DTC C1215: Idle Up Circuit Faulty: DTC Detecting Condition
WARNING: This page is about a different car, the 2003 Suzuki Vitara. However, it is still accessible from the selected car via links, so may be relevant.
DTC C1215 can be set anytime EBCM requests normal idle speed and the voltage on idle up circuit is less than 3.5 V. DTC C1215 can also be set if EBCM requests an increase in idle speed (idle up) and voltage on the idle up request circuit is greater than 4.0 V.