TM-9-2320-361-24-1 Field Maintenance Manual Volume 1 for M44A2 Series Trucks
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TM 9-2320-361-24-1 0017 00 0017 00-1 FIELD TROUBLESHOOTING 2-1/2 TON, 6X6, M44A2 SERIES TRUCKS (MULTIFUEL) SIMPLIFIED TEST EQUIPMENT FOR INTERNAL COMBUSTION ENGINE—REPROGRAMMABLE (STE/ICE-R) GO CHAIN TROUBLESHOOTING INTRODUCTION, TEST DESCRIPTIONS, AND GO CHAIN FLOWCHARTS INTRODUCTION To troubleshoot a vehicle problem, the technician uses the Vehicle Test Meter (VTM), transducers, test leads, and vehicle test cards. The VTM performs tests based upon the numbers the technician places in TEST SELECT switches. When the technician dials in the numbers and presses the TEST button, on the VTM, the test is initiated. For some tests, an offset test is required before the test can be performed. To initiate an offset test, the technician dials in a set of assigned numbers for the required test, presses and holds in the TEST button for several seconds. TEST DESCRIPTIONS Offset Test The offset test voids characteristic differences between the VTM, test leads, and transducers and also zeros the meters. Once the offset test is performed, the VTM automatically corrects for offsets before displaying measured values. Displayed offset values should be compared to limits on the vehicle test card for the test being performed. If the displayed value is not within limits that are listed on the test card then either the transducer or cable needs to be replaced. The offset test is performed with a test probe, cable, or transducer connected to the VTM. Care should be taken to see that no stimulus is applied to the transducer. To perform an offset test, dial test number into the TEST SELECT switches. Press and hold the TEST button until prompting message CAL appears on the display. In a few seconds after release of the TEST button, a number will appear.This is a measured offset value associated with the test probe cable or transducer and cable. Control Tests Introduction Control tests are used to change (or control) the way a vehicle test is displayed, or the way it is run. There are five (5) control tests: 01 Interleave (displays RPM with next test). 04 Display peak-to-peak value for next test. 02 Display minimum value for next test. 05 Initiate full power simulation. 03 Display maximum value for next test. Control tests 01, 02, 03, and 04 specify action to be taken by the next test only. A subsequent test will reset the control. Control Test 1 Interleave test (Test 01) alternately measures engine speed and a second parameter such as fuel pressure or alternator voltage. To initiate interleave, dial 01 into TEST SELECT switches and press and release the TEST button. The prompting message PASS will signal the technician to dial in a second test number and again press and release TEST button. Control Test 2 Minimum Value Test, (Test 02), displays minimum value measured during a test.To initiate a minimum value display, dial 02 into TEST SELECT switches and press and release TEST button. The prompting message PASS will signal the technician to dial in desired test number and again press and release TEST button. The minimum value is displayed and updated whenever a lower minimum value is measured. Entering 02 and test number again will reset process and a new minimum value will be displayed.