor - the one in the Y-pipe, UNDER the car. The Heated Oxygen Sensor is the TOP sensor - the one crammed up against the firewall.
 

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Originally posted by: Bennett9000
Originally posted by: mallard
So, does my P0420 (Catalyst System Efficiency Below Threshold - Bank 1) mean same as his P1131 (Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank 1)?
The Catalyst System Efficiency Monitor is the LOWER sensor - the one in the Y-pipe, UNDER the car. The Heated Oxygen Sensor is the TOP sensor - the one crammed up against the firewall.
So with that being said..it could be the lower sensor(P0420)?? Hmm..Are the voltage readings on those the same as the uppers?
 

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Discussion Starter · #12 ·
Ok, So should I fix this O2 sensor myself or just take it into the dealership because it is going to be a pain in the ass to get to and then after I fix it, the code could come back up again anyway? The car runs great, lol, I just HATE seeing those dummy lights on, really gets to me. If you guys really think it is just the sensor, I'll gladly do it myself. Lemme know...
 

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I would change the sensor yourself, nothings really "hard", just takes some time to do! :)
 
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