TESTING THE DDEC III SYSTEM (Cont'd.)
C. READING THE DIAGNOSTIC CODES - FLASH METHOD
NOTE: If you have turned here to begin diagnosis of a problem and already know how to read codes, as well as
understand active and inactive codes, turn to the first chart (labeled START) on page 3-345.41.
Active vs. Inactive Codes:
DDEC Ill makes use of both types of codes. As their names imply, the difference between the two are as follows:
Active Codes - These are the codes which are currently keeping the "Check or Stop Engine" light on.
Active codes are flashed via the Stop Engine light.
Inactive Codes These are all the codes logged in the ECM (whether or not they are currently turning on the
"Stop or Check Engine" light). These codes can be cleared by using the Diagnostic Data Reader. Inactive
codes are flashed via the Check Engine Light.
Using the Diagnostic Request Switch
This Troubleshooting Guide is intended to be used with a Diagnostic Data Reader (DDR). In most Instances, only the
DDR can provide the information necessary for a quick diagnosis of the problem. Should you just need to read out codes,
however, and not have a DDR available, the following procedure will let you read out codes on the CEL and SEL:
Turn ignition on.
Depress and hold the diagnostic request switch.
Observe the codes flashing out on the CEL and SEL. Example: Code 13 (active) and 21 (Inactive) below.
RED - SEL
YELLOW - CEL
This will continue as long as the diagnostic request switch is held with the ignition on
Change 3 3-345.15