What Does B1238 Mean?
DTC B1238 indicates that a temperature sensor or monitored component within a body control system has exceeded its safe operating temperature threshold. The Body Control Module (BCM) detected an over-temperature condition in a specific circuit or component, which could be related to seat heaters, mirror heaters, window motors, door lock actuators, or other electrically-heated or motor-driven body components. This is a manufacturer-specific code, so the exact component varies by vehicle make and model.
Common Causes
35%
Faulty heated seat element or control module with internal short causing excessive current draw and heat generation
25%
Defective mirror heater element or circuit with short to ground creating thermal overload
20%
Window motor or door lock actuator binding mechanically causing excessive amperage draw and overheating
15%
Corroded or high-resistance wiring connections causing localized heating at connection points
5%
Failed temperature sensor providing false over-temperature readings to BCM
Diagnostic Steps
1
Step 1: Review freeze frame data and identify which specific body control circuit reported the over-temperature fault (heated seats, mirrors, windows, locks). Use the scan tool to access BCM live data and monitor temperature readings for the affected circuit.
2
Step 2: Perform visual inspection of the suspected component (seat heater, mirror, window motor, etc.) and associated wiring harness for signs of heat damage, melted insulation, discolored connectors, or burnt smell indicating thermal stress.
3
Step 3: Using a digital multimeter, measure the current draw of the affected component during operation. Compare readings against manufacturer specifications (typically 3-8 amps for seat heaters, 2-5 amps for mirrors). Excessive amperage indicates component failure or mechanical binding.
4
Step 4: Check resistance of heating elements or motor windings using an ohmmeter with component disconnected. Heated seat elements typically read 1-3 ohms per pad; significantly lower readings indicate short circuits causing overheating.
5
Step 5: Inspect all connectors and ground points in the affected circuit for corrosion, loose pins, or high resistance. Measure voltage drop across connections under load (should be less than 0.1V); excessive drop indicates poor connection causing localized heating.
6
Step 6: If all components and wiring test normal, test the temperature sensor itself (if applicable) by measuring its resistance at various temperatures and comparing to specifications. Replace the faulty component, clear codes, and verify proper operation with no temperature warnings during a complete function test.
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
DTC B1238 indicates that a temperature sensor or monitored component within a body control system has exceeded its safe operating temperature threshold. The Body Control Module (BCM) detected an over-temperature condition in a specific circuit or component, which could be related to seat heaters, mi...
The most common cause of B1238 (Over Temperature Fault) is: Faulty heated seat element or control module with internal short causing excessive current draw and heat generation
Typical repair costs for B1238 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
While not immediately critical to vehicle operation, continued use of an overheating component poses fire risk and may cause permanent damage to interior components or wiring. The affected feature should not be used until diagnosed and repaired, but the vehicle can be driven safely if the overheating circuit is deactivated.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1238 to identify the root cause.
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Quick Info
Category
Body
System
Body Control System
Difficulty
Type
Manufacturer
Recommended Tools
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