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Code : P0643
Description : P0643 CADILLAC Sensor Reference Voltage ‘A’ Circuit High
Possible causes :
– Faulty Powertrain Control Module (PCM)
– Powertrain Control Module (PCM) harness is open or shorted
– Powertrain Control Module (PCM) circuit poor electrical connection
– Shorted sensor on 5 volt circuit
Solutions :
– Carry out a Reset via CarDiag
– Choose a better quality fuel
– Check that the tank cap is securely closed
– Check the oil level and add more if it is lower than MAX
– Restart an Automatic diagnostic via CarDiag
– If the fault persists, you can check the “Possible causes” listed above : visually inspect (by yourself (tutorials to come) or by a professional) the wiring harness and the associated connectors, check for damaged components, and look for broken, bent, pushed, or corroded connector pins.

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