Code 54 and/or 74
WARNING: This page is about a different car, the 1988 Cadillac Seville and 1988 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.
Go to Chart A12 If no trouble is found while performing tests on Chart A12, do not go to chart F Instead go to Chart G Solenoid Valves. Perform solenoid valve test for rear valves. If no trouble is found, replace ECBM.