2002 X5 4.6is Supercharged, two codes left
 

Hi Gang,

Almost one year ago I bought a 2002 BMW X5 4.6is, Supercharged. When time allows I 've been working through the bugs of this aging super-model and have just finished the intake manifold job, and any gaskets going in. Also did the fuel injector o-rings.

I drove 100 miles last night and two codes have returned:

P0175 - System too rich, bank 2

P1149 - H 02 S Bank 2 signal, too high

What should I be looking to replace, both O2's on bank 2? Or just downstream?

Thanks guys!

2002 X5 4.6is Supercharged, two codes left
 

What's the realtime value on the O2?

It should be between 0.2 and 0.8. I would replace just the wonky sensor. It's very rare you get a code specific to the O2 usually it's the symptom not the cause.

Having both errors same bank does hint that the front sensor is sending the wrong amount of gas. Easy test is to swap front sensors see if the code/s flip to the other bank.

I would look at the short term and long term fuel trim for bank 2. The fact that the 02 sensor triggered a P0175 does not mean that it is a bad sensor. Could be other items causing a rich condition such as a sticky injector. Find out what the problem is before firing the parts cannon.

Here's a pic :

Short term fuel trim is spot on but long term fuel trim is -25 so the DME is taking away fuel which indicates a rich condition. Does the long term fuel trim go down when you raise the rpm and hold it for a minute or two?

What type of gas are you using? Ethanol gas aka gasohol?

Ill have to check tomorrow.

Shell 93 & Seafoam

wow that's very rich. Rich on both banks; i would first check the basics; what is fuel rail pressure? it's uncommon for the MAF to be off but both your banks are quite rich so it's systemic even if only one bank reported an actual error code. Look at your realtime MAF numbers and maybe find the xo thread where people reported their MAF readings for control comparison.

Post the ECT (Engine Coolant Temperature) once the engine has warmed up. Don't go by the temp gauge on the cluster. You can scan for the ECT PID. An engine that fails to warm up to operating temp will always run rich. Back in the old days before EFI a CHOKE either manual or automatic was designed into the carb to provide a rich mixture for a cold engine.

Hmmmm. If ECT never gets high enough will the brain keep the engine rich? I know my remind ran rich for months because my thermostat was stuck open. Make sure you're getting to closed loop

Even in open loop the fuel map uses the ect to determine the fuel mixture. Close loop is when additional sensors like the 02 sensors are used by the DME to adjust the mixture. To aid in going into close loop sooner heaters are incorporated into the 02 sensors.

You answer this question yourself when you stated your car ran rich when you had an open thermostat