I have a 2006 Chevy Trailblazer LS/LT 4.2 liter 2wd. I have been trying to get it smogged, but can’t clear the code. P0171 - Lean Bank 1.
I’ve been having a parts throwing contest with it, but it has been winning and my wallet is losing.
I have changed the air filter, cleaned the MAF sensor, changed both O2 sensors, changed the secondary air valve and relay. I’ve done the carb cleaner spray test around the intake and vacuum lines, with no spikes in RPM.
Most recent try was a couple bottles of Techron concentrate with premium chevron gas.(still waiting to see if the code hits again)
Next steps are checking the intake bolts(to see if they are torqued) and intake gaskets, check for exhaust leaks at the exhaust manifold, and checking the MAP sensor.
I’m at a loss at this point, and can’t afford to take it to a shop.
Freeze frame data from the most recent hit on the code is below.
***Fuel system 1 - CL
***Fuel system 2 - NA
***Calc Load(%) - 30.2
***ECT(deg c) - 48
***STFT B1(%) - 3.9
***LTFT B1(%) - 22.7
***MAP(kPa) - 33
***Eng RPM - 809
***Veh speed(km/h) - 0
***Spark Adv (deg) - 10.5
***IAT(deg c) - 20
***MAF (G/s) - 5.82
***TPS(%) - 15.3
***Air status - NA.
Any help with this would be greatly appreciated.
Thank you in advance.
You don’t mention anything about the fuel system.
Some of things that can cause that code are, a weak fuel pump, a restricted fuel filter, and a defective fuel pressure regulator.
The vehicle runs perfect, does not have any intermittent rough idle issues or anything, I don’t have access to a fuel pressure test kit. There is no external filter on this vehicle, only the one in the tank.
You need to have the fuel pressure tested.
The fuel system in your vehicle is a returnless system.
The fuel filter and the fuel pressure regulator are part of the fuel pump assembly.
I’ll see what I can do, thanks
This is a known issue with these trucks. You will need to have the injectors cleaned with a cleaner that hooks directly to the fuel rail. Deposits foul the injectors and cause an uneven spray pattern that results in intermittent misfires and codes P0171 or P0174. GM has also issued service bulletins for this issue.
I advise you to have a shop hook up their evap/smoke machine to look for unmetered air leaks
Just because an engine is running smoothly, does not guarantee there are no leaks
The fact the code set at 48 degrees celsius means the engine was not yet warmed up, for what it’s worth
Like the others said, you have to have the fuel system tested
“changed both O2 sensors” . . . don’t take this the wrong way, but that was shooting the messenger
The oxygen sensors are merely reporting oxygen content. They are usually not the cause of lean or rich codes
“I’ve done the carb cleaner spray test around the intake and vacuum lines, with no spikes in RPM.”
That is an old school method, which doesn’t always work on modern cars
“The vehicle runs perfect, does not have any intermittent rough idle issues or anything”
That said, the carb cleaner spray test was not necessary. What you could do . . . watch the fuel trims while you spray carb cleaner
But the evap/smoke machine is more accurate for finding unmetered air leaks
Double check for an air leak between the MAF and the throttle body. The hose may be cracked in a hard to find spot or a breather tube could be loose. It may also be time for a fuel injection service as noted above.