ECU Issues
Thread Starter
Advanced
Joined: Dec 2017
Posts: 52
Likes: 3
From: Harahan LA
ECU Issues
I've had the car for almost 5 years now, and after finally installing Speed Engineering LT heads and catless X-pipe, which sound amazing) I knew I would finally have to spring for a tune. I brought the car to Mitch @ Tuned By Norm in Houma only to find out he can't tune it...for now.
My 2003 Zo6 has a cammed LS3 in it, and it seems the previous owner (builder) was having the same issues. The issue is the ECU is not reading the o2 sensors. So, he turned them off. Yeap (not a mistype), all four O2 sensors were turned off in the ECU.
The car's been running fine, other than loading up at idle. Above idle, it seems to work just fine.
Let's assume the O2 sensors I installed when I installed the headers are fine. I believe all it can be is either the harness, which I will check for continuity, or the ECU itself.
I've already found a diagram for the ECU plug and have identified the 2 upstream O2sensor positions on the plug.
My question is, if there's continuity in the wires, then how to I test the ECU? What value at the ECU should I be getting? for the upstream O2 sensors?
My 2003 Zo6 has a cammed LS3 in it, and it seems the previous owner (builder) was having the same issues. The issue is the ECU is not reading the o2 sensors. So, he turned them off. Yeap (not a mistype), all four O2 sensors were turned off in the ECU.
The car's been running fine, other than loading up at idle. Above idle, it seems to work just fine.
Let's assume the O2 sensors I installed when I installed the headers are fine. I believe all it can be is either the harness, which I will check for continuity, or the ECU itself.
I've already found a diagram for the ECU plug and have identified the 2 upstream O2sensor positions on the plug.
My question is, if there's continuity in the wires, then how to I test the ECU? What value at the ECU should I be getting? for the upstream O2 sensors?
Le Mans Master
Joined: Jul 2010
Posts: 5,923
Likes: 705
I've had the car for almost 5 years now, and after finally installing Speed Engineering LT heads and catless X-pipe, which sound amazing) I knew I would finally have to spring for a tune. I brought the car to Mitch @ Tuned By Norm in Houma only to find out he can't tune it...for now.
My 2003 Zo6 has a cammed LS3 in it, and it seems the previous owner (builder) was having the same issues. The issue is the ECU is not reading the o2 sensors. So, he turned them off. Yeap (not a mistype), all four O2 sensors were turned off in the ECU.
The car's been running fine, other than loading up at idle. Above idle, it seems to work just fine.
Let's assume the O2 sensors I installed when I installed the headers are fine. I believe all it can be is either the harness, which I will check for continuity, or the ECU itself.
just check your readings at the ECU plug
I've already found a diagram for the ECU plug and have identified the 2 upstream O2sensor positions on the plug.
My question is, if there's continuity in the wires, then how to I test the ECU? What value at the ECU should I be getting? for the upstream O2 sensors?
My 2003 Zo6 has a cammed LS3 in it, and it seems the previous owner (builder) was having the same issues. The issue is the ECU is not reading the o2 sensors. So, he turned them off. Yeap (not a mistype), all four O2 sensors were turned off in the ECU.
The car's been running fine, other than loading up at idle. Above idle, it seems to work just fine.
Let's assume the O2 sensors I installed when I installed the headers are fine. I believe all it can be is either the harness, which I will check for continuity, or the ECU itself.
just check your readings at the ECU plug
I've already found a diagram for the ECU plug and have identified the 2 upstream O2sensor positions on the plug.
My question is, if there's continuity in the wires, then how to I test the ECU? What value at the ECU should I be getting? for the upstream O2 sensors?
just check your readings at the ECU plug
Tech Contributor
Joined: Jan 2007
Posts: 19,115
Likes: 1,038
From: Dyer, IN
I've had the car for almost 5 years now, and after finally installing Speed Engineering LT heads and catless X-pipe, which sound amazing) I knew I would finally have to spring for a tune. I brought the car to Mitch @ Tuned By Norm in Houma only to find out he can't tune it...for now.
My 2003 Zo6 has a cammed LS3 in it, and it seems the previous owner (builder) was having the same issues. The issue is the ECU is not reading the o2 sensors. So, he turned them off. Yeap (not a mistype), all four O2 sensors were turned off in the ECU.
The car's been running fine, other than loading up at idle. Above idle, it seems to work just fine.
Let's assume the O2 sensors I installed when I installed the headers are fine. I believe all it can be is either the harness, which I will check for continuity, or the ECU itself.
I've already found a diagram for the ECU plug and have identified the 2 upstream O2sensor positions on the plug.
My question is, if there's continuity in the wires, then how to I test the ECU? What value at the ECU should I be getting? for the upstream O2 sensors?
My 2003 Zo6 has a cammed LS3 in it, and it seems the previous owner (builder) was having the same issues. The issue is the ECU is not reading the o2 sensors. So, he turned them off. Yeap (not a mistype), all four O2 sensors were turned off in the ECU.
The car's been running fine, other than loading up at idle. Above idle, it seems to work just fine.
Let's assume the O2 sensors I installed when I installed the headers are fine. I believe all it can be is either the harness, which I will check for continuity, or the ECU itself.
I've already found a diagram for the ECU plug and have identified the 2 upstream O2sensor positions on the plug.
My question is, if there's continuity in the wires, then how to I test the ECU? What value at the ECU should I be getting? for the upstream O2 sensors?
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,191
Likes: 3,874
From: Cape Coral, Florida
I've had the car for almost 5 years now, and after finally installing Speed Engineering LT heads and catless X-pipe, which sound amazing) I knew I would finally have to spring for a tune. I brought the car to Mitch @ Tuned By Norm in Houma only to find out he can't tune it...for now.
My 2003 Zo6 has a cammed LS3 in it, and it seems the previous owner (builder) was having the same issues. The issue is the ECU is not reading the o2 sensors. So, he turned them off. Yeap (not a mistype), all four O2 sensors were turned off in the ECU.
The car's been running fine, other than loading up at idle. Above idle, it seems to work just fine.
Let's assume the O2 sensors I installed when I installed the headers are fine. I believe all it can be is either the harness, which I will check for continuity, or the ECU itself.
I've already found a diagram for the ECU plug and have identified the 2 upstream O2sensor positions on the plug.
My question is, if there's continuity in the wires, then how to I test the ECU? What value at the ECU should I be getting? for the upstream O2 sensors?
My 2003 Zo6 has a cammed LS3 in it, and it seems the previous owner (builder) was having the same issues. The issue is the ECU is not reading the o2 sensors. So, he turned them off. Yeap (not a mistype), all four O2 sensors were turned off in the ECU.
The car's been running fine, other than loading up at idle. Above idle, it seems to work just fine.
Let's assume the O2 sensors I installed when I installed the headers are fine. I believe all it can be is either the harness, which I will check for continuity, or the ECU itself.
I've already found a diagram for the ECU plug and have identified the 2 upstream O2sensor positions on the plug.
My question is, if there's continuity in the wires, then how to I test the ECU? What value at the ECU should I be getting? for the upstream O2 sensors?
With a scan tool and with the O2 heater circuit fuse removed (fuse 15) you should see 450mv’s (O2 sensor bias voltage) key ON…if seeing 450 the wiring is fine…checking the O2 signal circuit is best tested with a LOW impedance DMM…whoever turned off all 4 O2 sensors is an idiot !!…he should NOT be tuning cars !!
Last edited by C5 Diag; Nov 2, 2025 at 02:35 PM.
