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Home / DTC / B1090 — A/M DMPR.motor blocked (left)

B1090 — A/M DMPR.motor blocked (left)

Detailed page for trouble code B1090.

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Code

B1090

MITSUBISHI B — Body

A/M DMPR.motor blocked (left)

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

Causes

  • Left air‑mix (blend) damper actuator motor seized or mechanically blocked
  • Damper linkage or blend door physically jammed (broken gear, foreign object, misalignment)
  • Damaged or stripped actuator internal gears
  • Broken actuator position sensor or feedback potentiometer
  • Connector corrosion, loose pins or damaged wiring harness to the actuator
  • Short or open in motor power/ground circuit or control signal (PWM)

Symptoms

  • Left-side temperature or blend control does not change (driver side no air‑mix adjustment)
  • HVAC temperature stays too hot or too cold on left side
  • Audible clicking, grinding, or humming from dash when changing temp or vent mode
  • Intermittent or permanent left-side climate control failure
  • Related HVAC DTC(s) present, possible fault lamp or system fault message

What to check

  • Visually inspect left HVAC actuator and surrounding ducting for foreign objects, broken linkages or detached rods
  • Listen at the left dash area while commanding temperature change for abnormal noises (grinding, clicking, stall)
  • With ignition ON, use a scan tool to actuate left air‑mix motor and observe actuator movement and any stored codes
  • Inspect connector for corrosion, bent pins, or loose terminals; wiggle harness while commanding actuator to reproduce fault
  • Check related fuse(s) and chassis ground for integrity
  • Measure voltage at actuator connector while commanding movement (supply should be near battery voltage when driven)

Signal parameters

  • Supply voltage to actuator when commanded: approximately 10–14 V (vehicle battery voltage)
  • Motor coil resistance (typical DC actuator): low ohms range (a few ohms to tens of ohms) — open or very high resistance indicates open circuit
  • Feedback potentiometer voltage: varies with position (commonly ~0.5–4.5 V depending on position)
  • Control signal: PWM or switched 12 V commands from HVAC module — frequency and duty vary by manufacturer
  • Current draw: normal actuators often draw 2–3 A) suggests binding or short (values vary by actuator design)

Diagnostic algorithm

  1. Read and record all HVAC/Body module codes; clear codes and attempt to reproduce B1090 while observing live data.
  2. Perform a visual inspection of left dash area, actuator, linkage and ducting for obstructions, broken parts or loose connectors.
  3. With ignition ON, use a scan tool to command left air‑mix actuator through full travel and observe movement, feedback voltage/position parameter and listen for abnormal noises.
  4. If actuator does not move or stalls, probe the actuator connector: verify supply voltage and ground while commanding movement. If no supply, trace wiring, fuses and HVAC module outputs.
  5. Measure motor coil resistance and check for short to ground/short between terminals. Compare to expected/known good if available. An open or shorted coil requires actuator replacement.
  6. If supply and control signals are present but actuator does not move, remove actuator and inspect gears, shaft and blend door for binding, stripped gears or foreign objects. Manually operate the damper to confirm free movement.
  7. Bench-test removed actuator by applying appropriate voltage/ground (use caution and follow safety) to confirm motor operation and check feedback potentiometer range and smoothness. Measure current draw; excessive current indicates internal mechanical or electrical fault.
  8. Repair or replace faulty components: free or clear obstruction if caused by debris, repair broken linkage if possible, replace actuator if motor or gears are damaged or if feedback sensor fails.
  9. After repair or replacement, reinstall, reconnect, clear codes, perform HVAC actuator relearn/initialization procedure if required by the manufacturer, and verify proper operation across full temperature range.

Likely causes

  • Damper actuator gear stripped or motor seized
  • Debris or foreign object preventing damper movement
  • Wiring connector corrosion or broken wire at left actuator
  • High current draw due to internal motor damage causing module to detect blockage

Fault status

⚠️ Status
B1090 — A/M DMPR.motor blocked (left). The HVAC control module has detected that the left air‑mix (blend) damper motor is blocked or not moving as expected. Inspect actuator, damper linkage, wiring and connectors; repair or replace the actuator if faulty.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2 hours

Similar codes

B1091 B10A0 B10B0 B1050
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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