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Home / DTC / B1087 — Recirc output circuit high(open)

B1087 — Recirc output circuit high(open)

Detailed page for trouble code B1087.

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Code

B1087

MITSUBISHI B — Body

Recirc output circuit high(open)

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

Causes

  • Open or damaged wiring between HVAC control module and recirculation actuator
  • Corroded or loose connector at the actuator or control module
  • Failed recirculation actuator (motor/servo) or internal open winding
  • Short to battery (intermittent) or short to ground in output circuit
  • Blown fuse or poor chassis ground for HVAC module
  • Faulty HVAC control module or internal driver circuit

Symptoms

  • Recirculation mode will not change or is stuck in one position (fresh/recirc)
  • Recirc indicator on dash does not respond correctly
  • Reduced HVAC performance (unwanted outside air or poor cabin circulation)
  • Unusual HVAC noise or actuator not moving
  • Possible intermittent operation or persistent DTC illuminated

What to check

  • Scan HVAC module for B1087 and any related codes; note freeze frame/live data
  • Visually inspect wiring and connectors for damage, corrosion, or disconnection at actuator and control module
  • Check HVAC-related fuses and battery/ignition power supply to the module
  • Back-probe actuator connector while operating recirc command and observe voltages/signals
  • Measure continuity and resistance between control module pin and actuator connector (check for open)
  • Check ground integrity for HVAC module and actuator ground

Signal parameters

  • When commanded ON: control output typically presents near battery voltage (~12 V) or a PWM drive (0–12 V) depending on model
  • When commanded OFF: control output typically near 0 V (ground) or low-duty PWM
  • Actuator feedback/position sensor (if present): 0–5 V range depending on position
  • Actuator motor winding typical resistance: low ohms to tens of ohms; an open reading (OL/infinite) indicates internal open
  • Expected circuit continuity: near 0 ohms through wiring/connector; open = infinite

Diagnostic algorithm

  1. Retrieve and record DTC(s) and freeze-frame data with a scan tool. Clear codes and re-run to confirm recurrence.
  2. Visually inspect harnesses and connectors at the recirculation actuator and HVAC control module for damage, corrosion, or water ingress.
  3. Verify fuses and power/ground to the HVAC control module. Repair any power/ground issues before proceeding.
  4. With ignition on, back-probe the actuator connector and command recirc on/off via the switch or scan tool. Observe control output voltage and any feedback signal.
  5. Measure continuity between the module output pin and actuator pin. An open indicates wiring/connector fault; repair as needed.
  6. If continuity is good, bench-test the actuator by applying proper test voltage to confirm mechanical/electrical operation and measure current draw (excessive or no current indicates actuator fault).
  7. If actuator tests good and wiring is intact, suspect the HVAC control module output driver. Verify with scope if available or swap with known-good module per manufacturer guidance.
  8. After repairs, clear codes and verify proper operation of recirculation function over multiple cycles and road test if applicable.

Likely causes

  • Wiring harness open at connector or chafed wire to actuator
  • Corroded/poor connector at recirc actuator
  • Recirculation actuator motor failure (open winding or internal electronics failed)
  • HVAC control module output transistor failed (less common)

Fault status

⚠️ Status
Recirc output circuit high (open) — control module detects high voltage or open circuit on recirculation actuator output.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1086 B1088 B1097 B10A0
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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