| 0 | PRELIMINARY CHECKS | All OK | Problems encountered | Operation |
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| Check that the engine wiring negative lead is correctly fastened to earth and that the negative battery lead and all the cables are connected | Move on to Step 1 | Fastenings slack or oxidized | Continue as described by the diagnostic equipment. |
| 1 | CHECK USING DIAGNOSTIC EQUIPMENT | All OK | Problems encountered | Operation |
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| Using the Examiner check, in the Engine management control unit ambient, that there are no errors. | Move on to Step 2 | Errors present. | Continue as described by the diagnostic equipment. |
| 2 | CONTROL UNIT POWER SUPPLY CHECK | All OK | Problems encountered | Operation |
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| - Check that the power supply for the heater plugs control unit is correct;- Check the continuity of the heater plugs control unit (power) supply fuse;- Check the continuity of the control cable from the engine management control unit to the heater plugs control unit;- Check the continuity of the return cable from the heater plugs control unit to the engine management control unit See E5050 DIESEL ENGINES ELECTRONIC MANAGEMENT | Move on to Step 3 | 1. Power supply interrupted.2. Fuse blown3. Wiring between engine management control unit and heater plugs control unit interrupted. | 1. Restore correct power supply.2. Renew fuse after having identified the cause of the break.3. Restore the correct wiring. |
| 3 | HEATER PLUGS OPERATION CHECK | All OK | Problems encountered | Operation |
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| Check that the glow plugs are working properly. See Test 5520CA GLOW HEATER PLUGS OPERATION CHECK | Move on to Step 4 | 1. Resistance values above or below set limits.2. No supply for heater plugs | 1. Replace the glow plugs2. Replace the preheating control unit Op. 5520C20 HEATER PLUGS CONTROL UNIT - R.R |
| 4 | HEATER PLUGS CONTROL UNIT ACTIVATION CHECK | All OK | Problems encountered | Operation |
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| Check that the heater plugs control unit activation signal is correct. See Test | Move on to Step 5 | 1. Heater plugs control unit activation signal wiring interrupted.2. Engine management control unit defective. | 1. Restore the correct connection.2. Replace the engine management control unit Op. 1060G80 DIESEL ELECTRONIC INJECTION CONTROL UNIT - R.R |
| 5 | SIGNAL CHECK | All OK | Problems encountered | Operation |
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| Check the return signal from the heater plugs control unit to the engine management control unit. See T GLOW HEATER PLUG CONTROL UNIT OPERATION CHECK | End of diagnosis. | Signal not correct. | Replace the preheating control unit Op. 5520C20 HEATER PLUGS CONTROL UNIT - R.R |
