2001 Buick LeSabre Logo
Red Wymer Posted on Mar 30, 2015
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How do I find out Which Oxygen Sensor is Bad, Upstream or Down-Stream ?? I Pop 2 Error Codes. #1- Spark Plugs, #2 O2 Sensor(s) [doesn't designate which one as my Car has 2]

3.8L V-6 Started out as a Intermittent Issue, Service Engine Light ON, later it went OFF, after 3 weeks of this, Light stayed on Continuous. Took it to an Auto Zone they Plugged In and It Popped the 2 Codes (Sorry misplaced the Codes). Plan on Replacing Plugs anyways. But, on the O2 Issue seems to be a Puzzle, and I really don't want to R & R 2 Parts if I don't have too.

  • Red Wymer
    Red Wymer Apr 09, 2015

    Well Tried the Additive, and ran the Car for about 140 miles Freeway & stop 'n Go Traffic...Gas Consumption Decreased a Bit, Est. Mileage Increased a Bit, However still getting Hard Starting, AND Rough Idle (Cold)

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1 Answer

steve

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  • Buick Master 3,718 Answers
  • Posted on Mar 30, 2015
 steve
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With out the codes cant tell which o2 sensor is causing the issue , before you change any sensors i'd recommend using a fuel addative , get one that cover the catalytic convertor as well as fuel and engine parts , give it a long run at a good speed to get the engine to a high operating temperature as most o2 sensor issues are because the tip is coated in carbon etc and cant detect the exhaust gases, another thing to check before replacing o2 sensors is the air intake pipe work as a split , tear etc in the air intake side will give a false reading on the exhaust side as the intake readings are affected by the split , hope this helps

Testimonial: "I have always been a Firm believer in Seafoam, so would One (1) Can be ample in a 16 Gallon Tank, or Two (2) Cans?? When I add this additive would it be better to run a Higher Octane Fuel than Regular Unleaded??"

  • 3 more comments 
  • steve Apr 01, 2015

    Hi, i'm in UK and we don't have seafoam over here , the addatives i could recommend are WYNNS or REDEX , both are available on the internet if there not in your stores , as i said make sure you get one that covers the cat convertor as well

  • Red Wymer
    Red Wymer Apr 01, 2015

    OK, found the Codes: P0171, P0102, P0300

  • steve Apr 01, 2015

    Hi Red, the codes as follows P0171 Lean fuel mix,P0102 Low air mass input,P0300 random misfires, these all could either be caused by a faulty o2 sensor or a leaking or worn, split in the air intake circuit ,i would check very carefully all the air intake hose's especially the ribbed ones for any sign of wear etc , then if all ok i would go ahead with the fuel addative which MUST cover the catalytic convertor , keep me posted when you have tried these steps and good luck

  • Red Wymer
    Red Wymer Apr 09, 2015

    Tried the Additive, Est. Mileage & Fuel Consumption Improved a bit, However, it is still Hard Starting, and Rough Idle (Lower than required) on a Cold Engine. When it warms up to Operating Temp. Idle improves but still not smooth...Highway Driving is Fine, Around Town is a Bit Sluggish

  • steve Apr 09, 2015

    change the plugs as you previously intended and have the codes reread , if no better get the cylinder compressions read , dont know your mileage but 14 years old engine may have low compressions, there are a few things that could cause these symptoms , as cant see vehicle i can only suggest the next step i would recommend keep me posted

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Can a down stream oxyegen sensor cause a rich fuel and give me the po172 code on a 2008 chevy impala 3.

Hi Steven Mays, NO!
9TH GENERATION IMPALA.
THE DOWN STREAM IS JUST TO TEST THIS CAT ONLY
P0172- WAY TOO RICH FUEL TRIM, SCANNED.
A ENGINE + EFI QUESTION AND NO ENGINE TOLD.
3.? IS ENGINE?(typo)
YOU ARE REPLACING PARTS NOT ASSOCIATED WITH FUELING
02 FRONT IS YES. BINGO OR EXHAUST CRACKS NEAR THAT FRONT 02 SENSOR WILL CAUSE RICH ON 100 NEW SENSORS.
FOR A FACT.
THE LOWER INTAKE MATES TO THE UPPER WITH GASKETS THAT ARE NEVER REUSED. DID THEY?

