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Home / DTC / B1261 — Solar radiation sensor short to ground

B1261 — Solar radiation sensor short to ground

Detailed page for trouble code B1261.

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Code

B1261

ALFA ROMEO B — Body

Solar radiation sensor short to ground

Brand: ALFA ROMEO
Type: B — Body
AI status
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Page language: EN

Causes

  • Damaged or chafed wiring causing a direct short to chassis ground
  • Corroded, pushed-out or damaged sensor connector / pins
  • Failed solar radiation (sunload) sensor with internal short to ground
  • Improper repair or aftermarket accessory causing wiring contact with body/chassis
  • Climate control module or wiring harness connector fault (less common)

Symptoms

  • HVAC automatic mode not responding to sunlight or behaves incorrectly (overheating or overcooling)
  • Dash message or fault indicator for sunload/solar sensor (in some vehicles)
  • Climate control may remain in a fixed vent/temperature behavior despite changes in light
  • Possible stored B1261 fault code in climate control module

What to check

  • Read stored codes and freeze frame with a diagnostic scan tool; note conditions when fault set
  • Perform a visual inspection of the solar sensor, its mounting, and wiring harness for damage, corrosion, or signs of water entry
  • Inspect connector pins for corrosion, pushed-out pins, bent pins, or melted plastic
  • With ignition ON (engine off), backprobe the sensor connector and measure reference and signal voltages with a digital multimeter
  • Check continuity between the sensor signal pin and chassis ground to confirm a short to ground
  • Wiggle the harness and connector while watching live data or voltage to reproduce intermittent faults

Signal parameters

  • Typical reference supply: 5 V (from climate control/BCM) — verify vehicle-specific spec
  • Expected sensor output: variable 0.5–4.5 V (low in shade/dark, higher in bright sun) — depends on vehicle calibration
  • Short-to-ground symptom: signal ≈ 0.0–0.2 V with ignition ON
  • Short-to-battery symptom: signal near vehicle battery voltage (rare for this sensor)
  • Open-circuit symptom: no reference or signal (infinite resistance)

Diagnostic algorithm

  1. Verify and record DTC B1261 with a scan tool; clear codes and see if B1261 returns
  2. Visually inspect solar sensor location (usually on dash top near windshield) and harness for damage or water intrusion
  3. Disconnect the sensor and inspect connector terminals for corrosion, bent pins or contamination; repair or clean as needed
  4. With the sensor disconnected, measure resistance/continuity between the sensor signal pin (in harness) and chassis ground. A near-zero ohm reading indicates a short to ground in the harness — repair wiring
  5. With ignition ON (engine off) backprobe the climate control harness connector to verify the reference supply (typically 5 V) at the sensor feed wire. If no reference, fault may be in control module or wiring
  6. Reconnect sensor. Backprobe the sensor signal while exposing the sensor to sunlight/shade and observe voltage changes; if signal stays at ~0 V while reference present, suspect failed sensor or short at sensor end
  7. If wiring is intact and reference present but signal stuck low, substitute a known-good sensor or bench-test replacement to confirm sensor failure
  8. If short is only present with the harness connected, isolate sections of wiring and repair damaged insulation or connectors; use proper soldering or OEM-style crimps and seal with heat-shrink or dielectric grease
  9. After repair or sensor replacement, clear codes and perform functional test in varying light conditions and road test to confirm fault does not return

Likely causes

  • Sensor wiring insulation rubbed through and contacting bodywork
  • Water ingress in sensor connector causing corrosion and short
  • Sensor internal electronics failed and shorted to ground
  • Connector retention tab broken allowing pins to back out and short

Fault status

⚠️ Status
Solar radiation sensor circuit short to ground detected by climate control; sunload input reading near 0 V.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5 - 2.0 hours

Similar codes

B1260 B1262 B1270 B1296
89

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