HOW TO USE THIS BOOK
Sections 2 (Basic Knowledge Required) and 3 (Testing the DDEC III System) should be read and understood
If basic mechanical checks have been made, no trouble was found, and the problem is now believed to be in
the DDEC III System, turn to Section 4 - Troubleshooting Charts. Always start with the first Chart (labeled START)
on Page 3-345.41. If a Diagnostic Data Reader (DDR) is not available, the chart labeled 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 results.
WHAT TO DO NEXT
C2-9 Check ECM
Turn ignition off.
Reprogram ECM. Then go to
connectors are okay.
Disconnect all connectors at the
Check terminals at all ECM
Then go to C2-30.
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).
Change 3 3-345.5