What Does B1387 Mean?
This code indicates that the Body Control Module (BCM) or Powertrain Control Module (PCM) has detected an open circuit in the oil temperature sensor circuit. An open circuit means there is no electrical continuity, typically caused by a disconnected sensor, broken wire, or failed sensor internal element. The module monitors oil temperature to protect the engine or transmission and optimize performance, but is receiving no signal from the sensor.
Common Causes
45%
Faulty oil temperature sensor with internal open circuit or corroded connector terminals
30%
Broken or severed wiring between oil temperature sensor and control module
15%
Loose, disconnected, or damaged sensor connector with poor pin contact
10%
Failed control module internal circuit for oil temperature monitoring
Diagnostic Steps
1
Step 1: Perform visual inspection of the oil temperature sensor and its connector for obvious damage, disconnection, corrosion, or bent pins. Check sensor mounting for physical damage or oil leaks that may have affected the sensor.
2
Step 2: Using a digital multimeter, measure resistance across the oil temperature sensor terminals with connector disconnected. Compare readings to manufacturer specifications (typically 200-5000 ohms depending on temperature). An infinite reading confirms sensor open circuit.
3
Step 3: Inspect wiring harness from sensor to control module for chafing, cuts, or breaks. Check continuity of each wire in the circuit using a multimeter with sensor disconnected. Resistance should be less than 1 ohm for intact wiring.
4
Step 4: Check for proper ground circuit by measuring voltage drop between sensor ground and battery negative with key on. Should be less than 0.1 volts. Verify reference voltage at sensor connector (typically 5V) from control module.
5
Step 5: If all wiring and connections test good, substitute a known-good oil temperature sensor and clear codes. Road test and monitor live data to verify proper temperature readings and confirm repair.
Estimated Repair Cost
$75 - $350
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) or Powertrain Control Module (PCM) has detected an open circuit in the oil temperature sensor circuit. An open circuit means there is no electrical continuity, typically caused by a disconnected sensor, broken wire, or failed sensor internal ele...
The most common cause of B1387 (Oil Temperature Sensor Circuit Open) is: Faulty oil temperature sensor with internal open circuit or corroded connector terminals
Typical repair costs for B1387 range from $75 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Generally safe to drive short distances, but the vehicle cannot monitor oil temperature which may lead to overheating damage if oil temperature rises excessively. Repair within a few days to prevent potential engine or transmission damage from undetected high oil temperatures.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1387 to identify the root cause.
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Quick Info
Category
Body
System
Engine Management / Transmission Control
Difficulty
Type
Manufacturer
Recommended Tools
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