I have a P0136 on my 1998 4Runner 2.7 3RZ-FE. It uses both narrow band sensors (pre cat and post cat) Looking at the waveform of the post cat sensor, often upon acceleration it drops to 0 volts. Common sense suggests that the pre cat sensor waveform should fluctuate as the mixture is cycling from reach to lean and the post cat should remain steady (if cat is working) but should it drop to 0 volts? ST fuel trim is about 3% whilst LT is -10.9%, I’m wondering if I’m dealing with a faulty sensor.. I used the Toyota Techstream since it doesn’t have a very good recording function I had to physically film the data, here’s a video of a short drive at operating temperature: Blue trace is pre cat sensor Green is post cat sensor Red is RPM Yellow is vehicle speed
I’ll appreciate any input.