Chart A-1 No Service Engine Soon Light

Chart A-1 - No "Service Engine Soon" Light:

Wiring Diagram for No "Service Engine Soon" Light.:

CHART A-1
NO - SERVICE ENGINE SOON" LIGHT


Circuit Description:


There should always be a steady "Service Engine Soon" (SES) light when the ignition is "ON" and engine stopped. The engine control module (ECM) will turn the light "ON" by grounding CKT 419 at the ECM. Engine runs OK, check:
Faulty light bulb CKT 419 open Gage fuse blown. This will result in no oil or generator lights, seat belt reminder, etc. Engine cranks, but will not run. Continuous battery fuse or fusible link open ECM ignition fuse open Battery CKT 240 to ECM open Ignition CKT 439 to ECM open Poor connection to ECM


Test Description: Numbers below refer to circled numbers on the diagnostic chart.
1. Probing CKT 419 to ground creates an alternate ground. If the "service engine soon" (SES) light comes "ON," this verifies that the trouble is not in the lamp portion of the circuit.
2. Solenoids and relays are turned "ON" and "OFF" by the ECM, using internal electronic switches called "drivers." Each driver is part of a group of four called quad-drivers.
Before replacing ECM, be sure to check the coil resistance of all solenoids and relays controlled by the ECM. See ECM wiring diagram for the solenoid(s) and relay(s) and the coil terminal identification. When checking Transmission/Transaxle Converter Clutch (TCC) solenoid, be sure to raise drive wheels and run above 30 mph to close third gear apply switch.