What Does B1389 Mean?
This code indicates the Body Control Module (BCM) or Powertrain Control Module (PCM) has detected an electrical fault in the oil temperature sensor circuit. The control module is receiving a signal that is out of the expected range—either too high (open circuit), too low (short to ground), or erratic. This prevents accurate monitoring of engine or transmission oil temperature, which is critical for optimal operation and protection strategies.
Common Causes
45%
Faulty oil temperature sensor with internal failure or contamination
30%
Damaged, corroded, or loose wiring connector at the sensor
15%
Broken, chafed, or shorted wiring harness between sensor and control module
10%
Failed control module (BCM/PCM) with internal sensor circuit fault
Diagnostic Steps
1
Step 1: Perform visual inspection of oil temperature sensor and connector for physical damage, corrosion, bent pins, or contamination. Check for proper seating and lock engagement of connector.
2
Step 2: Using a digital multimeter, backprobe the oil temperature sensor connector and measure resistance across sensor terminals with engine cold. Compare readings to manufacturer specifications (typically 2000-10,000 ohms at room temperature for NTC sensors).
3
Step 3: Check for continuity and resistance in the wiring harness between the sensor connector and the control module. Test for short-to-ground, short-to-power, and open circuits on both signal and ground wires.
4
Step 4: If wiring is intact, monitor live sensor voltage data with engine at operating temperature using scan tool. Signal should change smoothly as temperature rises (typically 0.5-4.5V range). Erratic readings indicate sensor failure.
5
Step 5: If sensor and wiring test good, perform voltage supply test at sensor connector with harness disconnected. Verify control module is providing proper reference voltage (typically 5V) on signal wire.
6
Step 6: Replace faulty component (sensor, wiring, or control module based on findings), clear codes, and verify repair by monitoring live data through multiple temperature cycles.
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) or Powertrain Control Module (PCM) has detected an electrical fault in the oil temperature sensor circuit. The control module is receiving a signal that is out of the expected range—either too high (open circuit), too low (short to ground), or errati...
The most common cause of B1389 (Oil Temperature Sensor Circuit Failure) is: Faulty oil temperature sensor with internal failure or contamination
Typical repair costs for B1389 range from $100 to $450, 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 properly monitor oil temperature which may lead to inadequate engine or transmission protection strategies. Extended driving could risk overheating damage if actual oil temperature exceeds safe limits without detection.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1389 to identify the root cause.
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Quick Info
Category
Body
System
Engine Management / Transmission Control System
Difficulty
Type
Manufacturer
Recommended Tools
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