Code
B2404
MITSUBISHI
B — Body
STL.unit comm.(function code)
Views:
UK: 11
EN: 15
RU: 8
AI status
Completed
Completed
100%
Causes
- Poor battery or low supply voltage to STL unit
- Blown fuse or open/short in power/ground circuit for STL unit
- Damaged, corroded or loose connector(s) at STL unit or gateway module
- Intermittent or failed CAN/LIN bus wiring between STL unit and other modules
- Software/version mismatch or configuration error in module(s)
- Internal fault in the STL unit or gateway/ECU
Symptoms
- Steering lock/unlock or related STL functions unavailable or intermittent
- Key recognition, immobilizer, or start condition affected (possible crank/no-start)
- Warning lamp or message related to security, steering lock, or communication present
- Related modules show communication errors when scanned with a diagnostic tool
- Intermittent faults that may clear then recur
What to check
- Scan all modules with a capable diagnostic tool; record B2404 and any other stored U/B codes
- Visually inspect STL unit connector and harness for damage, corrosion, pin push-out or water ingress
- Check battery condition and voltage (engine off and during cranking)
- Verify relevant fuses and relays for STL/unit power circuits
- Perform wiggle test while monitoring network for code set or changes
- Check for related CAN/LIN bus codes (U-codes) that indicate broader network issues
Signal parameters
- STL unit supply voltage: ~12 V with ignition ON (verify at module connector)
- Ground continuity: near 0 Ω to chassis ground from module ground pin
- CAN bus recessive voltage: approximately 2.5 V on both CANH and CANL (compare to other modules)
- CAN bus dominant level: CANH rises and CANL falls under activity (use oscilloscope to confirm frames)
- Communication traffic: module should appear on bus during key ON when scanned (use diagnostic tool to list live modules)
Diagnostic algorithm
- Connect a manufacturer-capable scan tool and read all stored and pending codes; note freeze-frame data
- Clear codes, then cycle ignition and attempt to reproduce the fault to confirm persistence
- Check battery voltage (should be ≥12.4 V at rest) and charging system health; weak supply can cause communication faults
- Visually inspect and secure STL unit connectors and wiring; repair any damaged insulation or terminals
- Verify fuses/relays for the STL unit circuit and restore any blown fuses; re-test
- Measure voltage at the STL module power pin with ignition ON; verify ground continuity to chassis
- Using a multimeter/oscilloscope, measure CANH and CANL voltages at the STL connector and at a known-good module; compare idle and active waveforms
- If wiring and bus signals are good but fault persists, swap with a known-good STL unit (if possible) or replace the STL module per service manual
- After repairs, clear codes and perform a full communication scan and function test (steering lock behavior, security system operation)
Likely causes
- Open/short in harness to STL unit (power, ground, communication lines)
- Failed STL unit (internal electronics)
- Faulty junction/gateway module or intermediate control module
- Poor ground or weak battery causing communication errors
- Corrosion/poor terminal contact at connectors
Fault status
Status
STL unit communication error — function code exchange failed or module not responding
Repair difficulty: Medium
Diagnostic time: 1.0 - 2.5 hours
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