READING THE DIAGNOSTIC CODES - FLASH METHOD
The following steps describe the flash method to interpret diagnostic codes:
If you are here to begin diagnosis of a problem and already know how to read codes, as
well as understand active and inactive codes, refer to section 9.1.
1. Active versus Inactive codes:
[a] Active codes are the codes which are currently keeping the "Check or Stop Engine"
light on. Active codes are flashed via the Stop Engine Light (SEL).
[b] Inactive codes are all the codes previously logged in the ECM. These codes can be
cleared by using the DDR. Inactive codes are flashed via the Check Engine Light
The Diagnostic Request Switch reads codes on the CEL and SEL when an DDR is not
available. The following steps will enable you to obtain codes.
2. Turn vehicle ignition switch ON.
3. Depress and hold the diagnostic request switch.
[a] As an example, observe Code 13 (active) and Code 21 (inactive) flashing out on the
CEL and SEL; see Figure 5-1.
[b] If input used is SEO/Diagnostic Request, press and release the switch.
All information subject to change without notice.
6SE497 9709 Copyright © 1997 DETROIT DIESEL CORPORATION