viper 550 esp trouble

In 99, chevy made both the old body style, and the new body style trucks. Which do you have?

I have the new body style

Heres what I found. tach signal---white----at ignition coil or PCM "Ignition coil is located on passenger rear of engine. Some trucks will be equipped with a multi coil ignition system similar to the Corvette. Tach wire may be located at each coil or at the PCM-Left front of engine compartment" So if your truck is the newer body style, it uses the multi coil setup, if its the old style, the ign coil is on the passnger rear on the engine. Test the suspected tach wire with a digital multimeter. Set the meter to ac voltage, and groung the negative wire. Probe the suspected tach wire with the positive probe while the engine is running. Look at yer reading on the meter and have an assistant press the accelerator pedal to rev up the engine, you will see the reading increase with engine rpm's if you have the correct wire.