Help please, 2001 Toyota Sienna P0174 (System Too Lean [Bank 2]) code - Toyota Tundra Forums : Tundra Solutions Forum

jeffsmith2002 · #1 (**permalink**) 11-23-2005, 04:19 PM

Every 3-4 weeks the Check Engine Light on our 2001 Toyota Sienna LE comes on, diagnostic checks have indicated, all four times, the P0174 (System Too Lean [Bank 2]) error code. Cleaned the MAF Sensor, but that didn't help. Air filter is new. Any ideas what I might try next?

mustang67408 · #2 (**permalink**) 11-23-2005, 06:10 PM

Your going to need a scan tool and see what kind of voltages the BANK 1 & 2 AIR fuel sensors are producing. You probably have a bad A/F sensor BANK 2 sensor 1. (this is the bank closest to the radiator.its the top a/f sensor before the cat converter).
You might also want to check fuel pressure (low fuel pressure will cause this too), and have the battery checked as well. I have found that low batttery voltage will cause havoc with many sensors.
Make sure you have no vacuum leaks or hoses that are off or cracked.

04ToyoTundra · #3 (**permalink**) 12-04-2005, 03:30 AM

check the resistance on the oxygen sensors. usually the cat goes bad.

dwaynedulci · #4 (**permalink**) 03-26-2007, 06:09 PM

I am having BOTH P0171 and P0174 codes appear. They are the same problem but one is bank 1 and the other bank 2. I have checked my vacuum hoses and duct work fairly well and did not find any cracks or disconnected pieces. My manual indicates "incorrect fuel pressure" as the next most likely culprit. I am going to run a pressure check on the fuel system and see what it reads. If any one has any tried and true solutions, please let me know. I will post back and update the results of the pressure check.

mustang67408 · #5 (**permalink**) 03-26-2007, 06:26 PM

Quote:

Originally Posted by dwaynedulci

I am having BOTH P0171 and P0174 codes appear. They are the same problem but one is bank 1 and the other bank 2. I have checked my vacuum hoses and duct work fairly well and did not find any cracks or disconnected pieces. My manual indicates "incorrect fuel pressure" as the next most likely culprit. I am going to run a pressure check on the fuel system and see what it reads. If any one has any tried and true solutions, please let me know. I will post back and update the results of the pressure check.

Take a fuel sample also, Make sure you didnt accidentally get any E85, or diesel, Toyotas will not run well on that and run very very lean on E85 which is what those 2 codes represent.

If your sure you have the correct fuel, then you are on the correct path to check fuel pressure.

When the DTC P0171 or P0174 is recorded, the actual air-fuel ratio is on the lean side

I would also check the MAF for a foreign object or debris and also clean it.

Make sure the A/F heater relay is also working.