Chart A-2 Engine Control System Fault Telltale On No Codes

DESCRIPTION
The "Engine Control System Fault" lamp is powered through the Instrument Panel Cluster (IPC) and grounded by ECM Pin A19 to illuminate. The ECS telltale will bulb check at key on, is illuminated steadily during cranking and is illuminated whenever a tr9uble code with Service Now or Service Soon message is set.
ECM Pin A19 is turned on in conjunction with a code with Service Now or Service Soon message. If a trouble code is set, the ECM will send a Service Now or Service Soon status to the BCM over the UART data link. At the same time, the ECM grounds Pin A19 to turn on the "ENGINE CONTROL SYSTEM FAULT" telltale.
The "Engine Control System Fault" telltale will flicker when Pin "A" and Pin "B" of the ALDL connector are jumpered together to enter set timing mode. (In set timing mode the message "Set Timing" will be displayed on the Computer Control Driver Information Center (CCDIC).)

Notes on Chart A-2
1. Loose grounds or intermittent power connections can cause the ECM to repeatedly power-up then power-down or to "reset."
2. Checking for bulb grounded by ECM through Pin A19, or through a circuit fault.
3. Remove and replace both ECM connectors and ensure that they are latched. Check the MEM-CAL for proper orientation, pins bent, fully seated in the socket. Substitute a test MEM-CAL to see if the MEM-CAL is causing the light to flicker. If the test MEM-CAL does not correct the condition, replace the ECM. Be sure to perform "ECM Replacement Check", Chart C-1 in System Charts. The ECM may be damaged due to electrical overload from a low resistance component. Testing and Inspection