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Home / DTC / B2802 — Power voltage too low

B2802 — Power voltage too low

Detailed page for trouble code B2802.

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Code

B2802

MITSUBISHI B — Body

Power voltage too low

Brand: MITSUBISHI
Type: B — Body
AI status
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Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connection or corrosion
  • Faulty or slipping alternator/voltage regulator
  • Blown or poor fuse/fusible link in the module power feed
  • Loose, corroded, or damaged power/ground wiring or connectors
  • High parasitic current drain when ignition is off

Symptoms

  • Stored B2802 DTC present (may be accompanied by other voltage/communication codes)
  • Possible warning lamps on dash (battery/charging or associated system lights)
  • Intermittent loss of function for body electrical systems (windows, locks, HVAC, infotainment)
  • Vehicle may not start or may crank slowly if battery is severely low
  • Modules may reset or show communication errors when voltage dips
  • Electrical accessories operate weakly or erratically

What to check

  • Read and record freeze-frame and any related codes and live data (module supply voltage)
  • Visually inspect battery, terminals, and cable condition for corrosion, tightness, and damage
  • Measure battery open-circuit/resting voltage (key off) with a digital multimeter
  • Measure battery voltage while cranking and measure charging voltage at idle and ~2000 rpm (engine running)
  • Check voltage at the affected module’s power and ground pins (compare to battery positive and chassis ground)
  • Verify integrity of fuses/fusible links and any relay in the module power feed

Signal parameters

  • Typical resting battery voltage: ~12.4–12.8 V (fully charged)
  • Typical charging voltage (engine running): ~13.5–14.8 V
  • Low-voltage condition often flagged when supply falls below ~9–11 V (manufacturer threshold may vary)
  • Severe cranking voltage drop: below ~8–9 V can cause module resets or multiple DTCs
  • Parasitic draw normal range: typically

Diagnostic algorithm

  1. Read all stored codes and freeze-frame data. Note any related communication or system voltage codes (P0562, U-codes).
  2. Visually inspect battery, cable ends, ground straps and harness to the affected module. Repair obvious defects.
  3. Measure and record battery voltage at rest. If below ~12.4 V, charge or test battery. If battery fails load test, replace battery.
  4. With engine running, measure charging voltage at battery and at module power terminal. Confirm charging system provides ~13.5–14.8 V. Repair alternator/drive belt as required.
  5. Check voltage at the module connector with key ON and engine running; compare to battery voltage. If there is significant drop, trace and repair wiring/connector/fuse/relay supplying the module.
  6. If voltage appears normal but the code returns, perform a parasitic current draw test to identify aftermarket drains or short circuits.
  7. Clear codes, then reproduce conditions (start/drive, accessory load, cranking) while monitoring module voltage with a data logger or scope to catch intermittent dips.
  8. If wiring and charging system are good and low-voltage is still reported, suspect internal module fault; consult wiring diagrams, check for TSB/software updates, and consider module repair or replacement per manufacturer procedures.
  9. After repairs, clear codes and verify the issue is resolved with a test drive and confirm no reoccurrence of B2802.

Likely causes

  • Battery state of charge low or battery failing (high internal resistance)
  • Battery terminals dirty, loose or poorly crimped cable ends
  • Alternator not charging (worn brushes, bad diode, regulator failure)
  • Damaged power feed or ground at the module connector
  • Blown main or accessory fuse supplying the affected control module
  • Aftermarket electrical accessory causing excessive draw or voltage drop

Fault status

⚠️ Status
Stored when the control module detects its supply voltage has dropped below the allowable operating threshold (power voltage too low).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.5 hours

Similar codes

P0562 P0563 U0100 U0121 B2799
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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