Getting (only) the following codes repeatedly, in order:

PO131 "Sens. Circuit Low Volt., Bank 1, Sensor 1"
PO171 "System too lean, Bank 1"
P1133 "Manufacturer Controlled Fuel and Air metering"

Mileage is slightly over 100,000 mi., stock engine/exhaust. The engine has not been molested in any way and was running fine prior to these codes and CEL showing up.

At this mileage I've read that it's a good idea to replace all the sensors(?). The front sensors don't look very easy to get a wrench on! What is the best type of wrench for them?

Now for your crystal ball - if a new left front O2 sensor doesn't fix the problem where would you look next considering everything I've described?

Note: Did find and correct corrosion on the left front sensor's connector pins - didn't help. Does the other end of the same cable plug into the ECU? Maybe some corrosion there? Looking for any/all suggestions!

 

I would say at 100K miles to go ahead and replace both the front sensors. They have a 60-70K service period!

 

If my car was stock I would just change the O2 sensors at the same time I changed the plugs - at least the front O2's.

 

Lots of miles on the OEM Sensors,, So, I recommend changing them.

Find the O2 Sensor Fuse (under hood fuse box Mini fuse 15 ) Turn the ignition switch to ON and Read the two test points on top of the O2SEN fuse to chassie ground and see what voltages that you read. It sould be exactly what battery voltage is.




This voltage is heater voltage and if the heaters are not working correctly, the sensor will fail prematurely or after the heater ciruit stops working correctly.

You can also disconnect the O2 sensor and read the ground wire to chassie ground to insure that you have the proper ground path. Tjhat SPLICE PACK is near the battery and has been known to have sever issues with corrosion:

Corroded from battery acid fumes:


Cleaned up:



BC

 

You can also data log the PCM and observe the sensor working correctly or not. They should switch from 100mv to 900mv

 

As always, Bill Curlee to the rescue! Thank you, sir, and I'll be checking that splice pack and voltage at the O2 fuse. Thanks also to Matt and WKMCD for their input on my well-worn O2 sensors.

Still would like to know if I need some special tool to remove the front sensors or will a common open-end wrench do it? Looks pretty cramped for space where they're located on the manifold!

 

The only Corvette that Ive had to have an O2 sensor wrench to remove the sensor from the OEM manifold is the C6 LS2 Corvette. The sensor sits inside a well in the manifold and requies the special wrench.

You should be able to use an open end wrench or a tubing flair nut wrench to remove it.

 

Answering my own question on what is a good wrench to remove the front O2 sensors on a stock C5. You really can't very well use a 7/8" open end wrench due to interference with the frame. Apparently there are two readily available types of O2 removal sockets which have a slot in the side for the wires to exit and stay out of the way. One is a conventional "deep" socket style. It's not likely that you could successfully use one of these on a C5 due to lack of clearance. The other type is very short and has an offset tab that accepts a 3/8" drive ratchet or breaker bar. These require less clearance and work pretty well. Harbor Freight has them for $7 (97177).

Another thing I discovered is that the heat from the resistive element inside the sensor is readily apparent to the touch. The heating elements are required to speed up proper sensor operation on a cold start and apparently a defective heater circuit can be a source of trouble codes. A simple way of verifying the heaters are working is to turn the ignition switch to the "on" position for about 5 minutes or so and then feel each sensor. The heat on the body of the sensor is easily detectable.

Last bit of info concerning my particular O2 sensor problem. While waiting for 4 new sensors to arrive I swapped the original left and right front sensor and the trouble code followed the suspect sensor. As a result of reading about all the things that might be the cause of my trouble codes I've been concerned that the problem might turn out to be something other than simply a bad sensor. Feeling better about that now.

 

You will be a SENSOR EXPERT after you resolve this issue!!

BC

 

Its lucky for me that I stumbled onto this post. I replace all 4 sensors on my stock 01 last night because I was getting a bank 1 no 2 sensor failure. Took it to my tech and he says that the same sensor is still showing low voltage. Is this a ground problem? Any help is appreciated.

 

LOW VOLTAGE??????????????????????? Low voltage what?

Heater circuit low voltage OR sensor output low voltage???

The GROUND is only associated with the sensor heater circuit.

The O2 sensor output does not have a chassis ground.

It uses a discrete circuit H2SO High and H2SO Low wire directly to the PCM.

You need to measure the voltage available at the fuse and the resistance from the H2SO connector to chassis ground. Should be zero ohms

 

Honestly, I just replace parts. My guy used his diagnostic to check all the sensors and the Bank 1 down stream sensor is showing .5 volts. This is the same sensor that he told me was bad before, so I replaced all. I fiond it hard to believe that I would have gotten a bad replacement and just happened to install it in the same position.