DDEC TROUBLESHOOTING
90.2.4
Check for +5 volts or Return Open
Perform the following steps to check for +5 volts or return open.
1. Turn vehicle ignition switch OFF.
2. Disconnect the engine harness connector at the ECM.
3. Install a jumper wire between sockets A and C of any sensor connector that reads less than
4.7 volts. Refer to section 90.2.2.
4. Measure resistance between sockets W1 and Y2 of the engine harness connector.
[a] If the resistance measurement is less than or equal to 5 , refer to section 90.2.5.
[b] If the resistance measurement is greater than 5 or open, either the engine +5 volt line
(#416), or the return line (#452) is open. Repair the open and refer to section 90.2.7.
90.2.5
Check for Short to Ground
Perform the following steps to check for short to ground.
1. Turn vehicle ignition switch OFF.
2. Remove jumper wire.
3. Measure resistance between sockets A and C of the sensor connector.
4. Measure resistance between socket C of the sensor connector and a good ground.
[a] If the resistance measurement for both readings is greater than 1,000 , or open,
refer to section 90.2.3.
[b] If either resistance measurement is less than or equal to 1,000 , the engine +5 volt
line (#416) is shorted to either the sensor return line (#452) or to chassis ground.
Repair the short and refer to section 90.2.7.
90.2.6
Check for Short to Battery
Perform the following steps to check for a short to battery.
1. Turn vehicle ignition switch OFF.
2. Remove both fuses to the ECM.
3. Disconnect all five connectors at the ECM.
4. Measure resistance between socket W1 on the engine harness connector and B3 on the
vehicle harness connector.
5. Measure resistance between socket W1 on the engine harness connector and the battery
(+).
[a] If the resistance measurement for both readings is greater than 1,000 , or open,
refer to section 90.2.3.
All information subject to change without notice.
6SE497 9709 Copyright © 1997 DETROIT DIESEL CORPORATION
90-5
