Oxygen sensors Bank 1 sensor 1 and Bank 1 sensor 3?

1996 CHEVROLET S-10
156,000 MILES • 4.3L • AUTOMATIC
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BRUCEDUNCAN
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I have trouble codes for 2 oxygen sensors Bank 1 sensor 1 and Bank 1 sensor 3. the last time I submitted a question the verification to my e-mail didn't go through. Last year no question verification was needed please go back to the old system. the new verification didn't work.

Please respond if you got this message o.k.

Thanks,
Bruce Duncan
Apr 30, 2026 at 11:05 PM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.
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BRUCEDUNCAN
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My o2 sensors one upstream one downstream both have 13.3 to 13.6 volts on the sensor side of the plug with the car running. Both sensors have heater resistance of 3.5 to 4.5 ohms. measured with the plug disconnected. My Chilton manual says 3.5 to 14 ohms is the acceptable range.

Please respond and I will to make sure the computer is working o.k. google chrome is the only browser that works on a lot of websites I use. When you respond I will give you the trouble codes.
Thank you very much guys you guys are great.
Bruce Duncan
Apr 30, 2026 at 11:16 PM
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STRAILER
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Hello Bruce, Can you please give us the codes numbers, this will help to make sure we are fixing the correct problem. Here is the location of the bank 1 sensor 1 location and sensor 3. Check out the images (below). Please let us know what happens.
Image (Click to enlarge)
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May 1, 2026 at 3:37 PM
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BRUCEDUNCAN
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Ken your recent link in my e-mail worked thanks. The above diagram doesn't apply to my truck. Sensor 3 is right sensor 1 is wrong. Bank 1 sensor 1 is on the driver side head pipe. Is there a way to clean the o2 sensor? Mass airflow cleaner? propane torch? There is 4 sensors on my exhaust. I am going to swap sensors from one location to another and see if the codes follow the sensor. I am looking at code: PO 133, PO143, PO 147. Bank 1 sensor 3 stayed at 24mv for about 7 seconds and then 7mv for 7 seconds. The hotter my truck gets the leaner sensor 3 gets.
May 7, 2026 at 1:50 AM
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STRAILER
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Yep I see that now on the image, #2 is the sensor the number 1 sensor bank 1, sorry about that. I would not try to clean the sensor I would replace it, does the truck have an exhaust leak? If so it will cause problems for the sensor.

P0133 — Bank 1 Sensor 1 O2 Sensor Slow Response
P0143 — Bank 1 Sensor 3 O2 Sensor Circuit Low Voltage
P0147 — Bank 1 Sensor 3 O2 Sensor Heater Circuit Malfunction

Sensor 3 is a heater circuit problem so cleaning it will not help, the other codes are response problems so the sensor may not be the problem at all if the tuck has an exhaust or vacuum leak. But I would check the wiring as well which can cause these codes. Here is a video so you can check for the vacuum leaks.

https://www.youtube.com/watch?v=LRKWV4Are5c

Please go over this guide and get back to us.
May 7, 2026 at 3:46 PM