Feb 16, 2011

Toyota 4runner CEL P0171 and P0120 Fixed

Image from yotatech.com

Disclaimer: This is for demonstration purposes only. Removing and mishandling the MAF Sensor can be a costly mistake. Some of these newer sensors go for a few $100. Proceed at your own risk.

Click here for an Update Oct. 7, 2011

P0171 - Fuel system running lean
P0420 - TPS sensor

Completely clean the MAF sensor *FIXED*!

CEL light went on in our '00 Toyota 4runner a couple days ago. 100K miles and going strong. Using Toyota Techstream Software with a Tactrix cable, 2 codes were read. So I figured if I replace the TPS sensor, clean the MAF, replace spark plugs, and then reset the ECU by unplugging the battery, then all would be fixed. Not exactly.

Even after replacing the TPS sensor and spark plugs, the codes kept popping up. Turns out I only cleaned HALF of the MAF sensor. I only cleaned the orange bulb and wires. What I forgot to clean was the internal wires of the MAF sensor. 

When looking down the long shaft of the MAF sensor, you'll see 2 thin looking wires at the end of the shaft. After cleaning the two hidden MAF sensor wires with CRC/11 oz. Electronic Cleaner and a Q-tip, a chunk of soot was left on the Q-tip.

I switched back the old TPS sensor, and reset the ECU again, and BAM, all was well. The car drove like it was brand new again. I'm very confident that our 4runner will be getting kick butt gas mileage once again.

PS: On another note, I made an error while troubleshooting causing the car's idle to run screwy. I left the radiator cap slightly loose causing the IAC to malfunction resulting in a rough idle. *Face Palm* Once the radiator cap was tightened completely, the car was back to 100%. Thought I'd throw this out there in case others run into the same problem.

1 comment:

  1. At least you have an idea on how to properly work with these kinds of car parts. Those who aren't sure on how to work with these kinds of parts should ask assistance from the experts instead.