2000 Chevrolet Monte Carlo LS 3.4L no start mil lamp on

Car Question:

My neighbor's car died while being driven. Had it parked on the side of the road while waiting for the tow truck. Played with the ignition key (on and off) and suddenly the dash lights came on but then quit. Hooked up a pocket scanner but got no communication. How do you fix this?

ATS Adviser:

Before trying to fix this, check battery charge supply and connections. With these symptoms, the most likely problem is a wiring short caused by defective wires or modules. To check:

1.) Go to the DLC pin terminals on the left of the dash panel at the bottom and check pins 4/5. Probe these pins with a voltmeter and measure them against pin 16 as the power supply. You should get 12 volts. If not, the engine wiring is no good.

2.) Check pin 2 and looked for 5 volt signal voltage at key on engine off (KOEO). This wire is critical since it connects to all the bus modules of the engine like ECM, BCM, EBCM, Instrument cluster, etc. Best way to check is to hook up a voltmeter to this pin and verify if you have 5 volts. If not, unplug all the modules connected to this pin 2 wire at splice pack SP205 connector. It has a purple wire going to the pack and 9 different wires going out connected to each modules. You can tell which module is bad by disconnecting them one at a time and watch the voltage reading until you get 5 volts.

You will need a computer data line wiring diagram to be able to see all the modules and colors of the bus wires.

Check this approximate wiring diagram below for this problem. When testing the DLC, measure voltage at pin 2 for bus voltages. You will notice, there is only one bus wire going to each module.

You can get an exact wiring diagram from most parts stores if you ask for it when you buy the parts or join ATS.

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