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Control module power supply: Diagnostics

If +30 or +15 is missing, the engine will not start and the system can not be contacted using the diagnostic tool.

Fig 1: Identifying Supply Circuit Diagram From Main Relay To Control Module

Courtesy of SAAB-SCANIA OF AMERICA, INC.

If the supply from the main relay to the control module is missing, diagnostic trouble code P1640 will be generated, the throttle will close and the engine will stop.