Shane226

Hey guys, I know there are a bunch of threads on code 25, I've searched for th past two days. I just haven't quit found what I need so I decided to start my first thread. Last weekend I got a new to me 92 4x4 with the 3vze, and the check engine lights been on since then. It's showing code 25 lean. I tested the output of the o2 sensor and it seems to fluctuate between 0.1 and 0.2 volts at around 1500 rpms. But if I give it gas real quick it will read between 1.5 and 2 volts for a second. Does this mean I need an 02 sensor?

ksti

Welcome to yotatech.
Download the FSM for your vehicle www.ncttora.com/fsm/

There is a complete procedure to check o2 sensor properly.
Good luck

scope103

Good job checking the O2 sensor output first! It sounds like it may be working correctly; it is indicating a lean condition, and the ECM throws the correct code.

At 20 years, the O2 sensor could be iffy; they are easy to replace but not particularly cheap. But I would first run through the diagnostics given in the manual. AND I would check for a vacuum leak; extra air is sucked in after the VAF, leaning out the mixture beyond what the ECM can compensate for.

Good luck!

Shane226

Alright thanks guys. What's the best way to check for a vacuum leak on these motors? Sure is a lot of vacuum lines.