02 ground

cas23

Registered User
Where is the orange o2 ground on a 90 sc? is it supposed to be in the injector harness? i pulled the harness apart tonight to try to find it and found no orange wire. i see an orange wire going into one of the connectors near the pass side firewall. but it doesnt come out of the other side. is it possible somebody put the wrong injector harness in? i see it has 4 wires going to the o2 sensor but 90's are supposed to be 3 wire.

Thanks
 
3 wire o2 sensor should ground through its casing ... the Tan / orange wire is for the RH side o2 sensor back to the PCM. The ground is only for the o2 heater.


- Dan
 
I should still have this ground tho right. It's supposed to attach to the back of the drivers side head. And should I have 4 wires going to the o2 sensor on the drivers side. I thought I should only have 3. Is it possible that somebody replaced this harness.
I have no reading from the qh for o2 sensors.
 
The 4 wire o2 sensors on the SC normally ground to the PCM ( gray / red wire ), and the signal wire goes to the PCM - same with the ground for the o2 sensors, the ground for the Heater circuit on late models is actually on the Firewall near the battery - the early SC use a 3 wire and they ground through the o2 sensor. Sounds like somebody modified your harness in some way.


- Dan
 
ok gonna check it against a different harness to see whats up. thanks for the reply
 
Before you assume you've got a botched wire harness it's possible someone broke off the plastic tabs on the o2 sensor and used it on your setup.

They have teeth that direct them in; I've seen people grind off the plastic so they could use them in other applications.
Something to think about……
 
Also bear in mind that an extra O2 ground will not hurt anything. It might make it work better.
 
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