P0562 — System Voltage Low
P0562 sets when system voltage drops below the calibrated minimum for a calibrated time, usually while the engine is running. Voltage-drop testing under load finds high-resistance connections that a simple voltage check misses and prevents unnecessary alternator replacement.
Fault Overview
Failing alternator, loose or corroded battery cables, high resistance at grounds, failing battery, excessive electrical load, and poor alternator sense circuit are the primary causes. Measure voltage at the battery and at the PCM under load — a large difference indicates cable or ground resistance.
Engine & Platform Coverage
Symptoms
- •P0562
- •system voltage low
- •low battery voltage
- •alternator code
- •P0562 charging system
Possible Causes
- 1.Failing alternator
- 2.Loose or corroded battery cables
- 3.High resistance at grounds
- 4.Failing battery
- 5.Excessive electrical load
- 6.Poor alternator sense circuit
Wiring & Circuit Notes
Battery cables, main ground straps, alternator power and sense circuits. Check for voltage drop on positive and ground sides under load.
DVOM Specs & Sensor Tests
Battery voltage KOEO and running. Alternator output at idle and 2000 rpm with loads on. Voltage drop tests on cables and grounds (max 0.2 V).
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
5 steps locked behind Technician Mode- 1Step 1 — Measure Battery Voltage KOEO: Measure battery voltage key-on engine-off. Should be 12.4–12.8 V for a healthy battery.
- 2Step 2 — Measure Running Voltage at Idle and with Loads: Measure running voltage at idle and with loads on (A/C, headlights, rear defroster). Should be 13.5–14.8 V.
- 3Step 3 — Perform Voltage-Drop Tests on Positive and Ground Cables: Perform voltage-drop tests on positive and ground cables under load. More than 0.2 V drop indicates high resistance.
- 4Step 4 — Load-Test the Battery: Load-test the battery. A weak battery can cause P0562 even if the alternator is good.
- 5Step 5 — Test Alternator Output: Test alternator output at idle and 2000 rpm with loads on.
- 6Step 6 — Repair Cables, Grounds, Battery, or Alternator as Indicated: Repair cables, grounds, battery, or alternator based on the test results.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
Typical Repair Costs
Clean/tighten cables and grounds $20–100; replace battery $100–300; replace alternator $200–600.
Start Diagnosing This Fault Now
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Summary
Use the AI Diesel Tech diagnostic engine to run this code through a structured, evidence-gated sequence and get a confirmed root cause before any parts are replaced.