DTC PZ2128, Loss Of Serial Communications - IRC: Testing
WARNING: This page is about a different car, the 1996 Cadillac Seville and 1996 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
Ensure IRC is operating properly. If IRC is not operating properly, diagnose and repair as necessary. If IRC is okay, check for poor connections at IRC. If connections are okay, replace IRC.