10.6
DIAGNOSTIC REQUEST SWITCH INOPERATIVE
10.6 DIAGNOSTIC REQUEST SWITCH INOPERATIVE
Before using this procedure, all basic mechanical checks and physical inspections should have
been performed with no problem found. Also the diagnosis of the DDEC system in Section 9
referred you to this section.
10.6.1
Check Diagnostic Request Circuit
Perform the following steps to check the diagnostic request circuit:
1. Turn ignition ON; engine not running.
2. Plug in DDR.
3. Select Switch/Light Status.
4. Depress and hold diagnostic request switch.
5. Observe the Diagnostic Request Status on the DDR.
[a] If the display reads ON, refer to section 10.6.2.
[b] If the display reads OFF, the diagnostic request line (#528) is open, or is not being
grounded when the switch is depressed. Check the #528 wire and ground for
diagnostic request switch. Repair the problem; refer to section 10.6.4.
[c] If no diagnostic request on the DDR input list, the ECM is not configured for
diagnostic request operation. Refer to the DDEC Application and Installation
manual, 7SA800.
10.6.2
Check Stop Engine Light and Check Engine Light Bulbs
Perform the following steps to check the SEL and CEL bulbs:
1. Turn ignition OFF.
2. Remove CEL and SEL bulbs. Check to see if either is burned out or damaged.
[a] If the bulbs are okay, refer to section 10.6.3.
[b] If the bulbs are defective, replace the bulbs. Refer to section 10.6.4.
10.6.3
Check 12 / 24V Ignition Line
Perform the following steps to check the 12/24V ignition line:
1. Turn ignition ON.
2. Disconnect vehicle harness connector at ECM.
3. Measure voltage at cavity B3 (#439).
[a] If voltage measurement is less than 11.5V, the 5 amp fuse or circuit breaker is blown,
and the ignition line could be open or shorted to ground.
All information subject to change without notice.
10-26
6SE497 9709 Copyright © 1997 DETROIT DIESEL CORPORATION
