Check engine light code P0171

[B.A.F.]

I have two customers whose vehicles have shown this code. One has 100,000 miles and the other has 50,000 miles . The first is a 99, the second is a 00. Both cars run great and there are no driveability complaints from the customers. The code indicates lean exhaust from bank 1. I have tried a 20 ounce bottle of Techron in both and the light continues to come back after I have cleared the code. I am hesitant to change the o2 sensor without being sure because of the cost. Has anyone run into this problem?

[gbic1]

What type of cars are they? I have a 2000 Venture with same code and a friend just told me he had one with a split vacumn hose at the map sensor with a 3400. Going to check this one tomorrow.

[Brian R.]

For P0171 code (easiest and cheapest first)

1. Check your air induction system for leaks or broken hoses/connections.

2. Put some injector cleaner into a tank of gasoline and see if that helps after you've gone through a tank of treated gas.

3. Buy some no-residue sensor or electronic contact cleaner (NAPA or elsewhere). Remove the connector from the MAF meter spray both sides of the connector thoroughly. Spray the cleaner into every possible exposed portion of the MAF meter in the intake tube and let the cleaner evaporate. Reconnect the MAF meter.

4. Test the engine coolant temperature sensor - replace if out of spec.

5. Check the manifold absolute pressure sensor - replace if out of spec.

6. Check your fuel pressure (not too likely to be the problem).

7. Replace the HO2/A-F ratio sensor with the correct sensor (Bank 1 Sensor 1) - Get a part number from a Toyota parts department with your VIN.

8. Replace the MAF meter.

Somewhere along this process, the light should go out and stay out. Most commonly, it is cleaning the MAF meter and connector that solves the problem. Unfortunately, the light can go out for a short period and then reappear - making you think you solved the problem.

[gbic1]

Thanks, went to dealer and got their test procedure and traced it down to the MAF. No more code.

[Brian R.]

Originally Posted by gbic1

Thanks, went to dealer and got their test procedure and traced it down to the MAF. No more code.

Did you clean it or replace it?

[gbic1]

replaced after cleaning

[lodownlv]

injector cleaner fries o2 sensors. replace o2 sensors with botch will solve problem ive had this problem a lot!

[Brian R.]

Originally Posted by lodownlv

injector cleaner fries o2 sensors. replace o2 sensors with botch will solve problem ive had this problem a lot!

Not if you use good quality ones and use them according to directions. You are the first person on the Toyota board to make this claim. I think you should review your procedure for using injector cleaners.

[lodownlv]

so your saying no injector cleaner doesn't harm sensors and let me guess spraying carb cleaner through the intake on the maf wont harm it neither. come on man I'm telling you that some fuel injector cleaner fryes your o2 sensors don't deny my claim when its true.

[lodownlv]

the Chevron Fuel Injector cleaner with Techron is some good stuff and shouldnt harm your car nor the toyota brand that is dumped in at every 30k mile service by toyota. Dont go by the 99 cent fuel injector cleaner and yes it will burn up your sensors. next thing you know you can get some slick 50 and hope it fixed your thrown rod. LOL

[Brian R.]

Originally Posted by lodownlv

so your saying no injector cleaner doesn't harm sensors and let me guess spraying carb cleaner through the intake on the maf wont harm it neither. come on man I'm telling you that some fuel injector cleaner fryes your o2 sensors don't deny my claim when its true.

Don't put words in my mouth. Read what I said and that's all that I said. You want to bait me? Keep it up and see what happens.