P0562 Battery/System voltage low

P0562 Code - The Electronic Voltage Regulation (EVR) system maintains the system voltage at a desired by turning the Pulse Width Modulation (PWM) Alternator Field Control circuit (A) on and off.

When the Alternator field is turned on, the system voltage increases. When the Alternator field is turned off, the system voltage slowly drops. The rate at which this happens is dependent upon the existing electrical loads, ambient under hood temperature, and the engine speed. A constant system voltage (D,C,B) can be maintained only when the Alternator field is switched on and off at a duty cycle that very accurately emulates the existing electrical loads given the existing ambient under hood temperature and engine speed.

During normal operation, the voltage reading at the Alternator output stud be very close to the target charging voltage viewed on the scan tool. This is the system voltage and is sensed by the PCM through the Fused B+ circuit (B). With the Alternator connector plugged in, and back probing the Alternator sense circuit (E), the voltage reading will be approximately 3.5 volts less than the voltage at the Alternator output stud due the resistor inside the Alternator. This is the Alternator sense (E) input to the PCM. These two voltage sense inputs are used and compared during the different diagnostics performed on the EVR system by the PCM.

Condition:
Battery voltage at the Powertrain Control Module (PCM) is less than a calibrated threshold for a set period of time.

Actions:
- The ETC light flash.
- The Battery light illuminate.

Possible causes P0562 Code

• Defective Battery
• Resistance in the Battery positive cable or end
• Resistance in the Battery negative cable or end
• Poor ground connection at the engine block or body connections
• Fused B+ circuit high resistance
• PCM powers and grounds
• Powertrain Control Module (PCM)

Diagnose P0562 Code

Step 1. Check for an active condition

Inspect and test the Battery with the midtronics Battery tester or equivalent for a shorted or dead cell before continuing with this test. Inspect the vehicle for alfamarket accessories that may exeed the Alternator system output. Inspect the fusible link in the charge wire or fuses in the PDC depending on application. If an open fusible link or fuse is found, use the wire diagram/schematic as a guide and inspect the wiring and connectors for damage.

Start the engine and allow it to idle. With the scan tool. navigate to data display and monitor the voltage sense to the PCM.

Is the voltage within 0.2 volts of the target charging voltage?

Yes, perform the PCM intermittent condition.
No, go to step 2.

Step 2. Check for high resistance in the Battery positive circuit
Perform a voltage drop test between the Battery positive (+) post:

• and the Alternator stud.
• and the PDC B+ terminal.

Is the voltage reading above 0.2 volts for either measurement?

Yes, repair the Battery positive (+) circuit for high resistance

No, go to step 3.

Step 3. Check for high resistance in the Battery ground cable

Perform a voltage drop test on the Battery negative (-) cable from the Battery cable end;

• to the engine ground eyelet.
• to the body ground eyelet.

Is the voltage reading above 0.2 volts for either measurement?

Yes, repair the Battery ground circuit for high resistance.

No, go to step 4.

Step 4. Check the fused B+ circuit for high resistance

Turn the ignition off, disconnect the PCM harness connector. Star the engine and allow it to idle, using a voltmeter measure the voltage at the fused B+ circuit at the PCM harness connector. Compare the voltage reading to the voltage at the Alternator output stud. Approximately 2.0 Ohms of resistance in this circuit can drop the Battery by approximately 0.5 volts.

Is te voltage within 0.2 volts of the measurement at the Alternator ouput stud?

Yes, go to step 5.

No, repair the fused B+ circuit for high resistance

Step 5. Check related PCM and component connections

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