Circuit/System Description

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

The 5 V reference 1 buss provides 5 V 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 brake fluid pressure sensor

The 5 V reference 2 buss provides 5 V to the following sensors:

• The APP sensor 1
• The throttle position (TP) sensor 1 and 2
• The crankshaft position (CKP) sensor
• The brake booster vacuum sensor