1990 Toyota Pickup Still have O2 sensor problem

BOXSTER617

MEMBER
1990 TOYOTA PICKUP

Electrical problem
1990 Toyota Pickup 4 cyl Four Wheel Drive Manual

Long story short.O2 sensore melted on exhaust and started popping efi fuses. Repaired wires since they were before o2 sensor plug. Fixed fuse popping problem. Engine light still on. Changed o2 sensor with Borg Warner sensor #OS601 and truck is popping fuses again. Are wires mixed up in plug? As of now, wires in plug line up as such, black to black, brown to gray, white w/red stripe to white, and pink w/green stripe to white. The first color is wiring harness and second is O2 sensor. This how they pair up. Or is O2 sensor bad?

1 Reply

KHLOW2008

MECHANIC
41,815 POSTS

Hi boxster617,

You should have followed up with your previous post so that the technicians concerned can response to you when notification is received.

For generic HO2S sensors the wire at sensor side is not indicated so you need to get the wiring specs from the manufacturer.

What is the trouble code you are getting now?
The popping of fuse indicats a possible bad sensor or wrongly installed wires.

Here is the test procedure for the sensor to see if the wiring is correct, at least for the heater circuit.

OXYGEN SENSOR HEATER TEST
1.Unplug O2 sensor connector. Using ohmmeter, measure resistance between sensor terminals. Replace sensor if resistance is not within 5-6 ohms at 68 °F (20 °C). See Fig. 12 .

2.A trouble code No. 21 is also an indicator of a problem in O2 sensor circuit. Trouble code No. 21 will set if O2 sensor heater circuit opens or shorts to ground on "HT" wire from sensor to ECU.

If the connectors as shown does not have any resistance, use the black wire to test for resistance with the other wires. Any that has the resistance shown is the one that should be paired with the black wire.