Code
P0560
HUMMER
P — Powertrain
System Voltage
Views:
UK: 24
EN: 30
RU: 20
AI status
Completed
Completed
100%
Causes
- Weak, discharged, or failing battery
- Corroded, loose, or damaged battery terminals or cable connections
- Faulty alternator (generator) or internal voltage regulator
- Broken, slipping, or missing drive belt for the alternator
- Open or shorted wiring between alternator, battery, and PCM
- Poor ground connections (engine or chassis grounds)
Symptoms
- Battery warning lamp or charging system light on dash
- Dim or flickering headlights and interior lights
- Electrical accessories operating erratically
- Hard starting or no-crank if battery becomes severely discharged
- Engine stalling or poor running if voltage drops while driving
- Blown fuses or loss of specific electrical functions
What to check
- Visual inspection of battery, terminals, cables, alternator, and drive belt for damage or looseness
- Check battery resting voltage with a DVOM (expected ~12.4–12.8 V for a healthy battery)
- Measure charging voltage at battery with engine idling and under higher RPM (expected ~13.5–14.8 V)
- Scan for additional DTCs and view live data for system voltage and alternator parameters
- Inspect and wiggle wiring/connectors at alternator and PCM while monitoring voltage for intermittent changes
- Check main engine/chassis ground straps for corrosion or looseness
Signal parameters
- Battery at rest (engine off): ~12.4–12.8 V (fully charged)
- Cranking: typically 9.6–11.5 V depending on starter and battery condition
- Charging (engine idle): ~13.5–14.8 V
- Charging (higher RPM or load): may reach ~14.0–14.8 V; sustained >15.5–16 V is abnormal
- System low threshold often near or below ~11.5–12.0 V (varies by manufacturer)
- System high threshold commonly above ~15.5–16.0 V (varies by manufacturer)
Diagnostic algorithm
- Read and record freeze-frame data and all stored DTCs with a professional scan tool.
- Visually inspect battery, terminals, cable condition, and alternator belt tension; clean and tighten battery connections if corroded or loose.
- Measure and record battery voltage with engine off. If below ~12.4 V, charge the battery then retest or perform a load/CCA test to confirm battery health.
- Start engine and measure voltage at battery positive: confirm charging voltage ~13.5–14.8 V. If charging voltage is low or absent, proceed to alternator checks.
- Verify alternator output at the alternator terminal and check for regulator signals at the PCM (if applicable). Inspect alternator connector pins for corrosion or damage.
- Check main engine and chassis grounds and repair any poor connections; recheck system voltage after ground repairs.
- Inspect wiring between alternator, battery, and PCM for opens/shorts and repair as needed. Wiggle test connectors/wiring while monitoring voltage for intermittent faults.
- Check fusible links and charging system fuses; replace any blown items and determine cause of failure.
- If alternator output is excessive (over-voltage), test/replace voltage regulator or alternator assembly. If alternator output is insufficient and battery is good, replace or rebuild alternator.
- If wiring and charging system test good but code persists, test PCM voltage sensing circuit and replace or reprogram PCM only after confirming harness and components are good.
- Clear codes, perform a road test under load, and re-scan to confirm the issue is resolved.
Likely causes
- Corroded/loose battery terminals or cable
- Failed alternator or internal regulator
- Weak or failing battery unable to hold charge
- Poor ground or damaged wiring between alternator and battery/PCM
Fault status
Status
P0560 — System Voltage: The powertrain control module has detected the vehicle electrical system voltage outside the expected range. Causes include battery, alternator/regulator, wiring, or grounding faults. Further tests are required to isolate the source.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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