What Does B2381 Mean?
This code indicates the Body Control Module (BCM) or climate control module has detected an open circuit in the heater coolant temperature sensor. This sensor monitors the temperature of coolant flowing through the heater core to optimize cabin heating performance. An open circuit means there is a complete break in the electrical path, preventing the module from receiving any signal from the sensor.
Common Causes
45%
Damaged or broken wiring harness to the heater coolant temperature sensor, including corroded or disconnected connector terminals
35%
Failed heater coolant temperature sensor with internal open circuit
15%
Corroded or loose ground connection for the heater coolant sensor circuit
5%
Failed climate control module or BCM with internal circuit fault
Diagnostic Steps
1
Step 1: Perform visual inspection of the heater coolant temperature sensor location (typically near heater core inlet/outlet). Check for damaged wiring, corroded connections, disconnected connectors, or physical sensor damage. Wiggle connectors and wiring while observing for intermittent signal.
2
Step 2: Disconnect the heater coolant temperature sensor connector and measure resistance across the sensor terminals using a digital multimeter. Compare readings to manufacturer specifications (typically 2000-3000 ohms at room temperature for NTC sensors). Infinite resistance confirms failed sensor.
3
Step 3: With sensor disconnected, inspect connector terminals for corrosion, bent pins, or moisture. Check continuity of both signal and ground wires from sensor connector back to the control module connector using multimeter. Resistance should be less than 1 ohm for each wire.
4
Step 4: Locate and inspect ground connection point for the sensor circuit (consult wiring diagram). Clean ground connection, check for tight connection and verify continuity to battery negative terminal.
5
Step 5: If all wiring and grounds test good but sensor shows infinite resistance, replace heater coolant temperature sensor. If wiring shows open circuit, repair or replace affected harness section and connectors.
6
Step 6: Clear codes, cycle ignition, operate heater system through full temperature range and verify code does not return. Monitor live data for proper sensor temperature readings that increase with heater operation.
Estimated Repair Cost
$75 - $350
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) or climate control module has detected an open circuit in the heater coolant temperature sensor. This sensor monitors the temperature of coolant flowing through the heater core to optimize cabin heating performance. An open circuit means there is a c...
The most common cause of B2381 (Heater Coolant Temp sensor circuit Open) is: Damaged or broken wiring harness to the heater coolant temperature sensor, including corroded or disconnected connector terminals
Typical repair costs for B2381 range from $75 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This code does not affect vehicle safety or drivability. It may result in reduced heater performance or inability to accurately control cabin temperature, but the vehicle can be driven normally until repair is convenient.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2381 to identify the root cause.
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Quick Info
Category
Body
System
Climate Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
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