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I have an 2007 Honda Pilot 2WD with 139k mi. I changed O2 sensor (bank 1 sensor 2 - after the cat which was a pain in the ass to change due to the exhaust shield and lack of clearance for the o2 sensor removal tool) and both air fuel sensors near the engine with Denso after getting check engine codes P0137. I was averaging 15 mpg city before the sensor change and haven't changed the other sensors since I bought the car used at 90k mi. Despite changing the sensors, I still have the engine code P0137. I even changed the ground wire with an Everstart from Walmart since it looked frayed in one area. The battery (Interstate from Costco) was replaced within the last couple months. Any ideas what is still causing the P0137 low voltage issue? Thanks.
 

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I've had this exact code come & go, during a 1,600 mile highway trip. After the trip, it is not active (CEL is off at present). I'll scan for it this weekend to see if it is pending.

The PO of my '06 had an intermittent CEL that they never diagnosed, because in this case there were no mileage or running issues when the CEL was lit.

Just a data point. I (and the PO) thought it was simply a loose wire that was getting jostled. Now, not so sure.

You likely have this info already, for the causes (from P0137 – Meaning, Causes, Symptoms, & Fixes )
  • Faulty oxygen sensor (most common)
  • Short on voltage to O2 circuit
  • Exhaust leaks
  • Fuel pressure low
  • Engine running lean
So I'm not super helpful, but interested :)
 

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I have an 2007 Honda Pilot 2WD with 139k mi. I changed O2 sensor (bank 1 sensor 2 - after the cat which was a pain in the ass to change due to the exhaust shield and lack of clearance for the o2 sensor removal tool) and both air fuel sensors near the engine with Denso after getting check engine codes P0137. I was averaging 15 mpg city before the sensor change and haven't changed the other sensors since I bought the car used at 90k mi. Despite changing the sensors, I still have the engine code P0137. I even changed the ground wire with an Everstart from Walmart since it looked frayed in one area. The battery (Interstate from Costco) was replaced within the last couple months. Any ideas what is still causing the P0137 low voltage issue? Thanks.
If you can check the live data especially if you have a graphing scan tool and look at the O2 voltages and make sure your seeing rich lean flips. The second sensor should not fip as much as the 1st O2 sensor. If it looks sluggish, the CAT could be plugged etc. How were the terminals for the wires in the connector, clean, bent, loose? Did you check any of the harness to sensor wire for shorts? This is the wire from the ECM to the sensor, not the wires from the connector to the sensor. If you're up to it you can disconnect the O2 signal and ground wire at the computer and the O2 connector to check for shorts to ground and make sure the sensor is getting battery voltage. You're probably fine on the new O2 sensor. As for the engine being lean, possible, this is where live data would be great because it shows fuel trims on each cylinder. If bank 1 is running lean or has an exhaust leak before the O2 sensor it'll show up lean, low voltage numbers trending to 0.1 VDC. If your not having lean codes with bank 2 then the overall fuel pressure should be fine because fuel pressure reguator affects both cylinders so if you're only getting it on one side then it's wiring to the sensor, exhaust leak, or clogged injectors on bank 1 causing a lean condition. Hopes this helps.
 

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I have an 2007 Honda Pilot 2WD with 139k mi. I changed O2 sensor (bank 1 sensor 2 - after the cat which was a pain in the ass to change due to the exhaust shield and lack of clearance for the o2 sensor removal tool) and both air fuel sensors near the engine with Denso after getting check engine codes P0137. I was averaging 15 mpg city before the sensor change and haven't changed the other sensors since I bought the car used at 90k mi. Despite changing the sensors, I still have the engine code P0137. I even changed the ground wire with an Everstart from Walmart since it looked frayed in one area. The battery (Interstate from Costco) was replaced within the last couple months. Any ideas what is still causing the P0137 low voltage issue? Thanks.
Slightly off topic but you did bank 1 sensor 2? First time replacing a sensor but this is such a b****. Super hard to reach everything. The wire winds downward behind the engine and is secured by these clips/ties? I can't get to some of them. How did you get them off and get the new wiring through everything? The other sensors look way easier 😑
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the connector is on the rear cylinder head towards the #3 cylinder you have to access it from the top, next you have to pop the nylon clips out from their holes then you can release the wires from the clips by using a pin between the clip tab and the zip strip. use a crow foot o2 sensor socket.

OEMTOOLS 25249 Oxygen Sensor Crowfoot Wrench (greatnecksaw.com) You can get this at any auto parts store and Harbor Freight

You should be able to get in on the nylon tabs and the O2 sensor and wires out with these tools. Cheers.
 

