TESTING THE DDEC II SYSTEM (Contd.)
2. Using the Check Engine Light (CEL)
This Troubleshooting Guide is intended to be used with a Diagnostic Data Reader. In certain instances, only
the Reader can provide the information necessary for quick diagnosis of the problem. Should you just need to
read out codes, however, and not have a Reader available. the following procedure will let you read
out codes on the CEL:
a. Turn ignition off.
b. Jumper pin A to pin M on the 12 pin, DDL connector (typically located in the cab).
c. Turn ignition on and observe the codes flashing out on the CEL. Example: Code 13 and 21.
This will continue as long as the pins are jumpered with the ignition on.