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Home / DTC / B212D — IG SW ON POS.circuit open

B212D — IG SW ON POS.circuit open

Detailed page for trouble code B212D.

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Code

B212D

MITSUBISHI B — Body

IG SW ON POS.circuit open

Brand: MITSUBISHI
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Blown fuse or open circuit in the ignition power fuse/line
  • Faulty ignition switch (ON position contact failed)
  • Disconnected, corroded or damaged connector at the ignition switch or ECU/BCM
  • Chafed or broken wiring between ignition switch and control module
  • Faulty relay controlling IG-ON circuit
  • Aftermarket accessory or alarm/immobilizer interfering with the IG-ON feed

Symptoms

  • No power to ignition-switched circuits when key is ON (accessories, ECU power)
  • Engine will not crank or start (if IG-ON supply required for ECU/starter circuit)
  • Instrument cluster or indicator lights off or intermittent when key ON
  • Related warning lamps or immobilizer warnings
  • Intermittent loss of electrical functions that should be powered with key ON

What to check

  • Read freeze frame and related DTCs with a scan tool
  • Verify battery voltage (should be ~12.4–12.8 V with engine off, ~13.5–14.5 V running)
  • Check relevant fuses and relays for the IG-ON/ignition feed
  • Visually inspect ignition switch connector, wiring harness, and ECU/BCM connector for damage or corrosion
  • Backprobe IG-ON terminal at ignition switch and at control module with key in OFF/ACC/ON positions
  • Perform continuity test between ignition switch IG-ON terminal and the module pin

Signal parameters

  • IG-ON terminal voltage with key in ON: approx battery voltage (11–14 V)
  • IG-ON terminal with key OFF: near 0 V (open)
  • Continuity between ignition switch IG-ON terminal and module terminal when key ON: low resistance (
  • Voltage drop under load on IG-ON feed: less than ~1 V from battery to IG-ON terminal with loads connected

Diagnostic algorithm

  1. Confirm code and record freeze-frame/related codes with a scanner. Do not rely on a single code — check history.
  2. Verify battery condition and main power supply to modules. A low battery can cause misleading results.
  3. Inspect fuses/relays for the ignition/IG-ON circuit. Replace any blown fuses and retest.
  4. With key OFF, locate and visually inspect the ignition switch connector and harness for corrosion, loose terminals, or damage.
  5. Backprobe the ignition switch IG-ON output and measure voltage with key in OFF, ACC, and ON positions. Expect ~battery voltage in ON.
  6. Backprobe the corresponding module/BCM/ECU input pin for IG-ON and verify it sees the same voltage when key ON.
  7. If voltage present at switch but not at module, perform continuity/resistance check between switch and module pins; repair any open or high-resistance wiring/connectors.
  8. If no voltage at switch IG-ON terminal, test/replace ignition switch or internal switch contacts and retest.
  9. If wiring and switch test good but module still reports open, inspect for aftermarket devices or relays that may interrupt the feed; disconnect accessories and retest.
  10. If all wiring and switches are good, consider module input fault — consult wiring diagrams and manufacturer service info before replacing module.
  11. After repairs, clear the code, perform functional tests, and verify the code does not return under normal operation.

Likely causes

  • Blown fuse or open wiring in IG-ON circuit
  • Corroded/loose connector at ignition switch or body control module
  • Failed ignition switch contact for ON position
  • Intermittent open caused by wiring chafe or connector corrosion

Fault status

⚠️ Status
Ignition switch ON circuit open — control module did not detect expected IG-ON voltage.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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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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