HOW TO USE THIS BOOK
Sections 2 (Basic Knowledge Required) and 3 (Testing the DDEC II System) should be read and understood completely.
If basic mechanical checks have been made, no trouble was found, and the problem is now believed to be in the
DDEC II System, turn to Section 4- Troubleshooting Charts. Always start with the first Chart (Iabelled START) on Page
3-121. If a Diagnostic Data Reader (DDR) is not available, the chart Iabelled CEL (Check Engine Light) can be used.
Use the charts to pinpoint the problem and perform repairs. The charts are in a three-column format. The first column
lists the test steps- to perform and in what sequence to perform them. The second column gives the list of possible
results you may obtain, based on the steps performed. The third column indicates what to do next, based on your result.
WHAT TO DO NEXT
C2-9 Check ECM
l Turn ignition off.
l Disconnect all connectors at the
l Check terminals at all ECM
connectors (both the ECM and
harness side) for damage,
corrosion and unseated pins or
The charts will always instruct you to clear the codes after all repair work is done, and confirm the repair (typically by
running the engine and checking if the codes and/or symptoms have returned).
Assistance may be required during performance of certain tasks.