DTC B1372: Device Ignition No. 1 Circuit Low

1. Turn ignition on. Using scan tool, select BCM SECURITY DATA DISPLAY, IGNITION 1 state. If IGNITION 1 state does not display HIGH, go to next step. If IGNITION 1 state displays HIGH, problem is intermittent. Check for poor connection to BCM. See COMPONENT LOCATIONS . Repair as necessary and retest operation.
2. Check BCM/ECM/CRUISE/ABS fuse (10-amp), located in underhood fuse block. See COMPONENT LOCATIONS . If fuse is okay, go to next step. If fuse is blown, repair short to ground in Pink wire between BCM/ECM/CRUISE/ABS fuse and Gray 24-pin BCM connector J2 terminal A10. See Fig 1. See WIRING DIAGRAMS . Replace BCM/ECM/CRUISE/ABS fuse and retest operation.
3. Ensure ignition is on. Connect DVOM (backprobe) between ground and Gray 24-pin BCM connector J2 terminal A10 (Pink wire). See Fig 1. See WIRING DIAGRAMS . If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Pink wire between BCM/ECM/CRUISE/ABS fuse and Gray 24-pin BCM connector J2 terminal A10. Retest operation.
4. Check for poor connection to BCM. Repair as necessary and retest operation. If BCM connection checks okay, replace BCM. See BODY CONTROL MODULE  under REMOVAL & INSTALLATION. Retest operation.

Fig 1: Identifying Pink & Gray 24-Pin BCM Connectors

Courtesy of GENERAL MOTORS CORP.