What Does B1391 Mean?
This code indicates that the Body Control Module (BCM) has detected an electrical fault in the engine oil level sensor circuit. The oil level switch monitors the engine oil level and sends a signal to the BCM; when the circuit voltage is out of range (open, short to ground, or short to power), this code sets. This is typically a monitoring circuit issue rather than an actual low oil condition, though oil level should still be verified.
Common Causes
45%
Faulty oil level sensor/switch with internal circuit failure or contamination
30%
Damaged, corroded, or disconnected wiring harness connector at oil level sensor
15%
Wiring harness damage, chafing, or short circuit between sensor and BCM
10%
Body Control Module (BCM) internal circuit failure
Diagnostic Steps
1
Step 1: Verify actual engine oil level using dipstick and inspect for proper oil quality. Check oil level sensor location (typically in oil pan) for physical damage, oil leaks, or loose mounting
2
Step 2: Locate and inspect the oil level sensor electrical connector for corrosion, pushed-out pins, moisture, or damage. Disconnect connector and inspect both sensor and harness side terminals
3
Step 3: Using a digital multimeter, measure resistance across oil level sensor terminals with connector disconnected (typical range 200-5000 ohms depending on manufacturer). Compare to factory specifications if available
4
Step 4: Check for voltage supply at the sensor harness connector with ignition on (typically 5V or 12V reference). Verify ground circuit continuity to BCM using multimeter (should be less than 1 ohm)
5
Step 5: If wiring and voltage supply are correct, substitute a known-good oil level sensor or monitor live data while manipulating sensor to confirm sensor failure
6
Step 6: Clear codes, perform a test drive or key cycle, and verify the code does not return. Monitor oil level sensor data in live scan tool parameters to confirm proper operation
Estimated Repair Cost
$120 - $450
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) has detected an electrical fault in the engine oil level sensor circuit. The oil level switch monitors the engine oil level and sends a signal to the BCM; when the circuit voltage is out of range (open, short to ground, or short to power), this ...
The most common cause of B1391 (Oil Level Switch Circuit Failure) is: Faulty oil level sensor/switch with internal circuit failure or contamination
Typical repair costs for B1391 range from $120 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is generally safe to drive as this is a sensor circuit fault, not necessarily a low oil condition. However, manually verify oil level immediately as you will not have warning system protection if oil level actually drops low.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1391 to identify the root cause.
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Quick Info
Category
Body
System
Engine Monitoring/Body Control System
Difficulty
Type
Manufacturer
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