IF DID THAT is WRONG, IT SUCKS AIR,CALLED A HUGE VACUUM LEAK. NO P03XX CODES, NO MISFIRE CODES DTC.
NO VIN TOLD , IT HAS THE ENGINE CODE. THERE.
NO BODY CAN GIVE ACCURATE ADVICE LACKING WHAT ENGINE IS THERE. BELOW GEN9 LIST
JUST GENERIC ANSWERS.
YOUR SHOP LACKS DIAGNOSTIC SKILLS FIRE THEM.
172 IS BANK 1 RICH,
CAUSES ARE MANY. (A generic v6 answer)
  1. no thermostat is good this old, if stuck at 150f sure will be rich.,
  2. fuel pressure too high. and bank2 not failing yet but will soon.
  3. o2 front sensor bad. bank1.only.
  4. 02 exhaust manifold cracks, making 02 there go full lean and EFI max rich, failed
  5. intake port gasket bad, and sucks air like mad and cause that cylinder to go max lean, (too much air) and now misfires, and that sends a slug of air to 02 front and confuse it (efi )
  6. injector leaks, any bank 1. or dead.we do the service manual injector balance test to find that.
  7. spark bad on bank 1,any. plugs bad or COP boot bad or HV wire sets if present.no engine told so must list all.
  8. if you drive 2 or 3 more driving cycles i bet more DTC errors pop
  9. like P0300 misfire.
  10. what I do, is , get engine hot, 180to200f, and make closed loop work on both banks.if not find out why with more tests.
  11. the real scan tool allows live watching PID scan LTFT on bank 1
  12. long term fuel trim. and will be slammed rich.(o2 stucklean)_
  13. then we loop 02 bank 1 scans and PID graph the 02 b1. for seeing it swing fast,(6 times a second )if not find out why here.
see next post for DSO scope 02 signals,or PID scans.




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0helpful
1answer

2005 Dodge Durango 4.7 giving a P0175 code. Could it be a leaky exhaust manifold?

Did you clean the Throttle body? That is often the cause of a rough idle.

The Fuel Air o2 sensor on the manifold is often hard to reach, but the downstream o2 sensor after the catalytic converter is easier to get to.

Code P0172 indicates Bank 1 of the engine has a rich fuel mixture. P0175 indicates Bank 2 of the engine has a rich fuel mixture. Engine Bank 1 is the same side of the engine as Engine Cylinder 1. Engine Bank 2 is the opposite side of the engine. A firing order and cylinder location diagram may be needed to see which side of the engine is Bank 1 or Bank 2.
P0172 is triggered by the engine bank 1?"upstream" oxygen sensor and P0175 is triggered by the engine bank 2 "upstream" oxygen sensor. The oxygen sensor alerts your system when the condition is too rich meaning there's too much fuel int the exhaust stream or too little oxygen in the exhaust stream. The symptoms and causes will help you determine the exact issue and how to fix it.
Your bank 1 or bank 2 sensors will be referred to as "sensor 1" or "sensor 2". Sensor 1 refers to "upstream" sensors, or the ones near the engine and before the catalytic converter. Sensor 2 is "downstream" or after the converter.

Location

https://www.google.com/search?q=2005+Dodge+Durango+4.7+engine+bank+2+upstream%E2%80%9D+oxygen+sensor+location

all about the code

https://www.google.com/search?q=2005+Dodge+Durango+4.7+P0175+code&

Battery condition?

https://www.dodgedurango.net/threads/05-4-7l-codes-p0172-and-p0175.77565/

..
0helpful
2answers

Where is the O2sensor bank 1 at with a code of P0420. AND do I need to replace both sensors upstream and down. Or just the one that is showing up on the obd scanner.

