There isn't a dedicated "interior light timer relay" in the traditional sense on a 2006 Chevy Express van. The interior light timing function is controlled by the Body Control Module (BCM). The BCM is a computer that manages various electrical functions, including the timed delay for the interior lights. It doesn't use a separate relay for this specific task.
Therefore, you won't find a separate relay to replace or troubleshoot. Any issues with the interior light timer would require diagnostics of the BCM itself, potentially involving a scan tool to check for fault codes.
