Code
B1091
MITSUBISHI
B — Body
A/M DMPR.motor blocked (right)
Views:
UK: 19
EN: 31
RU: 22
AI status
Completed
Completed
100%
Causes
- Foreign object or debris blocking damper/flap
- Stripped or damaged actuator gears
- Seized or failed damper motor
- Broken linkage between motor and damper
- Faulty position sensor inside actuator
- Open/short in motor power or signal wiring, or poor connector connection
Symptoms
- HVAC mode/air distribution stuck or cannot change to desired vents
- Unusual noise (grinding, clicking) from right dash area when changing modes
- No airflow change from right-side vents or inconsistent flow
- HVAC system may default to a single mode or display error related to A/M damper
What to check
- Read and record freeze frame and live data with an OEM-level scan tool and confirm B1091 is active
- Operate the HVAC mode change while listening at right dash for motor movement
- Visually inspect right dash/center console vent area for foreign objects or broken flaps
- Perform actuator run/diagnostic routine with scan tool (if available) to command full travel
- Inspect connector at right damper actuator for corrosion, bent pins, and secure fit
- Check supply voltage and ground at actuator connector while commanding movement (approx. vehicle battery voltage expected on supply)
Signal parameters
- Power supply: approx. vehicle battery voltage (~11–14 V) present at motor supply terminal when commanded
- Ground: solid ground continuity to chassis expected
- Position feedback: variable voltage (often ~0.5–4.5 V) or potentiometer output that changes with actuator travel
- Actuator motor coil resistance: typically low ohms (consult service manual for exact value)
- Control signal: PWM or switched 12 V command from HVAC control module during movement (frequency varies by manufacturer)
Diagnostic algorithm
- Verify complaint: with ignition ON, use scan tool to read codes and run HVAC actuator diagnostic for right A/M damper. Note whether code is current or intermittent.
- Reproduce: attempt to change HVAC mode while listening for actuator movement at right dash. If no movement and clicking/grinding present, likely mechanical failure.
- Visual inspection: remove right dash/grille trim to access actuator. Look for foreign objects, broken flaps, or disconnected linkages.
- Connector and wiring: inspect and wiggle harness while commanding actuator. Check for power and ground at the actuator connector when it should move. Backprobe carefully or use break-out leads.
- Measure feedback: monitor position sensor voltage while commanding movement. Lack of change indicates internal sensor or mechanical problem.
- Bench test actuator: remove actuator and apply controlled 12 V to motor terminals (or use service procedure) to verify motor spins and feedback changes. Observe for stripped gears or seized shaft.
- Repair or replace: if actuator fails bench test or shows mechanical damage, replace right damper actuator assembly and any damaged linkages. Clear codes and retest.
- Wiring/control module: if actuator bench-tests good but no power/commands at connector, trace wiring to fuse block and HVAC control module, repair open/shorts, or consider control module fault only after wiring checks.
- Final verify: reassemble, run actuator/auto mode routines until codes do not return, and confirm correct airflow distribution and absence of noise.
Likely causes
- Damper actuator motor failure (right)
- Mechanical obstruction in duct or broken flap linkage
- Damaged actuator internal gears or potentiometer
- Wiring harness connector corroded or pin pushed out
Fault status
Status
Right automatic-mode damper motor is blocked or not reaching commanded position. HVAC air distribution may not change properly; actuator or its wiring likely faulty.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
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