CAMSHAFT AS 1240453 - Caterpillar

System Operation Description:The EIS Control Module will take action in order to help protect the engine from detonation. The control module will attempt to stop the detonation by retarding the ignition timing. If this effort is unsuccessful and the detonation continues at severe levels, the control module will signal for an engine shutdown.The detonation sensors provide an electrical signal of the mechanical engine vibrations to the control module. The control module monitors the detonation sensors in order to determine the severity of the detonation.
Illustration 1 g00664930
Typical display of the level of detonation on the Digital Diagnostic Tool (DDT)Three bars of detonation are shown.If detonation occurs, the control module will perform the following actions:
Continuously illuminate the "" lamp.
Activate a 326-01 diagnostic code.
Retard the ignition timing.The control module can retard the timing by as little as 0.1 degree for light detonation. The control module can retard the timing by a maximum of 6 degrees for severe detonation. If the date of the control module's software is earlier than October 1994, the control module can retard the timing by a maximum of 25 degrees for severe detonation.As the detonation level decreases, the control module will begin to advance the timing out of the detonation retarded timing. A proportional strategy is used to advance the timing. The rate of advance depends on the severity of the detonation. If the detonation level is low, the advance rate is faster. The fastest rate of timing advance out of detonation is two degrees per minute.If the ignition timing is fully retarded and severe detonation continues, the control module will perform these actions.
Continuously illuminate the "SHUTDOWN" lamp.
Activate a 325-01 diagnostic code.
Activate the "Shutdown Relay Output".Detonation can be caused by many different factors. Therefore, this procedure has many test steps. Usually, the root cause of detonation is identified early in the procedure.
Illustration 2 g01043894
Schematic diagram of the detonation sensors
Illustration 3 g01043896
Schematic diagram of the detonation sensorsThe engine is configured for Canadian Standards Association (CSA).Test Step 1. Check the TimingNote: The desired timing will vary for different engine applications.Use an electronic service tool to check the engine timing. For the correct desired timing for the engine application, refer to the appropriate Engine Performance, "Fuel Usage Guide".Expected Result:The desired timing is correct.Results:
OK - The timing is correct for the engine application. Proceed to Test Step 2.
Not OK - Detonation occurs because the timing is not correct for the engine application.Repair: Use an electronic service tool to set the proper timing. Verify that the original problem is resolved.STOPTest Step 2. Check the Air/Fuel RatioNote: The air/fuel ratio will vary for different engine applications.