Toyota Tundra Discussion Forum banner

Short Term Fuel Trims

248 Views 1 Reply 2 Participants Last post by  Sefiro
Hey yall, reaching out everywhere I can to see if anyone has experienced this.

Back in January my cats were stolen. Everything was backordered for the unforseen future. Went with Stainlessworks headers and exhaust setup. Got the truck back and thought all was fine until one day at a stop light, the RPMs would fluctuate from 450 to 650 rpm. Didn't think much of it, figured the ECU/PCM has to learn the new setup. Fast forward to now and the truck was still doing it, so I figured I'd take to a reputable tuner with some Tundra tuning background and have him check it out.

He hooked up his HP Tuner and right away noticed that my short term fuel trims would go from -20 to 20 constantly, back and forth, up and down, and they would alternate; as one is going up, the other goes down, and when this occurs is when the idle rpms fluctuate. He did some tuning, changed some things and got the rpms pretty much stable but he was blind to the stft and the O2s at that point.

On the way home the truck threw code P0125 for open loop, still runs fine. I'm planning on changing the air filter, cleaning the MAF, and installing OEM B1 and B2 AFR sensors (I belive the ones installed currently are aftermarket Densos but u haven't pulled them to check, but they look like the new OEM ones I obtained).

Aside from that, what else could my issue be? Truck was perfect before the cats were stolen. I can't contribute it to a vacuum leak as the STFT constantly fluctuates and does just lean out.

Has anyone experienced this before with aftermarket header and exhaust installation? Truck is a 2015.
1 - 2 of 2 Posts
STFT are based on feedback from the front o2 sensors. They may be poor quality new sensors, or the pigrails were damaged by the saw.

The edu goes into closed loop when it receives proper input from all the sensors. The o2 sensors have to be heated and have a circuit in them for heating.

When reviewing scanner data, be sure to compare Fat to o2 signals.

Sent from my Pixel 5 using Tapatalk
1 - 2 of 2 Posts