You can ground the lead in the right tool box and read the codes by how many times the lights blink when you turn the ignition on.
On the G5 it's under the seat. Right on the connector that plugs into the ECU.
Here's the codes,
MIL BLINK CONTENT
Engine will start but not perform to its potential. MIL will glow continuous
LONG 0 SHORT 6 Throttle Position Sensor (TPS) circuit malfunctioning
LONG 0 SHORT 9 Manifold Absolute Pressure (MAP) circuit malfunctioning
LONG 1 SHORT 1 Engine oil Temperature (TE) circuit malfunctioning
LONG 1 SHORT 7 O2 Sensor circuit malfunctioning
LONG 4 SHORT 5 O2 Sensor heater circuit malfunctioning
Engine will NOT Start but will crank. MIL will glow continuous
LONG 1 SHORT 5 Rollover Sensor circuit malfunctioning
LONG 3 SHORT 3 Injector circuit malfunctioning
LONG 3 SHORT 7 Ignition Coil circuit malfunctioning
LONG 4 SHORT 1 Fuel Pump circuit malfunctioning
LONG 6 SHORT 6 Crankshaft position circuit malfunctioning
Testing Procedure using the Test pin in the vehicle