28.3
TROUBLESHOOTING FLASH CODE 28
3. Start engine and run until Check Engine light comes on, or for eight minutes.
4. With engine still running, read active codes.
[a] If code 172/4 and any other codes were logged, refer to section 28.3.4.
[b] If flash 172/3 and any other codes except 172/4 were logged, refer to section 28.3.3.
28.3.3
Check Air Temperature Sensor Connectors
Perform the following steps to check the ATS connector.
1. Check terminals at the ATS connector (both sensor and harness side) for damage; bent,
corroded and unseated pins or sockets.
[a] If terminals and connectors are not damaged, replace ATS. Refer to section 28.3.6.
[b] If terminals and connectors are damaged, repair/replace wires and
refer to section 28.3.6.
28.3.4
Check for Short
Perform the following steps to check for a short.
1. Turn the ignition OFF.
2. Disconnect the engine harness connector at the ECM.
3. Measure resistance between sockets N2 and Y2 on the engine harness connector.
See Figure 28-3.
4. Measure resistance between socket N2 and a good ground.
[a] If the resistance measurement between sockets N2 and Y2 and between socket N2
and a good ground is greater than 10
or open, refer to section 28.3.5.
All information subject to change without notice.
28-6
6SE497 9709 Copyright © 1997 DETROIT DIESEL CORPORATION