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the connector is on the rear cylinder head towards the #3 cylinder you have to access it from the top, next you have to pop the nylon clips out from their holes then you can release the wires from the clips by using a pin between the clip tab and the zip strip. use a crow foot o2 sensor socket.

OEMTOOLS 25249 Oxygen Sensor Crowfoot Wrench (greatnecksaw.com) You can get this at any auto parts store and Harbor Freight

You should be able to get in on the nylon tabs and the O2 sensor and wires out with these tools. Cheers.
So when I bought the new sensor Autozone lent me their tool and that works good. It's mostly these clip things tripping me up. Do you know the generic name for those kinds of clips? Honestly not sure I will be able to reach one in particular, its hard enough to just see. . Will the new wire need to be clipped in? Thanks!
 

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So when I bought the new sensor Autozone lent me their tool and that works good. It's mostly these clip things tripping me up. Do you know the generic name for those kinds of clips? Honestly not sure I will be able to reach one in particular, its hard enough to just see. . Will the new wire need to be clipped in? Thanks!
I don't know the Honda part number or what them call them as I just remove them from the old sensor and put them in same place on the new wire. But I found them on Amazon.


You can also try these


Just look for a smaller bag.
 

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Well I just ended up cutting and pulling out the old sensor wire, and putting the new one through but I didn't clip the wire to anything. I have thin (and now very scratched) arms but there's just no way to access all the clips, or even see them with a iPhone flash-on video, much less than get a pin to any. The connector will be slid back onto it's bracket.
 

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I used a breaker bar, pb blaster, and the rentable o2 sensor socket set from Autozone the get the sensor out. I used lots of swear words and my iPhone to locate the connector behind the engine. It's slid on to a bracket just to the right of the connector for bank 1 sensor one. Some people on YouTube said to take the bracket off, but it's easier to keep it bolted on in order to slide the sensor down and off. You have to press a tiny tab on the bottom back side of the sensor and pull the connector downward. Once its loose, you push the bigger tab on the top of the connector to separate the sensor from the car plug.
 

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I just replaced both of my downstream sensors. The hardest part was the clips and sockets. I was able to unclip bank 1 socket from the bracket from underneath fairly easy. If you study the design and visualize it in your mind while you unclip, it will help. You cannot see it and will be working blind. You have to go back further than you would think and are reaching forward from behind the crossmember. If you have long skinny arms it will help. I used my thumbnail to pull the clip and pull the socket loose from the bracket, then from the top was able to unclip the plug from the socket. I used a long thin screwdriver to break the wire holding clips off. The new NTK sensors should have the clips installed already.
I used the crow foot socket on the front bank and the straight socket on the rear bank. That's the only combination that would work on my '07 4wd. It wasn't an easy job, but for me, it beats paying someone and I won't have to do it again for 150,000 miles.
 

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Discussion Starter · #11 · (Edited)
Update - it's been a few weeks since I changed the O2 sensor and both air/fuel sensors. I also put some berrymans b12 chemtool recently. The p0137 check engine light comes on intermittently now. I presume I have a clogged catalytic converter at this point since the check engine light went off not too long after I put the can of berrymans b12 chemtool in a full tank of gas and came back on today. I plan on taking the lacquer thinner challenge route (via Scotty Kilmer) and will put a gallon on klean strip(or rust-oleum) from Walmart into a half tank of gas and take a short road trip. Klean Strip is readily available at most stores, but rust-oleum would have to be ordered from Walmart.com. I've was averaging 15 mpg before I changed the sensors. I have an actron obd2 sensor and will check the live data on the o2 sensors when I get a chance. I will update again afterwards.
 

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Update - it's been a few weeks since I changed the O2 sensor and both air/fuel sensors. I also put some berrymans b12 chemtool recently. The p0137 check engine light comes on intermittently now. I presume I have a clogged catalytic converter at this point since the check engine light went off not too long after I put the can of berrymans b12 chemtool in a full tank of gas and came back on today. I plan on taking the lacquer thinner challenge route (via Scotty Kilmer) and will put a gallon on klean strip(or rust-oleum) from Walmart into a half tank of gas and take a short road trip. Klean Strip is readily available at most stores, but rust-oleum would have to be ordered from Walmart.com. I've was averaging 15 mpg before I changed the sensors. I will update again afterwards.
Just can’t believe the cat is clogged at 139k.
Id use only Denso or NTK O2 sensors. All else fails.
I’d clean connections using CRC Electronic Cleaner.
I’ve used tie straps to secure O2 sensor wires.
 

