Banks 1 and 2 running lean, what can cause this. I doubt both oxygen sensors have died. Any ideas.

What engine?

I guess it must be the i6 since there are two banks. If it is, I just had this on my 08 last night. Turned out to be the oil separator PCV valve had failed and it was accompanied by a high pitched squealing sound. I did some Googling and causes are air leaks downstream of the MAF or problems with the emissions system. $125 for new separator (LR02377) and all is good again. One of the symptoms is a large amount of vacuum present if you remove the oil filler cap. Worth looking at as it only takes 2 minutes.

TXFireblade wrote:

What engine?

TXFireblade wrote:

I guess it must be the i6 since there are two banks. If it is, I just had this on my 08 last night. Turned out to be the oil separator PCV valve had failed and it was accompanied by a high pitched squealing sound. I did some Googling and causes are air leaks downstream of the MAF or problems with the emissions system. $125 for new separator (LR02377) and all is good again. One of the symptoms is a large amount of vacuum present if you remove the oil filler cap. Worth looking at as it only takes 2 minutes.

2 Mechanics later and 2 Land Rover specialist later I still have this problem.

Changed another oil separator and all 4 oxygen sensors....

Any more ideas please.

MAF sensor ?????

ok, a hard question thanks anyway.

Most of us are diesel men. FL2 MY10 TD4 GS traded in at 2 years
FL2 MY13 TD4 GS Current

Jason,

The fuel system is return less and the pressure of the system is controlled by a module that uses PWM to control the fuel pump.

PWM is very similar to Duty Cycle if that make more sense.

The Module is adjusting the PWM to get the pressure sending unit to the specified range.


If the pressure sending unit is not measuring the correct pressure then it could cause the type of problem that you are having.

My searching shows these part numbers

0261230110 Bosch
30756097 Volvo
LR005493 Land Rover (superseded by LR015294)
LR015294 Land Rover
1582665 Ford


Also if you have an ODBII scanner that can read the PID's check LTFT and post your findings here

Good Luck

Paul

Turned out to be the MAF sensor, Land Rover experts couldn't find the problem.

Jason,

That is very good to know.

Thanks for letting us know how you finally resolved the problem.

I will add that to my list of thing that can break on my 3.2

I don't think that I saw anyone on the Volvo boards replacing the MAF for 171/174 codes.

I need to check my fuel trim on my 3.2, I think that I am in specification (close to 0% and not greater than +/- 10%)



Did you do anything stressful to the MAF? Aftermarket air filter? Wading thru streams?


Thanks for sharing

Paul

Jason,

I did have theses codes on a different vehicle (not a 3.2 from Volvo/Ford/Land Rover depending on how you look at the world)

For that vehicle (GM 3800 V6) I changed the following to fix my problem

1. MAF

2. Catalytic converter


I didn't want to scare you so I didn't post that information.

For future reference here is what I found in general for 171/174

Note: this is not specific to any vehicle

Quote:

STFT Adaptation Value positive (+) (ECU thinks mixture is lean)

Consistent high positive value can mean bad MAF (reporting measured volume too low), low

exhaust back pressure, blown TWCC, misfires, large intake or exhaust leak (Large air volume).





Let’s look at some conditions that will set adaptations faults and there causes.

Intake air leaks

Incorrect Fuel Pressure

Injector valve defective or coked

Engine Temperature Sensor defective

EGR valve defective

Secondary air leak

Fuel evaporation control system defective or leaking.

Air Mass Meter defective

Vacuum leaks

Oxygen sensor aging (slow response)

Clogged or damaged catalytic converter

Contaminated fuel

Fuel tank ran empty

Combustion altered by a mechanical failure (Spark plugs, compression, intake/exhaust

valves, ...etc.)





Rear O2 Sensor Fuel Trim

The rear oxygen sensor, located after the catalyst, is used for fuel trim corrections on some

OBD-II vehicles



What if There Is No Vacuum Leak or Both Codes (P0171 and P0174) Set?
An "under reporting" Mass Air Flow Sensor can be a common cause of a code P0171 and P0174. Essentially, this means that the Air Flow Sensor is telling the computer that much less air is entering the engine than actually is.

Since the oxygen sensors are telling the computer that more fuel is needed, this causes confusion in the computer because the Mass Air Flow Sensor is still saying there is too little air and the Oxygen Sensor is reporting that the mixture is still too lean. The computer tried to compensate, but since resolution is impossible, it sets the code. It is important to restate that the Oxygen Sensors are accurate—the fuel mixture is too lean. In this case, the Air Flow Meter or Sensor is inaccurately reporting the real amount of air entering the engine.