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Home / DTC / B1093 — Sun sensor circuit low

B1093 — Sun sensor circuit low

Detailed page for trouble code B1093.

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B1093

MITSUBISHI B — Body

Sun sensor circuit low

Brand: MITSUBISHI
Type: B — Body
AI status
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Page language: EN

Causes

  • Faulty sun (solar) sensor
  • Open or shorted wiring in sun sensor harness (short to ground)
  • Corroded, loose or damaged connector at sensor or control module
  • Loss of reference/power supply from the control module or blown fuse (rare)
  • Intermittent wiring fault due to chafing or water ingress
  • Control module input circuit fault (less common)

Symptoms

  • Automatic climate control uses incorrect sun load compensation (climate may over- or under-compensate)
  • Automatic headlamp/lighting may behave incorrectly in varying light conditions
  • Stored B1093 fault and possibly other related B1xxx body codes
  • Luminosity/ambient light reading in scan tool shows near-zero or stuck-low value
  • Dashboard/AC system may show a warning or reduced functionality (model dependent)

What to check

  • Read and record freeze frame and live data with a scan tool — observe sun sensor value while changing light (shade/bright sunlight)
  • Visually inspect sun sensor location (usually on top of dashboard) and its connector for damage, corrosion or moisture
  • Inspect wiring harness from sensor to the control module for chafing, pinched sections, or repairs; look for signs of rodent damage
  • Backprobe the sensor connector and measure signal voltage relative to vehicle ground while exposing sensor to bright light and then shading it
  • Check for proper reference/power supply (if applicable) at the sensor connector (typically a 5V reference or vehicle battery switched feed)
  • Check continuity between sensor connector and control module connector; check for short to ground (infinite or near 0Ω where not expected)

Signal parameters

  • Typical reference/power: 5 V reference (or switched 12 V on some designs) supplied by control module — verify in service manual
  • Sun sensor output (depending on light): approx. 0.1–4.5 V — low circuit typically
  • Fault condition: stuck or constant ~0 V (short to ground) or no signal change with changing light indicates low circuit
  • Open circuit: no continuity between sensor signal pin and control module (infinite resistance)
  • Resistance: internal sensor resistance varies widely; do not rely on single fixed ohm reading without manufacturer spec

Diagnostic algorithm

  1. Retrieve codes and live data with a scan tool. Confirm B1093 is current and note any related codes (e.g., other body sensor codes).
  2. Perform a visual inspection of sensor, connector and harness for damage, corrosion or water ingress. Repair any obvious damage before further testing.
  3. Backprobe the sensor connector: with ignition ON, measure reference voltage and signal voltage. While illuminating the sensor (bright sunlight or flashlight) verify the signal rises. If signal is low and does not change, continue.
  4. Check for short to ground: disconnect sensor and measure resistance between the signal pin and chassis ground. Low resistance indicates a short to ground in harness.
  5. Check continuity between sensor signal pin and the control module input pin. Repair any open circuit.
  6. If wiring and connector are good but sensor output stays low or does not respond to changing light, replace the sun sensor.
  7. If replacing the sensor does not clear the fault, verify the control module’s reference supply and input circuit. Repair or reprogram/replace the control module only after confirming wiring and sensor are good.
  8. After repairs, clear codes and retest under varying light conditions to confirm proper operation and that the code does not return.

Likely causes

  • Sun sensor failed (internal short or degraded photodiode)
  • Pin corrosion or bent pins at sensor connector causing poor contact
  • Wire chafed and shorted to chassis ground near dash or A-pillar
  • Connector contaminated with moisture causing low voltage
  • Control module not supplying reference voltage or input circuit damaged

Fault status

⚠️ Status
Sun sensor circuit low — control module detects sun sensor signal below expected threshold (possible short to ground, open/failed sensor, or wiring fault).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

B1090 B1091 B1092 B1094 B1100
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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