Chart A1 - No "SES" Light (5.0/5.7L): Notes

There should always be a steady "SERVICE ENGINE SOON" ("SES") light with ignition on and engine stopped. Battery is supplied directly to the light bulb. The ECM controls the light and turns it on by providing a ground path through circuit No. 419 to the ECM.

1. This test will determine if the ECM has the ability to ground circuit No. 419.
2. If both the continuous battery supply voltages are lost at terminals "B1" and "C16" or the ignition feed to terminal "A6" is not present, the "SERVICE ENGINE SOON" light will not come on with the ignition on.