Looking for a diagram to check wires

JEFFSORDYL

MEMBER
2005 BUICK ALLURE
3.8L
6 CYL
2WD
AUTOMATIC
148,000 MILES

Trying to back probe wires that connect to the starter control unit. The module itself is under the 3pack of coils I need a diagram to see where all the wires connect. Its called an ecm unit connector. Have a loose or cracked wire from that system. I changed both knock sensors and the car ran great for a week. Then check engine light came on. I used a plug in unit for checking all engine systems, it said front O2 sensor low voltage. Thank you!

1 Reply

AL514

MECHANIC
4,679 POSTS

Hello, Im not sure you need a Starter control unit, Heres the wiring diagrams for the front and rear Oxygen sensors circuits, There will be 2 wires at the front oxygen sensor that will be that will be the same colors, back probing those 2 wires should read 12volts, thats the oxygen sensor heater circuit, the oxygen sensor will not function if this voltage is missing. So check that first. This will be the oxygen sensor that is upstream of the Catalytic Converter. Verify there is no wire damage, such as sitting on the exhaust where it can melt. The 1st diagram is the top of the page, the 2nd is lower half.
If youre referring to the module under the ignition coils, that is not the ecm, that is the ignition control module.
The ecm (Engine control module) is inside the air filter housing.

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor

https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

Images (Click to make bigger)