Basic Diagnostic Procedure

Any diagnosis of the DEC system should be performed in the following order:

1. Ensure that all engine systems not related to the DEC system are operating properly. This should include a careful visual underhood inspection including: all vacuum hoses for correct routing, pinches, cuts, or disconnects; all wires in engine compartment for correct and good connections, burned or chaffed spots, pinched wires, or contact with sharp edges or hot exhaust manifolds.
2. Perform Diagnostic Circuit Check and continue diagnosis as indicated in chart. This check will either verify proper DEC system and ECM operation, or direct you to a specific trouble code chart(s) or another DEC system chart.
3. If any trouble codes are stored, start with the lowest numbered code and diagnose using the appropriate trouble code chart. If code 51, 52 or 53 are stored, always go to that chart FIRST.
4. After any repair to the DEC system, the Diagnostic Circuit Check must be repeated to verify proper system operation.