Power Supply: Notes

Fig 1: Identifying Power Supply System

KL30 - Battery Voltage:  It supplies the operating voltage to the ECM. The ECM contains a "EEPROM" that will store data in the event of power loss (battery disconnected).

KL15 - Ignition Switch:  When the ignition is switched "on" the ECM is informed that the engine is about to be started. KL15 also supplies voltage to the Engine Control Module Relay. Switching KL15 "off" removes the ECM operating voltage.

Engine Control Module Relay:  It provides the operating voltage for:

• ECM 
• Fuel Injectors 
• Idle Speed Valve 
• Evaporative Emission Valve/Air Inlet Shut Off Valve 
• Exhaust Flap Solenoid 
• VANOS Solenoid 
• Running Losses Solenoid 

1. Fuel Pump Relay 
2. Oxygen Sensor Heating 
3. EGS (and ASC on E39) 
4. Hot Film Air Mass Sensor 
5. Secondary Air Pump Relay 
6. Secondary Air Injection Solenoid 

Ground:  Multiple ground paths are necessary to complete current flow through the ECM. The ECM ground pin numbers and functions are:

• Pin #
• Ground
• 04, 28, 32, 34, 56
• ECM
• 07
• Hot Film Air Mass Sensor
• 38
• Knock Sensor Shielding
• 39
• Temperature Sensors
• 40
• Crankshaft Position/RPM sensor and Fuel Tank Pressure Sensor
• 41, 64
• Camshaft Position Sensors Shielding
• 42
• Throttle Position Sensor