rosslf

During my troubleshooting of a warm starting problem(yes it was the fuel reg, and I though I was the only one!) I bought OBDScan from Harrison R&D, I have found that both O2 on sensers on bank 2 read .8vdc at operating temp, while bank 1 O2 sensers continue to ocillates is this normal for the 4.8 engine? All sensers appear to function normally to ~190deg.F
I check a friends '03' with a 6.0 and all O2 sensers ocillates.
The truck runs great! 19-20mpg with 103k trouble free miles, minus the fuel regulator. Thanks for any info!

Lee 1278

It's normal for 02 sensors to give an oscillation reading as the exaust gasses are continuously varying with 02 content. I normally read 02 sensors on the AC scale on my DVM on the mv level. A flat .8VDC reading is an indication of a bad 02 sensor. Change one of the 02 sensors on bank 2 out. If that location starts to oscillate, good, change the other one too.

LanceM

Yep should oscillate, but I think but may be wrong that .8 is right around what it should oscillate at so your computer is thinking everything is happy, it's when they go bad and swing to one end that you get a too rich or lean mixture.

Lance

TheJamster1

Bank 1 Sensor 1, Bank 2 Sensor 1 are front or upstream O2s. B1S1 is Drivers Side, B2S1 is Passengers side. O2 sensors normally toggle up and down from the middle point (.45v or 450mv). A good working O2 will toggle several times a second, which they call crosscounts. The downstream O2s are B1S2, B2S2. They will toggle until the system goes into closed loop (computer controlled), then they should read low or below threshhold (.45v) if the Cat is good. A bad Cat, the downstream O2 will mimic the front O2s usually.