Originally Posted by almikyska
How would i hook up a fair fuel ratio gauge?
They typically are electric with three wires. A +12VDC (ignition circuit, on with key in Run), a engine sensor ground, and a signal wire from the O2 sensor.
You can connect all of them at the ECM. The connections should be soldered in order to get a good read from the O2 sensor.
The ignition comes from the Black connector block (cavity A6, Pink wire with a black stripe)
O2 Signal can be connected at the yellow connector block (cavity D2, should have Black with Purple stripe wire.)
O2 Ground can be connected at the yellow connector block (cavity D3, should have a tan wire in it.)
This will put your A/F gauge in parallel to the ECM'* own O2 sensor connections...you will see the same values the ECM is seeing.
Last caveat to all this: GM does not use a wide-band O2 sensor. The O2 sensor also lags behind the engine and is erratic at less than WOT, go it'* usefulness is for checking rich/lean when you stomp on the throttle and hold it down.