Help with o2 sensor testing

[GrayT]

96 chevy 1500 5.7
dual exhaust with generic cats, still has 4 o2 sensers

I am getting codes p1133 and p0135 (heater circuit fault bank 1 sensor 1)

I tested the harness on the drivers side after the cat and it only shows 10 volts.

Does anyone know why this would drop just 2 volts? any advice apreciated

 

[delta_p]

Both of those codes together sound like a dead or fowled O2 sensor to me because those codes are a result of the computer looking at the rich/lean and lean/rich switching, as well as the response time of the O2 output with respect to other temperature sensors like the ECT and IAT, engine run time.

if your system voltage at the heater connector, harness side, was 10 volts and you expected higher, then maybe there is a short somewhere with some resistance to ground (not a dead short) and is allowing a voltage drop.

The heater is hot in run and start, so if you key on engine off with a scan tool, the O2 output should gradually go lean (~.1 volts) from the initial (~.45 volts).

 

[Vjcamp]

Unplugged you should read battery Voltage on the Heater power wire on the Harness side, also need to check the Heater Ground Wire for a good ground anything more than perhaps more 40 mV on the ground side should be suspect. Be sure you have a good ground point for your voltmeter test lead when testing. Voltage drop is caused by high resistance: in a connection or even in the wire itself.

Also check the other side for comparision.

 

[Schurkey]

My '97 had multiple O2 heater failure codes. All that went away when I scrapped four O2 sensors and screwed new ones in.

 

[rangrayy]

I had this same problem on my '98. Truck was running rough too. Checked the codes and came up with the same.

heater circuit fault bank 1 sensor 1 is the upstream O2 sensor on the drivers side. Mine was burnt to a crisp. Popped a new one in and presto problem solved.