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Discussion Starter · #13 ·
Just can’t believe the cat is clogged at 139k.
Id use only Denso or NTK O2 sensors. All else fails.
I’d clean connections using CRC Electronic Cleaner.
I’ve used tie straps to secure O2 sensor wires.
I'm having a hard time wrapping my head around it myself. But, I've been avg 15 mpg since I got the car 6 years ago used. I take care of the routine maintenance (mobil 1 or pennzoil ultra platinum synthetic oil, air filter, ngk iridium spark plugs, etc), replaced the egr and pcv valve, and I can't explain the poor gas mileage. I throw in marvel mystery oil, seafoam, or berrymans a few times a year. I had all the classic issues (misfire on all cylinders, transmission issues) when I first got the car. Those issues were remedied with the NAPA coil boot spring and Valvoline Maxlife ATF . Maybe it's the gas I use. I usually fill up with Costco gas 87. I moved recently an they only sell 85 octane in my area. In either case, I don't have a p0420 code, but if my catalytic converter is clogged it would explain the poor gas mileage. Doesn't hurt to try at this point and I don't want to remove the cat and soak it in soapy water, yet. I didn't clean the connectors, which I wish I did when I replaced the sensors. The connectors were the hardest part of the removal process. I had a mechanic friend help me remove them. I'll let you know when my order of rustoleum lacquer thinner arrives from Walmart.com and let everyone know how it goes. The car drives fine and doesn't have any other issues aside from the p0137 and gas mileage. A side note, I put in some liqui-moly ceratec before my last oil change to try to improve my gas mileage. The p0137 light came on shortly afterwards. I'm 200 miles away from my next oil change, so I figured that this the best time to try the gallon of lacquer thinner before I change my oil without the liqui-moly.
 

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Discussion Starter · #14 ·
Update - I was at Costco getting gas last night and happen to speak to someone that owns a shop that does emission controls. (On a side note Costco gas hasn't introduced e15 gas yet. My area readily sells ethanol free gas and it's only 10% more than e10 gas.) I explained my situation and he asked what code the ECU was throwing - P0137. He asked how the car drove. I explained I ordered the lacquer thinner but haven't used it, yet (btw I decided to return it). I said the car drove great except for that pesky intermittent code. As mentioned in previous response, he said to check all my ground wires again. Push comes to shove, replace the ground connections with new star ones from an hardware store if need be. I plan on going to Walmart again today and replacing the two other ground connectors from the battery to the engine bay. My mileage has improved a bit since I replaced the o2 and 2 air/fuel sensors though but I'm still averaging 16 mpg overall. Hopefully check the ground wires and connectors will remedy the problem. He also mentioned that putting the lacquer thinner (Rustoleum since it was cheaper than Klean Strip from Walmart in-store) is only a bandaid and may burn out the substrate on the catalytic converters. Some days the car starts with the CEL and some days it doesn't. He even asked if I had a subwoofer and amp. He said he sees this issue from time to time. I hope I don't have to take apart body panels to see if there is a loose connection or corroded ground elsewhere in the car. Thanks for the feedback guys.
 

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On a side note Costco gas hasn't introduced e15 gas yet.
Good for them. Almost makes me buy a membership to a club that would have me as a member. :)



Original credit goes to Groucho Marx, however.
 

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Discussion Starter · #16 ·
I filled up at Sam's club last night (I have memberships at both Costco and Sam's Club - I like Costco better since their "no hassle" return policies are great. Sam's Club had a promo membership for $6 at slickdeals.net. Sam's club - to their credit since they are affliliated with Walmart - has a better selection on certain foods). I used to be a manager at a national gas station chain and spoke to the Sunoco Refinery person when they were filling the underground tanks as the Sam's Club gas station as they were closing. The person that own the emissions repair shop also worked at gas stations so we were all talking shop of the stupid e15 proposal after the gas station was closed to the public. Ethanol isn't good for fuel lines and engine internals, but auto manufacturers must be happy. I lamented that either go pure gas or pure ethanol, don't blend the ethanol into the gas (my personal opinion). Anyways, I switched from 10w30 to 5w30 (after using 10w30 for 6+ years) and my mpg improved to 20 mpg. My old neighbor is certified mechanic (that used to work for domestic car manufacturer) mentioned that some dealers sometimes put heavier oil in the engines to reduce wear and tear even though they don't tell the customer.


Good for them. Almost makes me buy a membership to a club that would have me as a member. :)



Original credit goes to Groucho Marx, however.
 
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