Conditions for Setting the DTC
WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
A DTC B1507 or 1508 will set when the load control circuit does not react as commanded. A DTC B1507 will set if the BCM enables the control circuit and the output does not react within 400 ms. A DTC B1508 will set if the BCM disables the control circuit and the output does not react within 400 ms.