O2 sensor...Possible Fix

[Fatboy554]

I have a 1999 GMC Yukon 5.7 4WD and I'm getting a P0157 code which is bank 2 sensor 2 low voltage. I've replaced the sensor and still the same thing. The voltage fluctuates between 0.005 volts to 0.050 volts, sometimes it goes up to 0.080 volts. Now I'm thinking it might be a short somewhere in the wire, but I removed the wire loom and traced it as far as I could before it goes on top of the transmission and I can't reach it any more. The wires were perfect. No sign of damage anywhere. My question is which wire on the sensor connector supplys the voltage to the sensor and can I cut that wire and splice into the other o2 sensors Power wire and get the correct voltage? Any help would be greatly appreciated. Thanks.

 

[GoToGuy]

Bank 2 would be right side exhaust , and sensor no. 2 would be the after cat sensor. Is that the one your troubleshooting ?
Do you know how O2 sensor functions? The after cat sensor's function is checking catalytic converter health. It does that by analyzing the O2 content. Did you touch the sensor tip with dirty fingers or contaminate the tip with anti seize? The O2 level fluctuates therefore the voltage indication changes. Did the original sensor indicate the same readings? Check the wiring at the back of the engine and up to the main loom and continue. Any exhaust leaks?

 

[df2x4]

I'm no help but I'm interested to see what you find out. I have a very similar issue in my '97 K1500 Suburban, but only when I use the aftermarket remote start. If I start the truck with the remote it will sometimes throw rear O2 sensor related codes. If I start it with the key it's fine every time. Been meaning to look into it. My temporary "solution" was to use JET DST to set the PCM to only throw those codes if it sees the issue twice in a row.

If you haven't already, I'd download the '99 GM factory service manual. They have detailed diagnostic procedures and connector pinouts that may help you out. Free download on page 9 of this thread, post number 77.

https://www.gmt400.com/threads/88-98-service-manuals.43575/page-8

 

[Fatboy554]

Sorry I took so long to reply, but I did have an exhaust leak at the flange right after the bank 2 cat. Fixed the leak and now bank 2 sensor 2 fluctuates like the rest of the sensors at around 0.100 to 0.800. It still goes down low like it was at 0.050 but it goes right back up and fluctuates like the others. Thanks for the lesson on o2 sensors and pointing me in the right direction.

 

[Gmule]

I have a 1999 GMC Yukon 5.7 4WD and I'm getting a P0157 code which is bank 2 sensor 2 low voltage. I've replaced the sensor and still the same thing. The voltage fluctuates between 0.005 volts to 0.050 volts, sometimes it goes up to 0.080 volts. Now I'm thinking it might be a short somewhere in the wire, but I removed the wire loom and traced it as far as I could before it goes on top of the transmission and I can't reach it any more. The wires were perfect. No sign of damage anywhere. My question is which wire on the sensor connector supplys the voltage to the sensor and can I cut that wire and splice into the other o2 sensors Power wire and get the correct voltage? Any help would be greatly appreciated. Thanks.

Do you have the correct wiring diagram for your vehicle? You can ohm test the wires from the oxygen sensor back to the PCM and load test them without having to physically inspect each and every inch. if you find high resistance in one or 2 wires you could possibly overly the circuit without too much trouble.