What Does B1308 Mean?
This diagnostic trouble code indicates that the Body Control Module (BCM) has detected an abnormal electrical condition in the oil level switch circuit. Specifically, the circuit voltage has dropped below the expected range, suggesting that the signal wire is shorted to ground or experiencing excessive resistance to ground. This prevents the BCM from accurately monitoring engine oil level status.
Common Causes
40%
Damaged or chafed wiring harness causing short to ground between oil level sensor and BCM
30%
Failed oil level switch/sensor with internal short to ground
20%
Corroded or damaged connector terminals at oil level sensor allowing moisture intrusion and ground fault
10%
BCM internal circuit failure or water damage causing false short to ground detection
Diagnostic Steps
1
Step 1: Perform visual inspection of the oil level switch/sensor connector and wiring harness from sensor to BCM, looking for damaged insulation, chafing against metal components, pinched wires, corrosion, or signs of moisture intrusion
2
Step 2: Disconnect the oil level switch connector and measure resistance between the signal wire terminal (at harness side) and chassis ground using a digital multimeter - should read infinite resistance (open circuit). Any continuity indicates a short to ground in the wiring
3
Step 3: If wiring tests good, measure resistance across the oil level switch terminals with switch disconnected - compare to manufacturer specifications (typically several hundred to several thousand ohms). Near-zero resistance indicates internal sensor short
4
Step 4: If both wiring and sensor test good, check for proper ground connection at BCM and verify BCM connector terminals are not corroded or damaged. Perform voltage drop test on ground circuits
5
Step 5: Clear the code, reconnect all components, and operate vehicle through normal driving cycle. Monitor for code recurrence using scan tool live data while observing oil level switch status
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
This diagnostic trouble code indicates that the Body Control Module (BCM) has detected an abnormal electrical condition in the oil level switch circuit. Specifically, the circuit voltage has dropped below the expected range, suggesting that the signal wire is shorted to ground or experiencing excess...
The most common cause of B1308 (Oil Level Switch Circuit Short To Ground) is: Damaged or chafed wiring harness causing short to ground between oil level sensor and BCM
Typical repair costs for B1308 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this is a monitoring circuit fault rather than an actual oil level problem. However, you will lose the ability to be warned of low engine oil conditions, so manually check oil level regularly until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1308 to identify the root cause.
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Quick Info
Category
Body
System
Engine Monitoring System
Difficulty
Type
Manufacturer
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