What Does B1949 Mean?
This code indicates the climate control module has detected an abnormal short-to-ground condition in the water temperature sensor circuit used by the HVAC system. The sensor monitors coolant or heater core temperature to regulate cabin heating performance. The control module detected voltage below the normal operating range, indicating the signal wire is shorted to ground or the sensor has failed internally.
Common Causes
40%
Damaged or chafed wiring harness causing short to ground between sensor and climate control module
35%
Failed water temperature sensor with internal short to ground
15%
Corroded or water-damaged connector terminals at sensor or control module creating ground path
10%
Failed climate control module with internal circuit fault
Diagnostic Steps
1
Step 1: Perform visual inspection of the water temperature sensor location (typically at heater core or coolant line) checking for coolant leaks, corrosion, damaged connectors, or obvious harness damage
2
Step 2: Disconnect the water temperature sensor connector and measure resistance across sensor terminals using a digital multimeter - compare readings to manufacturer specifications (typically 2-5k ohms at room temperature for thermistors)
3
Step 3: With sensor disconnected, check for continuity between the sensor signal wire at the harness connector and known good ground - any continuity indicates wiring short to ground requiring harness repair
4
Step 4: If wiring tests good, inspect connector pins for corrosion, bent terminals, or moisture intrusion and clean/repair as needed, then retest
5
Step 5: If sensor and wiring are confirmed good, suspect climate control module internal fault - verify by substituting known good module or checking module ground circuits for integrity
6
Step 6: Clear codes, reinstall all components, and verify proper operation through full climate control function test including temperature changes and monitoring sensor data via scan tool
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
This code indicates the climate control module has detected an abnormal short-to-ground condition in the water temperature sensor circuit used by the HVAC system. The sensor monitors coolant or heater core temperature to regulate cabin heating performance. The control module detected voltage below t...
The most common cause of B1949 (Climate Control Water Temperature Sensor Circuit Short To Ground) is: Damaged or chafed wiring harness causing short to ground between sensor and climate control module
Typical repair costs for B1949 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive with this code. The primary impact is reduced climate control accuracy and potential loss of automatic temperature regulation, resulting in inadequate cabin heating or cooling performance but no safety risk.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1949 to identify the root cause.
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Quick Info
Category
Body
System
Climate Control System
Difficulty
Type
Manufacturer
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