The PCM monitors ignition voltage on circuit 439 at all times with reference to circuit 551 (ground) when the engine is running. Ignition voltage from circuit 439 can be read on the scan tool as IGNITION 1 voltage. DTC P0562 sets when the PCM detects low system voltage. DTC P0563 sets when the PCM detects high system voltage. These values are out of the normal charging system voltage range.

DTC P0563 will set if ignition voltage is greater than 17 volts when:

DTC P0562 and P0563 diagnostics run continuously with the engine running.

DTC P0562 and P0563 are type D DTCs.

Important: DTC P1635 will NOT set if a short to B+ on the 5-volt reference circuit occurs on vehicles built prior to VIN 1Z200000.

If DTC P1635 is set, diagnose that DTC first. A short to ground on one of the 5-volt reference circuits (EGR position sensor, fuel tank pressure sensor, MAP sensor, or TP sensor) may set DTC P0562 and/or P0563. A short to B+ on one of the 5-volt reference circuits may set DTC P0561 and/or P0562.

If DTC P0621 is set, diagnose that DTC first. A generator L-terminal low voltage circuit fault will cause the generator not to charge.

An open or intermittent open in generator L-terminal circuit 25 will cause the generator not to charge. DTC P0562 will set when battery voltage falls below the calibrated voltage.

Jump starting another vehicle with a dead battery may cause large voltage fluctuations and may set P0562 or P0563.

To locate an intermittent problem, use the scan tool to monitor IGNITION 1 voltage with the engine running. With all accessories ON or all accessories OFF, voltage should be in the range of 11-17 volts.

With the engine OFF, compare IGNITION 1 voltage on the scan tool with actual battery voltage with a DVOM. If readings do not fall within +/-0.2 volts, check circuit 439 and 551 for corrosion and tightness.

Perform a charging system test. Refer to Charging System Test .