Vehicle: 2009 GMC Acadia, FWD, V6-3.6L, automatic transmission/transaxle
Mileage: 88,720
Problem: The Acadia was towed to the shop for a no-start/does not crank concern.
Case details: The technician attempted to scan for diagnostic trouble codes (DTCs) but found no communication with the engine control module (ECM). He checked for battery power to the ECM. There was none. The technician found that the ECM1 fuse (15A) was blown. He replaced the fuse, but as soon as he turned the ignition key to the "on" position, the fuse blew again.
Using the factory wiring diagram in ALLDATA as a guide, he found the only power supply to the ECM1 fuse was from the ECM itself. He unplugged the ECM and replaced the fuse. This time, turning the ignition switch to the "on" position did not blow the fuse. He load-tested the circuits, between the ECM and ECM1 fuse. They all passed. He determined that the ECM must have been shorted internally.
Confirmed repair: The technician replaced and programmed the ECM. After that, the Acadia cranked, started and ran great… and the ECM communicated normally. Problem solved!
Reprinted with permission from ALLDATA.
