Conditions For Running DTC

WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 2003 Hummer H2, 2003 GMC Yukon XL, 2003 GMC Yukon, 2003 GMC Sierra, and 2003 GMC Cab & Chassis Sierra. However, it is still accessible from the selected car via links, so may be relevant.

DTC P1518 is not set.
The ignition switch is in the crank or run position.
The ignition voltage is greater than 6 volts.