Re-Wiring the Second O2 Sensor

For a couple months my 1994 FZJ80 constantly had the check engine light on, the error code retrieved was always code 28, "Secondary O2 Sensor". I had a local shop (Berkeley Toyota in Berkeley, CA) replace the O2 sensors under recall, (SSC-S02) at about 98k miles. The problem remained. The shop gave me the run-around. Soon afterwards it started dying on the freeway, the 15A EFI fuse would blow. Four out of five times it died at highway cruising speed.

I looked under the truck and found that the four wires which descend from above the transmission to the second (innermost) O2 sensor were hanging loose enough to contact the front driveshaft, and the driveshaft had abraded them badly. What was left of the original plastic loom that shielded the wires was in tatters. All four were worn at least to the bare copper, the orange wire - a "hot" one - was worn so badly that the copper was completely gone at the contact point and only a shred of the insulation held it together. Whatever anchor the loom might have had was gone. I don't know if the Toyota service department saw the problem or not, but I think they must have.

One of the hot wires was coming into contact with the driveshaft long enough to ground itself and blow the EFI fuse.

I couldn't find an upstream connector for the four wires. I would have liked to have pulled that section and repaired it with solder on a bench. I was forced to fix it in a tight space. I used crimp connectors to splice in four new sections of 16-gauge wire, put heat shrink on the connectors, covered the whole bundle with new plastic loom and zip-tied the bundle out of the way.

After the fix the check engine light remained off and no fuses blew. I think I fixed it.


Morgan Fletcher
Back to Land Crusher