Oil Level Switch Circuit Short to Ground
The B1308 code indicates that the Engine Control Module (ECM) or Body Control Module (BCM) has detected a short to ground in the oil level switch signal circuit. The switch is normally closed when oil level is low and open when level is correct, sending a voltage signal to the module. A short to ground pulls the signal to 0V, causing the system to misinterpret this as a critically low oil level.
1. Commonly Affected Makes
2. Most Common Causes
- Oil level switch (sensor) internally shorted to ground
- Signal wire insulation damaged, chafed, or pinched, contacting engine or chassis ground
- Sensor connector corroded, loose, or with bent terminals causing ground contact
- Internal ECM/BCM input driver failure (rare)
3. Symptoms You Will Notice
- Oil warning light illuminated on dashboard
- Possible engine performance issues or limp mode activation
4. Step-by-Step Diagnosis
Verify oil level on dipstick; if normal, proceed with electrical diagnosis
Inspect oil level switch connector for corrosion, damage, or loose terminals
Check signal wire for shorts to ground using a multimeter
Test switch operation by measuring resistance between signal and ground; replace if shorted
If wiring and switch are good, suspect ECM/BCM fault and perform module self-test
5. Frequently Asked Questions
Is it safe to drive?▼
No, driving with this code is not recommended as it may indicate a real low oil level or cause incorrect oil level readings, potentially leading to engine damage.
How much does it cost to fix?▼
Repair costs typically range from $100 to $400, depending on whether the switch, wiring, or module needs replacement.