Purpose
To determine electrical malfunctions detected by the ECM self-test and Output Circuit Check (OCC)
Tools
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
NOTE: If an EST is not available, see “Standard Test Using Cruise Switches” in Section 3 (page 72).
Procedure
1. Set parking brake to ensure the correct signal from the Electronic System Controller (ESC).
2. Turn the ignition switch to ON. (Do not crank engine.)
3. Select Diagnostics from the menu bar.
4. Select Key-On Engine-Off Tests from the drop down menu.
NOTE: When using the EST to do KOEO or KOER diagnostic tests, Standard Test is always selected and run first. If the ignition switch is not cycled, the Standard Test does not have to be run again.
5. From the KOEO Diagnostics menu, select Standard, then select Run to start the test.
The ECM will complete an internal self-test and an OCC. When the OCC is over, the DTC window will show DTCs, if there is a problem.
NOTE: This test takes less than 5 seconds.
While the test is running, the MasterDiagnostics® screen displays message Diagnostics Running .
6. Record all DTCs on Diagnostic Form. See “Diagnostic Trouble Codes” – Appendix C (page 643) for DTCs.
7. Correct problem causing active DTCs.
8. Clear DTCs.
Possible Causes
• Failed electrical components or circuitry
• OCC fault for the IPR valve or brake shut-off valve (if equipped)
• Inlet Air Heater (IAH)
— For initial calibrations, if the system voltage is less than 13 volts, DTC 251 may become active.
— Later calibrations and current hardware levels do not support DTC 251.
