Code 52 - Back-Up Power Supply Fault: Description
WARNING: This page is about a different car, the 1995 Ford Pickup, 1995 Ford F-Super Duty, 1995 Ford Cab & Chassis, and 1995 Ford Bronco. However, it is still accessible from the selected car via links, so may be relevant.
Back-up power supply is contained within diagnostic monitor. Power supply consists of a capacitor and a voltage boost circuit. Voltage boost circuit charges capacitor to 23-25 volts when ignition is on. Back-up power supply is connected through a diode to diagnostic monitor terminal No. 15 (circuit No. 611). Resistance of circuit No. 611 should be infinite (open) to ground. This open circuit allows capacitor to maintain its higher voltage because there is no discharge path for capacitor. If voltage on capacitors does not reach and maintain a minimum of 23 volts after about 45 seconds, Code 52 will set.