Circuit/System Description

The engine control module (ECM) has 2 internal 5-volt reference busses called 5-volt reference 1 and 5-volt reference 2. Each reference buss provides 5-volt reference circuits for more than one sensor. A fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to that reference buss. The ECM monitors the voltage on the 5-volt reference buss.

The 5-volt reference 1 buss provides 5 volts to the following sensors:

• The manifold absolute pressure (MAP) sensor
• The fuel tank pressure (FTP) sensor
• The air conditioning (A/C) refrigerant pressure sensor
• The accelerator pedal position (APP) sensor 2
• The exhaust camshaft position (CMP) sensor
• The intake CMP sensor

The 5-volt reference 2 buss provides 5 volts to the following sensors:

• The APP sensor 1
• The throttle position (TP) sensor 1 and 2
• The crankshaft position (CKP) sensor
• The secondary air injection (AIR) pressure sensor