Can some one explain me how the circuit works & how ecu detects whether lamp is present or not

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put on hold as unclear what you're asking by Transistor, Kevin Reid, Blup1980, laptop2d, Elliot Alderson Jan 12 at 2:11

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    \$\begingroup\$ What makes you think the ECU "senses the lamp"? How could the ECU turn on the lamp to tell you that a fault is detected if the fault is a missing lamp? \$\endgroup\$ – Elliot Alderson Jan 11 at 16:44
  • \$\begingroup\$ becoz the same ecu pin is connected to 2nd ecu for detection. (If any fault is detected the ecu switches the low side and the lamp gets ON) info mentioned in bracket tells how system works actually if no lamp in the ckt system cannot throw warning \$\endgroup\$ – Yuvaraj Jan 11 at 17:24
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    \$\begingroup\$ Your question reads as though there is a fault lamp that turns on when there is a fault in the fault lamp. I am voting to "close as unclear". There is an edit link under your question so that you can improve it. There is a schematic button on the editor toolbar so you can add a diagram. Welcome to EE.SE. \$\endgroup\$ – Transistor Jan 11 at 17:41
  • \$\begingroup\$ The ECU can detect a missing/failed open lamp by the absence of 24 Volt on the pin controlling the lamp. A short-circuited lamp can be detected by monitoring the current into that pin. Either when the lamp is turned on, or with a small detection current allowed to flow while the lamp is off. \$\endgroup\$ – JimmyB Jan 13 at 15:04
  • \$\begingroup\$ Thanks for sharing the information. \$\endgroup\$ – Yuvaraj 2 days ago

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