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Home / DTC / B2646 — Ambient Light Sensor Circuit Range

B2646 — Ambient Light Sensor Circuit Range

Detailed page for trouble code B2646.

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11,660generic
22,491specific
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Code

B2646

HUMMER B — Body

Ambient Light Sensor Circuit Range

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

Causes

  • Faulty ambient light sensor (damaged or contaminated)
  • Open, short, or high-resistance wiring in sensor harness
  • Poor or corroded connector/terminals at sensor or module
  • Bad ground or missing reference (5V) supply to the sensor
  • Body Control Module (BCM) or lighting control module fault
  • Incorrect sensor alignment or obstruction (tinted film, dirt)

Symptoms

  • Automatic headlights or interior auto-dimming operate incorrectly (stay on, stay off, or flicker)
  • Instrument cluster or infotainment brightness wrong for ambient conditions
  • DTC B2646 stored and possibly illuminated message or service indicator
  • Inconsistent or erratic ambient light sensor value in live data

What to check

  • Visual inspection of sensor location (usually near windshield/rearview mirror) for obstruction, dirt, or aftermarket films
  • Inspect connectors and wiring for corrosion, damage, or looseness
  • Scan tool: read freeze frame and live data for ambient light sensor voltage/level
  • Check for related DTCs (communication or other body/lighting codes)
  • Verify power and ground at the sensor connector (reference voltage and ground continuity)
  • Wiggle-test harness while observing live data for intermittent changes

Signal parameters

  • Reference supply: typically 5.0 V reference from BCM (verify exact spec in OEM manual)
  • Signal output: 0–5 V analog (typical) or a sensor-specific voltage proportional to lux; expected to vary with light level (low voltage = dark, higher voltage = bright) — confirm with OEM data
  • Ground: low-resistance chassis ground at sensor
  • Normal live-data behavior: stable change when moving between dark and bright conditions, no rapid jumps or stuck values

Diagnostic algorithm

  1. Use a scan tool to read the ambient light sensor live data and freeze frame. Note sensor voltage/level in current lighting conditions. Clear code and try to reproduce.
  2. Visually inspect sensor lens, windshield at sensor area, and remove any dirt, condensation, or aftermarket tint that could obscure the sensor.
  3. With ignition ON, backprobe the sensor connector: verify reference voltage (usually ~5 V), signal voltage, and ground continuity. Compare signal voltage in dark vs. bright light — it should change smoothly.
  4. Check continuity between sensor ground and chassis ground, and between sensor reference pin and BCM reference output. Look for opens or high resistance.
  5. Inspect the harness for damaged insulation, chafe, or water intrusion. Wiggle wiring and observe live data for intermittent faults.
  6. If reference and ground are present and wiring is good, disconnect the sensor and measure sensor output per OEM procedure (resistance or voltage). If out of spec, replace the sensor.
  7. If new sensor exhibits same out-of-range values, check BCM inputs, related grounds, and scan tool for BCM faults. Reprogram/flash BCM if service information advises.
  8. After repair or replacement, clear codes and verify proper operation under varied ambient conditions. Document test results.

Likely causes

  • Contaminated/obstructed sensor lens causing incorrect readings
  • Wiring short to battery or ground at the sensor connector
  • Loose or corroded connector at sensor or BCM
  • Failed ambient light sensor element

Fault status

⚠️ Status
Ambient Light Sensor Circuit Range — the control module has detected the ambient light sensor signal is outside the expected range or is changing abnormally for the detected conditions. This sets a body code when the sensor output fails threshold checks or diagnostic plausibility tests.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B2645 B2647 B2610 U0140 U0073
Repair manuals

Manual library for HUMMER

138

Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

HUMMER

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Code

B2646

LAND ROVER B — Body

Antenna circuit - open circuit 1

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

Causes

  • Faulty ambient light sensor (damaged or contaminated)
  • Open, short, or high-resistance wiring in sensor harness
  • Poor or corroded connector/terminals at sensor or module
  • Bad ground or missing reference (5V) supply to the sensor
  • Body Control Module (BCM) or lighting control module fault
  • Incorrect sensor alignment or obstruction (tinted film, dirt)

Symptoms

  • Automatic headlights or interior auto-dimming operate incorrectly (stay on, stay off, or flicker)
  • Instrument cluster or infotainment brightness wrong for ambient conditions
  • DTC B2646 stored and possibly illuminated message or service indicator
  • Inconsistent or erratic ambient light sensor value in live data

What to check

  • Visual inspection of sensor location (usually near windshield/rearview mirror) for obstruction, dirt, or aftermarket films
  • Inspect connectors and wiring for corrosion, damage, or looseness
  • Scan tool: read freeze frame and live data for ambient light sensor voltage/level
  • Check for related DTCs (communication or other body/lighting codes)
  • Verify power and ground at the sensor connector (reference voltage and ground continuity)
  • Wiggle-test harness while observing live data for intermittent changes

Signal parameters

  • Reference supply: typically 5.0 V reference from BCM (verify exact spec in OEM manual)
  • Signal output: 0–5 V analog (typical) or a sensor-specific voltage proportional to lux; expected to vary with light level (low voltage = dark, higher voltage = bright) — confirm with OEM data
  • Ground: low-resistance chassis ground at sensor
  • Normal live-data behavior: stable change when moving between dark and bright conditions, no rapid jumps or stuck values

Diagnostic algorithm

  1. Use a scan tool to read the ambient light sensor live data and freeze frame. Note sensor voltage/level in current lighting conditions. Clear code and try to reproduce.
  2. Visually inspect sensor lens, windshield at sensor area, and remove any dirt, condensation, or aftermarket tint that could obscure the sensor.
  3. With ignition ON, backprobe the sensor connector: verify reference voltage (usually ~5 V), signal voltage, and ground continuity. Compare signal voltage in dark vs. bright light — it should change smoothly.
  4. Check continuity between sensor ground and chassis ground, and between sensor reference pin and BCM reference output. Look for opens or high resistance.
  5. Inspect the harness for damaged insulation, chafe, or water intrusion. Wiggle wiring and observe live data for intermittent faults.
  6. If reference and ground are present and wiring is good, disconnect the sensor and measure sensor output per OEM procedure (resistance or voltage). If out of spec, replace the sensor.
  7. If new sensor exhibits same out-of-range values, check BCM inputs, related grounds, and scan tool for BCM faults. Reprogram/flash BCM if service information advises.
  8. After repair or replacement, clear codes and verify proper operation under varied ambient conditions. Document test results.

Likely causes

  • Contaminated/obstructed sensor lens causing incorrect readings
  • Wiring short to battery or ground at the sensor connector
  • Loose or corroded connector at sensor or BCM
  • Failed ambient light sensor element

Fault status

⚠️ Status
Ambient Light Sensor Circuit Range — the control module has detected the ambient light sensor signal is outside the expected range or is changing abnormally for the detected conditions. This sets a body code when the sensor output fails threshold checks or diagnostic plausibility tests.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B2645 B2647 B2610 U0140 U0073
320

Browse 320 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

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