Bank one is front side of cat. It should also tell u if it's cat 1 or cat 2. Depending on make an modle an yr. Catalyst 1 bank 2 is left cat back sensor. Catalyst 2 bank 2 is right cat back sensor. U do not have to replace upstream also. My o2 sensor Catalyst 2 bank 2 went bad. Had engine code for burning rich bank 2. Replaced tha down stream sensor an fixed problem runs better an better gas. This was in 97 gmc suburban. Idk what vehicle ur askin about. An I'm not to familiar with much about cars jus trucks an suvs.
1helpful
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Where are o2 sensors location

One would need the year, make, model, and engine size to tell you exactly where they are and how many.

O2 sensors are always in the exhaust stream, either in the exhaust manifold that is attached to the engine, or in the exhaust piping after the exhaust manifold. Some models have one for each bank of the engine, and some have only one sensor to monitor oxygen content. These engine sensors that the computer uses to "fix" or adjust the air/fuel ratio are called the upstream oxygen sensors. If the car is equipped (as most are today) with an oxygen sensor after the catalytic converter, this is called a downstream oxygen sensor. They are the same and do the same thing, but the downstream sensor is only used to monitor the efficiency of the converter. The upstream sensor(s) are what the computer reads to adjust or "trim" the fuel delivery.

So some older cars have only one o2 sensor. Not far from the engine in the exhaust stream. Some newer cars with dual exhaust (2 converters) may have four o2 sensors. 1 for each bank of the engine and 1 behind each catalytic converter. A 2005 Buick Century with a 3.1L engine, for instance, has only two o2 sensors: one (upstream) in the exhaust down pipe, and one (downstream) just behind the catalytic converter.
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Error code P1131 & P1151

Hope this helps you or future parties of intrest. P1131 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1 P1151 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2 I would get under your stang and gently clean outside portion of o2 sensors using a scotch brite. Also if you have so dielectric grease pull electrical connections to o2 sensors clean them and add grease. These trick eliminated the o2 sensor OBD1 codes on my 1987 Ford mustang gt
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Cod 51 means o2 sensor is bad but tell me please which o2 sensor is bad .upstream or down stream sensor

Oxygen sensors code sometimes produced because of some other problem, blocked exhaust or cat converter, over rice fuel supply or vacume leak in intake manifold giving a real lean mix and so o2 out of range in both casesw
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How to fix 98 cadillac cater error codes

Reset error codes by disconnecting battery for 5 minutes. Start fresh. all codes should be clear now. drive and see if any new codes come on. They are the ones you need to address.
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Where is bank1 and bank 2 located on a lincoln LS?

On all cars, the bank 1 is where the first piston is...Your firing order on that car which is the first piston...Buy a chilton or a repair manual for your car and it will tell you which firing order your motor has....Its usually on the right hand side...Passenger side...Rule of thumb if you look at the spark plugs the one closest too you is usually the first piston....Bank 1 is located on the same side as the first piston...I hope this helps...
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How do I tell if i need an upflow or downflow oxygen sensor for my 2003 nissan altima 2.5l?

You need the code read to get the fault code

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What does po135, p1131, and p0305 mean on a ford f250 with a 4.6L 2007

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P1131 = Lack of upstream Heated Oxygen Sensor (HO2S 11) switch, sensor indicates lean (Bank #1)

P0305 = Cylinder #5 Misfire detected

It looks like you have two separate issues happening. Bank 1 would be the left side of the engine if you were standing in front of the truck looking at the engine. The "upstream" oxygen sensor will be on the exhaust pipe coming from the bank one side of the truck IN FRONT of the catalytic converter. From the codes, it appears that the upstream sensor has gone bad, but the oxygen sensor behind the catalytic converter, or "down stream" is fine.

The misfire on cylinder 5 on the right side of the engine, 2nd one from the front, could be something as simple as a fouled spark plug or a coil malfunction.

To identify if it is a bad coil, swap the #5 cylinder coil with another coil, and see if the misfire follows the relocated coil.
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