Code 52 - Back-Up Power Supply Fault: Description

Back-up power supply is contained within diagnostic monitor. Power supply consists of 4 capacitors and a voltage boost circuit. Voltage boost circuit charges capacitors to 16-19 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) resistance 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 16 volts after about 45 seconds, Code 52 will set.