B1574: Left Rear Door Sensor Short to Ground
The B1574 code indicates that the left rear door ajar sensor circuit is shorted to ground. This code is specific to Ford and its associated brands. The body control module (BCM) or generic electronic module (GEM) monitors the door switch status via voltage signals. When the door is closed, the circuit typically shows a reference voltage; when open, the voltage changes. A short to ground keeps the voltage permanently low, which the module interprets as a constant door-open condition or a circuit fault, depending on the diagnostic logic. This can trigger dashboard warnings, affect interior lighting, mirror folding, or prevent the alarm from arming properly. Diagnosis should focus on the left rear door switch, its wiring harness, and connections at the B-pillar or door jamb, areas prone to flex damage and corrosion.
1. Commonly Affected Makes
2. Most Common Causes
3. Symptoms You Will Notice
- Door ajar warning light on the dashboard
- Interior lights staying on or not working properly
- Power mirror folding malfunction
- Alarm system fails to arm
4. Step-by-Step Diagnosis
Inspect the left rear door switch for physical damage or corrosion.
Check the wiring harness in the door jamb for cuts, chafing, or broken wires.
Test the signal wire for continuity to ground; if shorted, isolate the fault.
Examine the switch connector for bent or corroded pins.
If all else is good, test the BCM/GEM for internal faults.
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but you may experience minor electrical issues like interior lights staying on or alarm problems. It is recommended to diagnose and repair soon to avoid battery drain.
How much does it cost to fix?▼
Repair costs typically range from $100 to $300, depending on whether the switch, wiring, or module needs replacement. Labor is usually 1-2 hours.