What Does B1259 Mean?
This code indicates the Body Control Module (BCM) has detected an open circuit in the solar radiation sensor. The solar radiation sensor monitors sunlight intensity to help the automatic climate control system optimize cabin temperature and airflow distribution. An open circuit means there is a break in the electrical path between the sensor and the BCM, preventing proper signal transmission.
Common Causes
40%
Broken or disconnected wiring harness between solar radiation sensor and BCM
35%
Failed solar radiation sensor (internal open circuit)
15%
Corroded or loose connector at sensor or BCM
10%
BCM internal circuit failure or poor ground connection
Diagnostic Steps
1
Step 1: Visually inspect the solar radiation sensor (typically located on dashboard top near windshield) for physical damage, disconnected connector, or signs of moisture intrusion
2
Step 2: Using a multimeter, check for battery voltage (typically 5V reference) at the sensor connector with ignition on. Verify continuity of all wires between sensor connector and BCM connector per wiring diagram
3
Step 3: Disconnect the solar radiation sensor and measure resistance across sensor terminals. Compare readings to manufacturer specifications (typically 1-10k ohms depending on light intensity). An infinite resistance reading confirms sensor internal open circuit
4
Step 4: If wiring and sensor test good, check connector pins for corrosion, bent terminals, or moisture. Clean or repair connectors as needed and apply dielectric grease
5
Step 5: Clear the code, reconnect all components, and monitor live data for solar radiation sensor voltage/signal while varying light exposure to the sensor to confirm proper operation
Estimated Repair Cost
$100 - $400
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an open circuit in the solar radiation sensor. The solar radiation sensor monitors sunlight intensity to help the automatic climate control system optimize cabin temperature and airflow distribution. An open circuit means there is a brea...
The most common cause of B1259 (Solar Radiation Sensor Circuit Open) is: Broken or disconnected wiring harness between solar radiation sensor and BCM
Typical repair costs for B1259 range from $100 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving. This fault only affects automatic climate control operation, which may result in less optimal cabin temperature regulation. The HVAC system will continue to function but may not automatically adjust airflow and temperature as effectively based on sunlight intensity.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1259 to identify the root cause.
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Quick Info
Category
Body
System
Climate Control System
Difficulty
Type
Manufacturer
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