O2 Sensors

[custodian]

First off, the tune I'll be talking about is a basic 5.3/4l60e LS Swap tune I'm using in my 73 C10. Now the issue. when I come to a hard stop, slam on the brakes, I get a MIL light. I've checked the codes and it shows both O2 sensors not functioning. I get both sensor codes at the same time. I don't get the MIL light during normal driving. I've checked the live data and it shows that both O2 sensors are putting out a reading/fluctuating. I'm only running the front two sensors and they are for a 2002 Silverado with the 5.3. Any thoughts on what may be causing the MIL light to come on?

[ralmo94]

I don't know, but if you post the code numbers, that might help someone have a better idea.

[custodian]

I don't know, but if you post the code numbers, that might help someone have a better idea.

I didn't write them down, I'll do that the next time it throws a code.

[Pulse_GTO]

You say that both O2 sensors are not functioning. What are they doing when not functioning? Flatlining at 450mv? You may be having a ground issue depending on what type of harness you are using, whether the sensors are case grounded or isolated grounded. Here https://www.lt1swap.com/vortec_o2_sensors.htm is some info about that. I'm thinking that they may be losing ground somehow when you are slamming on the brakes. I know it's far fetched, but may give you something to check out.

[custodian]

You say that both O2 sensors are not functioning. What are they doing when not functioning? Flatlining at 450mv? You may be having a ground issue depending on what type of harness you are using, whether the sensors are case grounded or isolated grounded. Here https://www.lt1swap.com/vortec_o2_sensors.htm is some info about that. I'm thinking that they may be losing ground somehow when you are slamming on the brakes. I know it's far fetched, but may give you something to check out.

I believe I'm using the case grounded O2 sensors. It's possible. I'll check my grounds. Will be taking it to a car show this weekend, will see if it throws the codes.

[ralmo94]

You say that both O2 sensors are not functioning. What are they doing when not functioning? Flatlining at 450mv? You may be having a ground issue depending on what type of harness you are using, whether the sensors are case grounded or isolated grounded. Here https://www.lt1swap.com/vortec_o2_sensors.htm is some info about that. I'm thinking that they may be losing ground somehow when you are slamming on the brakes. I know it's far fetched, but may give you something to check out.

I may be wrong, but as I understood his first post, the MIL CODE says they are not functioning, but he looked at Live Data, and it showed they WERE Functional

A data log of the issue would be a helpful as well.

[custodian]

The codes came back today, po134 and po154. Checked the live data and it showed around .450v for both sensors. These O2 senors were new and came with the setup, not sure of the brand name. All the wire harness and setup is for a 2002 1500 Silverado with the 5.3/4l60e 2wd.

UPDATE: This is what I've done so far. Checked my grounds, good, checked the O2 sensor wires and connections, good, I did find the exhaust down pipes had lost a nut on both sides and were loose on both sides. I'm using 10-15 Camaro exhaust and cat delete down pipes. I put four new bolts and fasteners on and have ordered new O2 sensors. When I drive it to the car show tomorrow, I'll be a watch out for any codes.

[Pulse_GTO]

The codes came back today, po134 and po154. Checked the live data and it showed around .450v for both sensors. These O2 senors were new and came with the setup, not sure of the brand name. All the wire harness and setup is for a 2002 1500 Silverado with the 5.3/4l60e 2wd.

UPDATE: This is what I've done so far. Checked my grounds, good, checked the O2 sensor wires and connections, good, I did find the exhaust down pipes had lost a nut on both sides and were loose on both sides. I'm using 10-15 Camaro exhaust and cat delete down pipes. I put four new bolts and fasteners on and have ordered new O2 sensors. When I drive it to the car show tomorrow, I'll be a watch out for any codes.

Any updates?

[custodian]

Any updates?

I did get one of the sensor codes after driving it to the car show. I was installing the new O2 sensors, and when I reached up to remove them I found they had come loose, was able to just use my hand to remove them. Went ahead and changed them and the new Denso sensors made it run like crap. One read .930v and the other one read .067v. I put the old ones back in and they read around .450v each. I fixed the exhaust connections, and have also installed new injectors. I broke a couple of the injector wires, came apart at the connector, and I'm waiting on all new connectors.

The truck runs great, just getting rid of the pesky codes is what's driving me nuts. I'll take some new readings when I get the new injector connectors installed.

[ralmo94]

Loose threads definitely could cause a bad signal path.

[custodian]

Loose threads definitely could cause a bad signal path.

Just like a bad connections in a wire.