Circuit/System Description
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The engine control module (ECM) has 3 internal 5 V reference busses called 5 V reference 1, 5 V reference 2, and 5 V reference 3. Each reference bus provides 5 V reference circuits for more than one sensor. Therefore, a fault condition on one 5 V reference circuit will affect the other 5 V reference circuits connected to that reference bus. The ECM monitors the voltage on the 5 V reference busses.