Nissan Repair: O2 Sensor Heater Circuit Malfunction, suzuki grand vitara xl7, suzuki grand vitara

Question
Thank you for considering my question. It's a general question regarding O2 Sensor testing and replacement, and relates to a Suzuki, but there was no expert in the Suzuki Repair category to ask.

My wife has a 2001 Suzuki Grand Vitara XL7 (2.7L V-6). The onboard computer is showing the following codes: P0135, P0141, P0155, P0161. All of these codes are related to the O2 sensor heater circuits (all 4 sensors). The scan tool (an Autel  Geniscan GS100) also shows the same codes as "pending."

All repair manuals recommend removing and testing the sensors' resistance with a multimeter to determine which are good. Are there any other tests that might have to do with the heater circuit malfunction specifically? I understand it's unlikely that all 4 sensors went bad all at once, and that the problem is most likely with the pre-converter sensors. The vehicle has 58,200 miles and no driveability problems.

Thank you for your time and attention!

Regards,  Ron

Answer
Ron,

I would not think that all four would go at the same time either.  Therefore, I would check each wire to find which one is heated.  You probably have three wires.  One is the normal generation circuit and the other two provide power and ground for the heater circuit.  There is a relay that powers the heat for a small period of time and I would think the relay has gone bad.  Check it out and email me back.