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Home / DTC / P1602 — A / Dconverter | Batteryvoltage | Voltagecircuit | Voltage regulator

P1602 — A / Dconverter | Batteryvoltage | Voltagecircuit | Voltage regulator

Detailed page for trouble code P1602.

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P1602

ALFA ROMEO P — Powertrain

A / Dconverter | Batteryvoltage | Voltagecircuit | Voltage regulator

Brand: ALFA ROMEO
Type: P — Powertrain
AI status
Completed
ready
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Page language: EN

Causes

  • Low or high battery/charging system voltage
  • Faulty alternator or voltage regulator
  • Loose, corroded or damaged battery terminals and ground connections
  • Open or shorted wiring between battery/alternator and ECU (voltage sense circuit)
  • Blown fuse or fusible link in charging/battery supply circuit
  • Faulty ECU A/D converter or internal voltage-sensing circuitry

Symptoms

  • Battery warning light or charging system warning on dash
  • Vehicle may not start or cranks slowly
  • Dimming or flickering lights and accessories
  • Erratic instrument cluster behavior or incorrect gauge readings
  • Engine stalling or poor running if ECU limits operation
  • Stored multiple voltage-related fault codes

What to check

  • Read and record freeze-frame data and live battery voltage using a scan tool
  • Check battery resting voltage with engine off (multimeter)
  • Measure charging voltage at battery with engine running (idle and ~2000 rpm)
  • Inspect and clean battery terminals, cable ends and chassis/engine grounds
  • Check fuses and fusible links for battery/ECU supply circuits
  • Inspect wiring and connectors for damage, corrosion, loose pins, or water ingress

Signal parameters

  • Battery voltage (engine off): typical 12.4–12.8 V
  • Charging voltage (engine running, normal): typical 13.5–14.8 V
  • Excessive charging: >15.5 V indicates possible regulator failure
  • Voltage drop across battery terminals under cranking: should be small (
  • AC ripple at alternator output: normally
  • ECU A/D reference (manufacturer-specific): often ~5 V reference — consult wiring diagram before measuring

Diagnostic algorithm

  1. Connect an OEM-capable scan tool, confirm P1602 and note freeze-frame/live voltage values; clear the code and see if it returns.
  2. Visually inspect battery, terminals, engine and chassis grounds, and all related fuses; clean and tighten battery terminals and main ground straps.
  3. Measure battery resting voltage with a digital multimeter; if
  4. Start engine and measure charging voltage at the battery at idle and ~2000 rpm; compare to expected charging range (approx. 13.5–14.8 V).
  5. Perform AC ripple test at alternator/battery to check for diode/rectifier failure; significant ripple requires alternator service or replacement.
  6. With ignition off, inspect and backprobe the ECU battery-sense / B+ / VIN pin and measure presence and stability of battery voltage; check ground reference at ECU.
  7. Check continuity and voltage drop of supply and ground circuits between battery and ECU; repair corroded/poor connections or damaged wiring.
  8. Inspect and test any charging-system control fuses, relays and regulator wiring. Replace faulty components as identified and retest.
  9. If wiring, battery and alternator are verified good and voltage signals are within spec but code persists, suspect internal ECU A/D converter failure; consult manufacturer service procedures for ECU bench testing or replacement.
  10. After repairs, clear codes, perform a road test and monitor voltage and related parameters; confirm P1602 does not return.

Likely causes

  • Weak or discharged battery (low resting voltage)
  • Bad alternator/regulator producing overvoltage or no charge
  • Poor battery negative ground or ECU ground connection
  • Corroded battery terminals or poor cable connection to starter/engine
  • Damaged or loose connector/pin at ECU B+ / VIN / battery-sense pin
  • Intermittent wiring harness fault (pinch, rodent damage)

Fault status

⚠️ Status
ECU reports abnormal battery/charging voltage input to its A/D converter or a failure in the voltage regulation/sensing circuit. Investigate charging system, battery connections, wiring and ECU supply circuits.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 2.5 hours

Similar codes

P0560 P0562 P0563 P0627 P0628
89

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