What Does B1948 Mean?
This code indicates that the Body Control Module (BCM) or Climate Control Module has detected an electrical fault in the water temperature sensor circuit used by the HVAC system. This sensor monitors coolant or heater core temperature to regulate cabin heating performance. The fault could be an open circuit, short circuit, or sensor resistance value outside the expected range.
Common Causes
40%
Faulty climate control water temperature sensor with internal failure or drift out of specification
30%
Damaged, corroded, or loose wiring/connectors in the sensor circuit between sensor and control module
20%
Corroded or poor ground connection for the climate control temperature sensor circuit
10%
Failed climate control module or BCM with internal circuit fault
Diagnostic Steps
1
Step 1: Perform a visual inspection of the water temperature sensor location (typically mounted in heater core inlet/outlet hose or near HVAC housing), checking for visible damage, coolant leaks, corroded connectors, or broken wires
2
Step 2: Disconnect the water temperature sensor connector and measure sensor resistance with a multimeter (typical NTC thermistor sensors range from 2000-3000 ohms at room temperature, 200-400 ohms at 200°F, consult manufacturer specs); compare readings to specification
3
Step 3: With sensor disconnected, check wiring harness side connector for 5V reference voltage (or 12V depending on system) and continuity to ground on the appropriate pins; check for short to ground or voltage on signal wire
4
Step 4: Inspect and test the ground circuit by measuring resistance from sensor ground pin to vehicle chassis ground (should be less than 1 ohm); clean and secure ground connections if resistance is high
5
Step 5: If sensor and wiring test normal, substitute a known-good sensor or use a decade box to simulate sensor resistance values while monitoring live data to determine if the control module responds appropriately
6
Step 6: Clear codes, test drive with various climate control settings, and monitor for code recurrence; verify proper HVAC temperature control operation after repairs
Estimated Repair Cost
$150 - $450
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) or Climate Control Module has detected an electrical fault in the water temperature sensor circuit used by the HVAC system. This sensor monitors coolant or heater core temperature to regulate cabin heating performance. The fault could be an open...
The most common cause of B1948 (Climate Control Water Temperature Sensor Circuit Failure) is: Faulty climate control water temperature sensor with internal failure or drift out of specification
Typical repair costs for B1948 range from $150 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive as this code only affects climate control temperature regulation and passenger comfort. The heating system may not function optimally, but there is no immediate safety risk or damage concern.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1948 to identify the root cause.
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Quick Info
Category
Body
System
Climate Control / HVAC System
Difficulty
Type
Manufacturer
Recommended Tools
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