DTC P1530: Ignition Timing Adjustment Switch Circuit Malfunction: Description
WARNING: This page is about a different car, the 2002 Suzuki Esteem. However, it is still accessible from the selected car via links, so may be relevant.
Ignition timing test switch terminal is located in the DIAG.-1 test connector. Connector is located in engine compartment fuse/relay block located at left side of engine compartment. When appropriate terminal is grounded, ECM resets ignition timing to initial one.