2008 Escalade P0455, P0172 & P0175, pulling my hair out.

[93M6Formula]

With LTFTs like that I'd say you have a massive vacuum leak. Check the intake and intake gaskets. Get a spray bottle and watch the trims or O2 sensor graph as you spray water around the intake connections and gaskets.

Wouldn't that cause a lean condition though? I thought about replacing the intake itself since this EVAP issues showed up after the valve issue and I can't find a problem elsewhere, and I used this intake on the 6.0 also. I don't know if debris may have poked a hole somewhere in the intake?

 

[Fless]

I had a thought -- believe it or not -- early today, showing that the coffee is working. Have you looked at the fuel ethanol content PID to see if the computer thinks there is more or less ethanol in the gas? Theoretically if you're not running any extra ethanol (over 10%) the computer might be confused about it. SWAG but something to check.

 

[93M6Formula]

Is it running the original carbon canister full of those wonderful carbon pellets?

I'm not sure on that honestly.

 

[93M6Formula]

I had a thought -- believe it or not -- early today, showing that the coffee is working. Have you looked at the fuel ethanol content PID to see if the computer thinks there is more or less ethanol in the gas? Theoretically if you're not running any extra ethanol (over 10%) the computer might be confused about it. SWAG but something to check.

I attempted to do this but apparently 6.2 powered rigs don't have a flex sensor. I thought the exact same thing and unfortunately it doesn't exist.

 

[93M6Formula]

This pretty much pinpoints it to a faulty sensor or actuator or the circuit connecting it. Do you have a way to monitor the VVT cam phaser (probably CMP), MAF, MAP, TAC and TPS to compare them all?

I do but everything seemed normal from what I was reading. Had it on a snap on scanner and HP tuners.

 

[93M6Formula]

It's the opposite -- the codes showed that the PCM was taking away fuel (negative trims) because the O2 sensors were saying it's too rich. With the LTFTs reset to zero, and the STFTs within 5%, there shouldn't be any rich codes. That is, unless the STFTs start going way negative again.

EDIT: so what is the remaining issue, hard starting?

Hard hot starts and low on power is the main issue. LTFTs are WAY negative and get worse the more miles I have on an oil change i've noticed too. Right now it sounds like it has a mild cam when you start it cold. I just cannot figure out what is making it run rich, and I assume this is what causes the hard start is because its just dumping fuel when it shouldn't be.

 

[Doubeleive]

Common Problems That Trigger the P0455 Code​

• Missing fuel cap
• Defective or damaged fuel cap
• Distorted or damaged Fuel Tank Filler Neck
• Torn or punctured Evaporative system hose(s)
• Defective Fuel Tank Sending Unit gasket or seal
• Split or damaged Carbon Canister
• Defective Evaporative Vent Valve and/or Evaporative Purge Valve
• Defective or damaged fuel tank
• Defective Fuel Tank Pressure Sensor

 

[Geotrash]

I attempted to do this but apparently 6.2 powered rigs don't have a flex sensor. I thought the exact same thing and unfortunately it doesn't exist.

It's typically a calculation based on input from the O2 sensors. I am 100% sure that the flex fuel engines like the L94 work this way, but only 80% sure that the non flex fuel L92 does. I own both. Lol.

 

[Fless]

It's typically a calculation based on input from the O2 sensors. I am 100% sure that the flex fuel engines like the L94 work this way, but only 80% sure that the non flex fuel L92 does. I own both. Lol.

Right, if it calculated ethanol at all it's a virtual sensor, not physical. I think the last physical sensors were either 2004 or 2005 (maybe as late as 2006, but not after that).

 

[petethepug]

Replace the carbon canister if your not sure. The clip below @ the 3min mark shows what gets into your fuel system. Amazon had the best price as well as free shipping for prime.

Is it running the original carbon canister full of those wonderful carbon pellets?

I'm not sure on that honestly.