MY deville 05 shows Code 171/174 Bank too Lean.How do u repair this problem

Here is a forum from Lexus owners discussing the same problems that you are https://us.lexusownersclub.com/forums/topic/64288-code-p0171-b1-too-lean

Lean condition bank 1 refers to the computers interpretation of information delivered by the o2 sensor for bank 1. Possible causes are many. First look at the sensor readings. You should see a fluctuation of voltage readings. If the sensor is not fluctuating it should set another code with it. The readings should be .05 v to about .455 volts normally. If the readings are lean then look at the fuel trims. They will likely be nowhere near 0. When the engine is right, the trims may go positive 3 to negative 3. If your short term fuel trim is say +18 and the long term fuel trim is say +20 at idle then try runnung the engine at a steady 1600 rpm and wait a minute till the readings level out. If they approach 0 then look for a vacuum leak. Let the engine idle and use choke cleaner spray to find the leak. Spray suspect areas and watch for changes in fuel trims.

Lean bank 1and bank 2, possible vacuum leak , restricted fuel filter or low fuel pressure.

Basically this means that an oxygen sensor in bank 2 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 2 is generally the side of the engine that doesn't have cylinder #1.
Note: This DTC is very similar to P0171, and in fact your vehicle may show both codes at the same time.
You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.
The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
I hope this helps.

P0146 pd means pending code
Pending codes and DTCs? Posted on November 12, 2010 by fcrmaster
When reading codes from your vehicle the fault code reader may show them as pending codes or normal Diagnostic Trouble Codes (DTC).
Pending codes (also known as continuous monitor codes) will be registered when an intermittent fault occurs. If that fault does not happen again after x number of start/stop cycles, the ECU will erase the code from memory. If the fault is persistent it becomes a DTC.
If you have read pending codes it is advisable to check the codes again after a week or so. If there is no apparent problem with the vehicle it is safe to erase the codes too and check back. But always make a note of any fault codes with the date and mileage of a vehicle.
If the codes read include a DTC then you need to investigate further. This you can either do yourself or advise your garage. If, again, you don't see an apparent problem (depending n the severity of the code) with the vehicle you can note the codes down and erase them. Then check again after a week or a few days depending on how often the vehicle gets used. If a repair has been made (previous owner) the DTC may just not have been reset after the repair.
The other numbers behind the code 01/06 , 02/06, 03/06 , 05/06 ,04/06 These don't mean anything . cheap code reader .
DTC P0140 HO2S Circuit Insufficient Activity Sensor 2
DTC P0146 HO2S Circuit Insufficient Activity Bank 1 Sensor 3
DTC P0171 Fuel Trim System Lean Bank 1
DTC P0174 Fuel Trim System Lean Bank 2
Sorry but this is something you should take to a qualified repair shop that has a diagnostic tool that can view sensor scan data.
Causes of lean condition trouble codes P0171 P0174 GM 5 3L

Replace the sensor your code indicates it is stuck in the lean position position their for it is malfunctioning bank two is the sensor O2 sensor before the cadillac convertor.This will resolve your problem.

defined as fuel trim lean bank 2. possible causes would be clogged fuel injectors, vacum leak or bad oxygen sensor

Anytime I get a too lean DTC I first change the fuel filter if it hasn't been changed in awhile. You'd be surprised how many times this has helped.

Good Luck with it.

Bob

change the air fow senser.

this code is to inform you that your fuel mixture on bank 1 is set or running to lean.