[:@] I have an '01 that has been frustrating. The CEL, TRAC OFF/VSC OFF lights are on. I understand that they work together, but what I have been unable to figure out, is why it's still giving me a Bank 1 too lean code? The local dealership said it was either an air filter, fuel filter, or o2 sensor. Well, I have replaced the air filter with K & N, fuel filter with stock, and am working on the o2 sensor.

Since this 'runner has California emissions it doesn't have 2 o2 sensors. Bank 1 is an Air/Fuel Mixture Ratio sensor, and Bank 2 is an o2 sensor. Since the code is calling for Bank 1, I have replaced the A/F sensor. It is still throwing the same code. I noticed that when I rev the engine at the EFI you can hear it hesitate and suck air from somewhere, before revving. What gives?

I have always owned a Toyota, but this is my first time with a problem like this. After the local dealership ordered the wrong part and tried to charge me $10 for a can of carb cleaner to "clean" the sensor, I thought I would take it somewhere else. So far, everyone is guessing, and frankly guessing is really taking its toll on me and my pocket book!! Has anyone experienced this, or do they have some idea what's going on???

Thanks,
BJSurveyor

 

do you have a vacuum leak somewhere?

 

How could I tell if there is a vacuum leak?

I have a friend, that owns a shop, hook it up to his scanner last night. The scanner said it was system too lean (Bank 1) Sensor 2. So, now I am going on the assumption that it is the downstream sensor. We left the truck run, and the downstream sensor wasn't giving any data at all. So, today I ordered the downstream O2 sensor.

This is an 01, built post 8/00, and has California emissions. The dealership that I talked to said that, with it being built so close to the change in production year, there are some quirks about what should be on the truck and what is on the truck. The diagram that he had showed sensor 2 to look like sensor 1, with a flange, and 2 studs coming off of the pipe. However, mine is different. My downstream sensor is threaded into the pipe with 1 nut. The dealership was a little surprised, but he said it happens. Everything on the truck is OEM, so it came that way.

I am changing the O2 sensor with OEM Denso, and plugs and wires with NGK. Hopefully, this fixes the problem. I'll keep you posted on my progress.

If anyone has any input, I'm all ears!! (Well, in this case... eyes!)

 

it sounds like an O2 issue, and if that doesnt fix it, you havge to have an air leak allowing too much air and not enough fuel.. had a crack intake pipe on my car, and it caused this issue