Skyhawk L4-112 18L Turbo Knock Sensor Component Information
Fig. 013 - Chart C-5 - Electronic Spark Control System Check.
1.
Road test procedure: Road test with engine at normal operating temperature, diagnostic terminal grounded and "SERVICE ENGINE SOON" light
flashing "Closed Loop." Note "SERVICE ENGINE SOON" light on normal to heavy acceleration from 30-40 MPH. If ESC is OK, the
"SERVICE ENGINE SOON" light will flash 5 times per second for 3 seconds.
Engine timing is higher than normal in the field service mode (diagnostic terminal grounded and engine running) assuring spark knock on
acceleration. A knock sensor that is OK will sense the knock and pull CKT 457 voltage low causing spark to retard. The ECM will respond and
flash the "SERVICE ENGINE SOON" light.