Lean on bank one - S-Type Jaguar Cars & Trucks

unlikely to be a vacuum leak as the lean burn is recorded from the heated oxygen sensor(HO2S) in the exhaust manifold before the cat converter
Lean burn can be from low fuel pressures , faulty injectors
vacuum is created in the inlet manifold and is for all banks so if there was a vacuum leak the lean burn would be for all banks and all sensors

You said in your comment above:
"bank one is lean would that be the air flow sensor or an 02 sensor?"

Obviously you have the V6 engine and if bank one is lean and bank 2 is running correctly then it cannot possibly be due to the MAF. The MAF monitors air flow to the entire intake and cannot cause a lean condition isolated to one bank - just 3 of 6 cylinders.

It is unlikely to be an 02 sensor either and that can easily be tested for bank one. In fact it will be the oxygen sensor on bank one that is detecting the lean condition.

I would want a decent scan done on the engine and I would have a good look at the fuel trim readings, oxygen sensor data among others to see what irregularities are going on with bank one. I would also want to check that there were in fact NO issues with bank 2 which has not triggered the same lean fault apparently.

In your case, if only bank one has the lean condition I would suspect there is a vacuum leak only affecting bank one causing the lean condition but that will not be proven until more information is available.

Or you can just replace parts without identifying the true problem and hope for the best which I would not recommend.

It would depend greatly on which bank, if both bank are running lean I would suspect a MAF If only one bank is lean then I would suspect a intake manifold gasket. what Code or Codes do you have?

I’m happy to assist further over the phone at https://www.6ya.com/expert/brock_d67526d2a834c47e

P2197 - Oxygen Sensor Signal Biased/Stuck Lean Bank 2 Sensor 1
P2187 - System Too Lean At Idle Bank 1
P2177 - System Too Lean Off Idle Bank 1
P2195 - Oxygen Sensor Signal Biased/Stuck Lean Bank 1 Sensor 1
P2179 - System Too Lean Off Idle Bank 2

I am not sure what your Mazda is, but from the sounds of it, both of your Oxygen Sensors are shot. Replace them both, or check for vacuum leaks. It may be a good time to inspect and replace the PCV Valve and PCV Valve hose, too.


I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

code P1128 02 sensor bank 1 lean
code P1129 02 sensor bank 1 lean to limit
code P1133 02 sensor bank 2 lean
code P1134 02 sensor bank 2 lean to limit

fuel system is lean.

P0313 - Misfire Detected with Low Fuel
P0174 -System too Lean (Bank 2).
P0171 -System too Lean (Bank 1).

P0171 and P0174 mean "system too lean" for banks 1

Because you have a V engine the pistons are angled, More commonly known as a Bank, Now Bank 2 lean would mean that the righthand side as you look at the engine will be Bank 2, Lean means that bank is running rich, using more fuel

This can be caused by a faulty mass air flow sensor

P0171------ system too lean bank#1
Po174------ system too lean bank#2
For these 2 codes, try cleaning the maf sensor (mass air flow), that is mounted in the big black hose that goes from the air filter housing to the throttle plate, if it is dirty, that will cause those 02 sensors to send a signal to the computor to lean the air fuel mixture. If cleaning it doesn't work, the sensors will probably need changing.
P0300---- Random/multiple cylinder misfire
P0316---- Cylinder misfire at start up---- first 100 revolutions.
On those 2 codes, you have to do some testing to find out why there is a misfire.
Possible causes:
dirty/malfunctioning injectors
weak coil pack
fowling spark plugs/wires
Low fuel pressure