My check engine light, VSC, and traction light all lit up yesterday. I pulled the codes and got P0172 and P0175

Background info:
I have an 06 IS350 and bought the car used w/ 40k miles. I have been changing my oil religiously with Royal purple 5w30 every 5k and the car has been running perfectly. Just last week, i hit 80k miles and decided to switch to 0w30 AMSOIL. 2 days later, my car felt sluggish in the morning but once it got to operating temperature, the car ran perfectly normal. Later that day, my dashboard lit up and I pulled the codes.

I have no engine modifications and did not touch the MAF sensor in anyway. I am certain the oil level is correct. Does anyone have any idea what could be causing the codes? is it likely that 2 O2 sensors could fail at once?

I have an appointment with the dealership on monday but i trust CL opinions more

 

I pulled up the code on the repair manual, you may try looking into the trouble areas, as it could be the a/f or o2 sensors, but hopefully some of this helps:

Last Modified: 6-26-2013 6.4 C Doc ID: RM000000WC300HX
Model Year: 2006 Model: IS350 Prod Date Range: [08/2005 - ]
Title: 2GR-FSE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0171,P0172,P0174,P0175; System Too Lean (Bank 1); 2006 MY IS350 [08/2005 - ]
DTC
P0171
System Too Lean (Bank 1)

DTC
P0172
System Too Rich (Bank 1)

DTC
P0174
System Too Lean (Bank 2)

DTC
P0175
System Too Rich (Bank 2)

DESCRIPTION
The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim consists of both the short-term and the long-term fuel trim.

The short-term fuel trim is fuel compensation that is used to constantly maintain the air-fuel ratio at stoichiometric levels. The signal from the Air-Fuel Ratio (A/F) sensor indicates whether the air-fuel ratio is rich or lean compared to the stoichiometric ratio. This triggers a reduction in the fuel injection volume if the air-fuel ratio is rich and an increase in the fuel injection volume if it is lean.

Factors such as individual engine differences, wear over time and changes in operating environment cause short-term fuel trim to vary from the ideal theoretical value. The long-term fuel trim controls overall fuel compensation. The long-term fuel trim compensates for long term deviations of the fuel trim from the ideal theoretical value. These long term deviations result from the corrections made by the short-term fuel trim.

If both the short-term fuel and long-term fuel trims are lean or rich beyond predetermined values, it is interpreted as a malfunction, and the ECM illuminates the MIL and sets a DTC.



I work at the dealer and am a CL member, would you be able to trust me? heh.

 

check the ohms on the bank 1 and 2 sensor 1's. should be like .8 - 1.4 or something close to that. anything under needs to be replaced.

 

thank you guys so much for the help! Im going to head over to my friends house to clean the MAF sensor to rule out that.

And yes, i do trust your opinion haha. That was what i was hoping was wrong with my car too, easiest fix.

I haven't heard of this but i'll definitely check this once i get to my friends house too. I just ruled out the sensors going bad because i got both p0172 and p0175, that means both sensors are reporting errors. The probability of both sensors going bad at the exact same time was a little too coincidental for me.

 

keep us posted!

 

Yea please keep us posted. Many others with the same type of problem

 

I cleaned my MAF sensor and did a reset by removing the negative terminal. I also checked to see if there was gasoline in the oil, luckily found none.

Im going to drive around for a few days to see if the codes pop back up. If they do, i'll be changing the oil back to 5w30.

 

I had random CELs and T/C icons pop up at odd times during my DD travels. I had previously read about gas cap issues on other owners cars and did notice that the factory cap on my '06 2IS seemed to be very flimsy. So I went ahead and replaced it with a new $6 Stant cap from Walmart. Surprisingly enough, I've not had the CELs and T/C icons pop up since! Just thought before doing any other more expensive fixes (ie O2 sensors, etc), you might want to give a new gas cap a shot.

 

Please do report back. I've had identical codes P0171 & P0174 almost immediately after installing my Joe Z intake pipe, pulled it & found it that it was running lean & ignored it for a while. It has been on & off since

 

i bet its the maf sensor.....I've had these codes NUMEROUS times when I was building my custom intake. Any oils or residue would cause it to throw the cels. I've considered getting a new maf sensor. This one has 113k miles on it, but a quick cleaning lasts me another 10,000 miles or so.

 

i have the same code today in my 07 is350 p0172. will clean maf and report back. any update guys?on how you fixed ur problem?

 

As I was driving home from work yesterday and my dashboard lit up like a Christmas tree... went to my local performance shop to get the codes checked out and i got the same ones the OP got (P0172 and P0175)

The car drives a little funny and feels like it bogs out at low RPM's and easy throttle but at WOT it acts perfectly normal. Another thing I have noticed is that the tranny shifts really hard, not sure if that is related to the car wanting to bog out at low rpm.

I do have an after market intake but I have never had issues with it in the past.

Any suggestions? I'm going to start off with re installing my stock intake and disconnecting the battery for a couple of minutes.

 

Well after thoroughly cleaning the MAF sensor, I have driven 2k miles and the codes have not popped back up. I think I'm going to make it it a habit to clean the MAF sensor every time I change my oil.

My car drove the same way before i clean the MAF sensor too

 

I'm going to put my stock intake back on and clean the MAF sensor to see if that helps. Not sure if my problems are in any way related to the engine overhaul that was just done last month. Or maybe it could be a tranny problem?

 

Went to autozone and picked up a can of MAF sensor cleaner and sprayed the sensor. Used up the whole can to make sure it was squeaky clean. Car started up and I drove her for a couple miles around city streets and fwys and I have to say that so far it looks like my car is running perfect!

Couldn't have done it without you guys!