TEE ASSEM. 5K2493 - Caterpillar

System Operation Description:The Timing Control Module (TCM) will take action in order to help protect the engine from detonation. The TCM will attempt to stop the detonation by retarding the ignition timing. If this effort is unsuccessful and the detonation continues at severe levels, the TCM will signal for an engine shutdown.The detonation sensors provide an electrical signal of the mechanical engine vibrations to the TCM. The TCM monitors the detonation sensors in order to determine the severity of the detonation.The detonation protection is disabled for engine speeds that are less than 500 rpm. Detonation protection is enabled ten seconds after the engine reaches 500 rpm.
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Typical display of menu 2 and screen 12 on the DDTThree bars of detonation are shown.The retardation of timing is the first level of protection against detonation. If the engine detonation is greater than five bars, the TCM retards the ignition timing by six degrees. The control begins checking the detonation for a possible shutdown after the TCM has retarded the timing. There are two strategies for a shutdown due to detonation. One strategy is for non-gallery cooled pistons. The second strategy is for gallery cooled pistons.For non-gallery cooled pistons, a shutdown will be activated if detonation exceeds six bars within five seconds after the engine has been retarded. A shutdown will also be activated if detonation is in the range of five to six bars after the five seconds.For gallery cooled pistons, detonation is not checked for the first six seconds after the timing is retarded. A shutdown will be activated only if both of the following conditions are true:
The detonation level is in the range of five to six bars.
The engine has been retarded for six seconds.As the detonation level decreases, the TCM will begin to advance the timing out of the detonation retarded timing. The maximum rate of advance is one degree per minute. This rate is achieved for detonation levels of two to three bars. If the detonation level increases to a level of four to five bars, the rate of the advance will decrease or the advance will stop.While the ignition timing is retarded due to detonation, the yellow "DETONATION RETARDED TIMING" LED will be illuminated.
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Not all of the Test Steps for determining the cause of detonation follow a linear sequence. The results of the steps determine the sequence of the steps. Illustrations 3 through 8 constitute a flow chart of the Test Steps. Use the Illustrations only for reference. To determine the cause of detonation, use the more detailed instructions that are included in the Test Steps which follow the Illustrations.
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Test Step 1. Check the Timing.Note: The desired timing will vary for different engine applications.Use the DDT to check the engine timing. For the correct desired timing for the engine application, see Systems Operation/Testing and Adjusting, SENR4604, "Ignition System".Expected Result:The desired timing is correct.Results:
OK - The timing is correct for the engine application. Proceed to test step 2.
Not OK