2018 Silverado CEL After Towing

[Phishin]

2018 Silverado 3500
6.0L Gas with 80k miles

The about a year ago while towing a trailer my CEL came on. O2 sensor--Lean condition. Dealership changed the sensor. This weekend, CEL flashed back on, same thing. CEL is off now. I guess it reset itself.

Why would towing cause this? I think the sensor is probably fine? IDK. You guys have experience with this? Maybe the MAF sensor needs cleaned? Just guessing....

Have any of you Silverado guys seen this before?

 

[Phishin]

I should listed that codes:
P0137: O2 circuit low voltage (bank 1, sensor 2)
P2279: HO2S Signal Stuck Lean Sensor 2

 

[eljefino]

Maybe you got the cats good and hot and that somehow changed the computers expectations. Maybe the upstream sensor is lazy but it gets reflected in the D/S one.

 

[spasm3]

I believe there are 2 upstream sensors. A left and right bank. They probably replaced one of the banks, now the other side is bad.

 

[atikovi]

P0137: O2 circuit low voltage (bank 1, sensor 2)

Corrosion on a connector causing a voltage drop?

 

[tblt44]

Towing would not cause this. Did they change both pre cat/post cat sensors.
I just did both my pre csts do to a code. Saved the good one as back up

 

[SwampSurvivor]

Do you have any exhaust manifold leaks?

You'll be in the throttle more when towing. If you have an exhaust manifold leak, it'll be pushing a lot more exhaust out of the leak. It'll think it's lean and eventually trip a lean code.

I have a ford modular that loves blowing out the right side exhaust manifold gasket. It gets a very positive fuel trim when towing while having a blown out exhaust manifold gasket.

 

[HowAboutThis]

Maybe you got the cats good and hot and that somehow changed the computers expectations. Maybe the upstream sensor is lazy but it gets reflected in the D/S one.

When my 2002 Civic Si was driven up a long grade or under heavy load it would throw a cat code in it's later years. I think I've heard all the emissions stuff (CEL's) is super sensitive and doesn't always mean you have a major issue. Do you lug the engine when towing? Put the transmission in a lower gear to help keep from lugging? Drive fast uphill or into strong winds? Could just be something like that. Extra fuel or lean due to engine and systems being at their extremes pulling a heavy load. Wouldn't hurt to get checked out to be certain.

 

[Snagglefoot]

I have seen this happen with the drop in outside temperature. Not sure why the dealership claimed they often see CEL’s thrown then the temp drops in the fall.

 

[clinebarger]

I should listed that codes:
P0137: O2 circuit low voltage (bank 1, sensor 2)
P2279: HO2S Signal Stuck Lean Sensor 2

Do you mean P2270: HO2S Signal Stuck Lean Bank 1 Sensor 2??

 

[Phishin]

Do you mean P2270: HO2S Signal Stuck Lean Bank 1 Sensor 2??

yeah.... sorry. P2270

 

[Phishin]

My biggest issue with this CEL coming on is the huge hit in MPG's .... It's substantial. 20% more fuel being burned!!

 

[JTK]

She runs perfect in spite of this? No noises, skips, etc ever?

 

[Phishin]

She runs perfect in spite of this? No noises, skips, etc ever?

No problems.... Ever. Just the CEL comes on when towing with an oxygen sensor lean code and my gas mileage drops likes crazy.

Going to dealer on Thursday. They said there's an ECM update and they will smoke the engine to look for exhaust leaks

 

[clinebarger]

My biggest issue with this CEL coming on is the huge hit in MPG's .... It's substantial. 20% more fuel being burned!!

It's likely trying to "Light" the Catalyst, Which would burn a load of fuel if Sensor 2 is stuck low.

The 2 most likely scenarios.....
*The O2 Sensor is faulty.
*The Signal Circuit for that O2 is getting shorted to ground somewhere in the Harness. Yes.....I've seen pinhole sized rub throughs be intermittent.

Bank 2 Sensor 2 is usually more prone to Harness rub-through as it lays on top of the Frame Rail, Bank 1 Sensor 2 can rub trough on top of the Trans Crossmember.

After inspecting the Harness, Swap the Sensors side to side & road test under the same conditions to see if the DTC's move to the other bank.

 

[Phishin]

Well.....The dealer smoked the exhaust system and the engine and found no leaks. They replaced all 4 oxygen sensors, packed all the connections with dialectic grease (because of annual Krown treatments) and sent me on my way.

The bill was only $55, these guys take care of me.

 

[The Critic]

Well.....The dealer smoked the exhaust system and the engine and found no leaks. They replaced all 4 oxygen sensors, packed all the connections with dialectic grease (because of annual Krown treatments) and sent me on my way.

The bill was only $55, these guys take care of me.

 

[64bawagon]

View attachment 80895

That was my experience with the 6.0 we had at work. I tried everything I knew on the misfire but ultimately had to take it to the dealer, they threw so much stuff at it that they had no idea exactly what fixed it.

 

[spasm3]

I still think you had one upstream sensor replaced some time back, and the other upstream one started going out. All four 02 sensors for $55? Thats a freebie!

 

[Phishin]

View attachment 80895

LOL!!!

Yeah, but for $55, I'll gladly take 4 new oxygen sensors.