Code
B29EC
MITSUBISHI
B — Body
Key switch signal:close cycle
Views:
UK: 13
EN: 17
RU: 14
AI status
Completed
Completed
100%
Causes
- Faulty ignition/key switch (worn contacts or internal failure)
- Open, shorted or high-resistance wiring between ignition switch and body/BCM
- Corroded or loose connector at ignition switch or BCM
- Poor battery voltage or weak battery affecting signal levels
- Faulty Body Control Module (BCM) or related control module
- Intermittent CAN/communication error between modules
Symptoms
- Intermittent no-crank or no-start conditions
- Accessory/ignition circuits not switching consistently
- Ignition key or push-start behaves intermittently
- Warning or immobilizer lamp illuminated or flashing
- Stored B29EC (and possibly related communication codes)
What to check
- Read stored/active codes and freeze frame with a scan tool; note time and battery voltage.
- Check battery voltage and charging system; ensure >= 12.4 V (at rest) before testing.
- Inspect ignition switch and steering column area for physical damage or corrosion.
- Check fuses and fusible links for ignition/BCM circuits.
- Visually inspect connectors and wiring between ignition switch and BCM for chafing, corrosion, or pin damage.
- Back-probe ignition switch terminals and monitor voltage while cycling key through OFF/ACC/ON/START.
Signal parameters
- Expected voltages at ignition switch terminals: OFF ≈ 0–1.5 V, ACC/ON/START ≈ battery voltage (~11–14.5 V).
- Logic threshold: closed = >10.0 V (approx), open =
- Start/close pulse duration: should be >100 ms while cranking; multiple short spurious pulses indicate contact bounce or wiring fault.
- No significant voltage drop (
Diagnostic algorithm
- Connect a professional scan tool and confirm B29EC (note freeze frame data and battery voltage).
- Attempt to reproduce the fault while monitoring the ignition switch input with a voltmeter or oscilloscope (back-probe harness).
- Verify battery and charging system health; charge or replace battery if low and retest.
- Inspect and clean connectors at the ignition switch and BCM; reseat connectors and check for bent pins.
- Perform continuity and resistance checks from ignition switch terminals to the BCM input pin(s). Repair any open or high-resistance circuits.
- If intermittent, perform wiggle tests on wiring near the steering column and BCM while observing the signal.
- If wiring and switch test good, remove and bench-test or replace the ignition switch assembly per service manual procedures.
- If ignition switch and wiring are verified good, check BCM power/ground circuits and related modules. Consider reflashing or replacing BCM only after confirming upstream inputs are correct.
- Clear codes and retest to confirm repair. Document any intermittent conditions and re-scan after extended road test.
Likely causes
- Ignition switch contacts worn or intermittent (most common)
- Damaged harness or pin pushed out at connector
- Low battery voltage during test or jump-start event
- Connector corrosion or water ingress at steering column
- BCM input circuit fault or intermittent internal failure
Fault status
Status
Key switch signal — close cycle abnormal or missing. Ignition switch input did not meet expected closed/open voltage or timing.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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