MSefi.com read only forum (Jan.15,2018)

What do I do with the extra wire on a 4 wire oxygen sensor? 2 go to the heater, one for the signal, do I just ground the extra wire? V3.0 MS with MS SnS. Thanks.

Dr.Hess wrote:What do I do with the extra wire on a 4 wire oxygen sensor? 2 go to the heater, one for the signal, do I just ground the extra wire? V3.0 MS with MS SnS. Thanks.

Yes. In my experience, the OEM Toyota harness has separate grounds for all sensors (O2, temps, MAP, etc). You may find it is already grounded via the exhaust manifold but I suggest a sepearte ground anyway to make sure you don't get flaky O2 signals.

Regards, Richard

G'Day, Richard. Yeah, I am pretty familiar with Toyotas. Especially 20v's. The OEM setup calls it a signal supply or something and it goes directly to the ECU. One of the heater lines is grounded to the sensor ground. I'll ground this extra wire too.

Thanks.