5-Volt Reference Circuit Error Diagnosis: Description
WARNING: This page is about a different car, the 2002 Saturn LW200, 2002 Saturn L200, and 2002 Saturn L100. However, it is still accessible from the selected car via links, so may be relevant.
One of 3 PCM 5-volt reference circuits provide reference voltage to A/C pressure sensor, fuel tank pressure sensor and throttle position sensor. Current for each 5-volt reference circuit flows through sensor ground, which is provided internal to PCM. PCM regulates 5-volt reference voltage to 5 volts under most operating conditions. This is necessary for accurate sensor information.