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Home / DTC / B1422 — Series interface (K1) connection to instrument cluster (A1)

B1422 — Series interface (K1) connection to instrument cluster (A1)

Detailed page for trouble code B1422.

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Code

B1422

MERCEDES-BENZ B — Body

Series interface (K1) connection to instrument cluster (A1)

Brand: MERCEDES-BENZ
Type: B — Body
AI status
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Page language: EN

Causes

  • Open, short or high-resistance wiring between K1 and A1
  • Corroded, loose or damaged connector pins at K1 or A1
  • Blown fuse or missing power/ground to one of the modules
  • Faulty K1 module (series interface) or faulty instrument cluster (A1)
  • Software/firmware mismatch or ECU configuration error
  • Interference or short to battery/ground on the communication bus

Symptoms

  • Instrument cluster displays errors or goes blank
  • Loss or intermittent operation of cluster functions (gauges, indicators, messages)
  • One or more warning lights illuminated (communication-related)
  • Stored B1422 and possibly other communication-related DTCs
  • Certain vehicle features tied to the cluster operate incorrectly or not at all

What to check

  • Verify and record battery voltage (engine off and cranking) and check charging system
  • Scan for additional DTCs; note freeze frame and event frequency
  • Visually inspect wiring harnesses and connectors at K1 and A1 for damage, corrosion, water ingress or bent pins
  • Check related fuses and module power/ground circuits
  • Backprobe connectors and measure supply voltages and ground continuity
  • Wiggle harness and connectors while monitoring live data or DTC status for intermittent faults

Signal parameters

  • Battery supply voltage to modules: approx. 11–14.5 V (vehicle dependent)
  • Module ground continuity: low resistance (near 0 Ω)
  • Communication bus idle voltage per manufacturer (e.g., CAN nodes ~2.5 V nominal on each line; LIN/serial bus levels differ) — compare to wiring diagram
  • Bus termination resistance (CAN): approx. 60 Ω total (two 120 Ω in parallel) — confirm with wiring diagram
  • No short to battery or ground on the communication line when inactive

Diagnostic algorithm

  1. Retrieve all stored codes and freeze-frame data with a capable Mercedes diagnostic tool; note any related U or B codes.
  2. Check battery voltage and fuses; inspect power and ground circuits for K1 and A1.
  3. Visually inspect connectors and harnesses at K1 and instrument cluster for corrosion, damage, or water intrusion; repair as needed.
  4. With ignition on, backprobe power, ground and communication lines at the connectors; verify expected voltages and bus idle levels per wiring diagram.
  5. Perform continuity/resistance check between the K1 and A1 pin locations with ignition off; repair any open/shorts.
  6. If intermittent, perform wiggle/strain tests while monitoring live data or DTC reappearance to locate broken wires or poor contacts.
  7. If wiring and power/ground are good, update module software and re-initialize communications per manufacturer procedures.
  8. If fault persists and diagnostics point to a module, swap with a known-good unit or follow manufacturer replacement/repair procedures for K1 or instrument cluster.
  9. After repairs, clear codes and road test to confirm the fault does not return; re-check for stored codes.

Likely causes

  • Damaged connector or wiring harness between K1 and instrument cluster
  • Poor ground or low battery/unstable supply voltage to one of the modules
  • Intermittent connector contact (water ingress, corrosion)
  • Failed series interface (K1) module or failed instrument cluster (A1)
  • Prior service left a connector unseated or pin bent

Fault status

⚠️ Status
Communication error: series interface (K1) connection to instrument cluster (A1) interrupted — open/short/intermittent link detected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

Similar codes

B1420 B1421 B1423 U0100 U0073 U0155
856

Browse 856 MERCEDES-BENZ manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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