P2099 and P0174 codes, where to start?

johnnyquick · April 16

So, we were on a trip and truck was running great no issues and had put 1600 miles into the trip.

Driving along and truck went into limp mode with a P2101, P0152, and a P0300 code.

I had a Jet performance TB on it for about 40k and had sprayed cleaner into it and wiped it all out but did not remove it before trip, I also had cleaned the air filter and MAF sensor as well as changed the oil.

P2101 or P02101 was referencing a dirty TB or TB Actuator, so I took it off and cleaned it til it shined like a mirror inside and out.

Reset code and drove GREAT for about a day and a half then thru the code again, so I triple checked everything and was stressing out about driving home with trailer attached and it going into limp mode when on the freeway.

So I ordered a low priced Amazon alternative TB as where I was there were none locally in stock nor at the GM dealer.

It worked perfectly til we got home and now these 2 codes in the title came up and I reset em and they came back.

Where do you guys think I should start?

I can do most anything mechanically but don't want to start buying parts.

I looked up the codes of course and the likley culprits but I know there are some GM techs on here that may have a better gauge on things than a Google search or GMcodes.com ..lol

TIA Gents

asilverblazer · April 16

15 hours ago, johnnyquick said:

So, we were on a trip and truck was running great no issues and had put 1600 miles into the trip.

Driving along and truck went into limp mode with a P2101, P0152, and a P0300 code.

I had a Jet performance TB on it for about 40k and had sprayed cleaner into it and wiped it all out but did not remove it before trip, I also had cleaned the air filter and MAF sensor as well as changed the oil.

P2101 or P02101 was referencing a dirty TB or TB Actuator, so I took it off and cleaned it til it shined like a mirror inside and out.

Reset code and drove GREAT for about a day and a half then thru the code again, so I triple checked everything and was stressing out about driving home with trailer attached and it going into limp mode when on the freeway.

So I ordered a low priced Amazon alternative TB as where I was there were none locally in stock nor at the GM dealer.

It worked perfectly til we got home and now these 2 codes in the title came up and I reset em and they came back.

Where do you guys think I should start?

I can do most anything mechanically but don't want to start buying parts.

I looked up the codes of course and the likley culprits but I know there are some GM techs on here that may have a better gauge on things than a Google search or GMcodes.com ..lol

TIA Gents

Year, make, model, engine, drivetrain, mileage, etc?

It's an interesting combination of codes though.

P2101 throttle actuator control motor circuit, range/performance

P0152 O2 sensor circuit high voltage, bank 2 sensor 1

P0300 detected random or multiple cylinder misfires

P2099 post catalyst fuel trim system on bank 2 is reading as too rich

P0174 lean condition on Bank 2

Based on the total collection of codes, I would inspect the Bank 2 (passenger side), sensor 1 (pre-cat) O2 sensor, and wiring. It seems the sensor is messing up and producing abnormal readings (P0152, P2099, P0174), leading to possible miss fires (P0300).

johnnyquick · April 17

6 hours ago, asilverblazer said:

Year, make, model, engine, drivetrain, mileage, etc?

It's an interesting combination of codes though.

P2101 throttle actuator control motor circuit, range/performance

P0152 O2 sensor circuit high voltage, bank 2 sensor 1

P0300 detected random or multiple cylinder misfires

P2099 post catalyst fuel trim system on bank 2 is reading as too rich

P0174 lean condition on Bank 2

Based on the total collection of codes, I would inspect the Bank 2 (passenger side), sensor 1 (pre-cat) O2 sensor, and wiring. It seems the sensor is messing up and producing abnormal readings (P0152, P2099, P0174), leading to possible miss fires (P0300).

Sorry my bad.. 2020 Silverado 1500 6.2 70000k miles babied mostly all its life

silveradosid · April 17

the pre cat sensor is reading to much oxygen and the ecm is adding fuel to compensate which makes the post cat read rich. you either have an intake leak on bank 2 or possible weak injector which could cause the random missfires.could also be a valve problem, hook up a vacuum gauge and if it is steady around 18 to 20 then that would rule out the valves

asilverblazer · April 17

4 hours ago, silveradosid said:

the pre cat sensor is reading to much oxygen and the ecm is adding fuel to compensate which makes the post cat read rich. you either have an intake leak on bank 2 or possible weak injector which could cause the random missfires.could also be a valve problem, hook up a vacuum gauge and if it is steady around 18 to 20 then that would rule out the valves

THE ECM should be CUTTING fuel to resolve the P0152 and P2099, those are RICH conditions. Although the P0152 isn't exactly a 'rich' condition, it's an unexpectedly high voltage. That makes me think the P0152 (and P2099) isn't necessarily an actual rich condition, rather a faulty pre-cat sensor reading too high. The previous, code of P0152 means the ECM saw a voltage coming from the pre-cat O2 sensor that wasn't just high as in rich, it was so high that it was "circuit high voltage" - or outside the expected range. The ECM is now seeing a low(er) voltage from that same sensor (P0174), a lean condition in combination with the post-cat sensor reading rich (P2099). Those two codes can't really exist together, the bank is either rich or lean - not both. So which Bank 2 sensor do you believe?

The key here I think is the P0152, the pre-cat sensor is doing things it shouldn't, so I don't trust the P0174. Given that the two O2 sensors are disagreeing with each other, I am inclined to say the problem lies with one of them.