Code
B1520
Other
B — Body
Hood Switch Circuit Open
AI status
Completed
Completed
100%
Causes
- Broken or disconnected hood switch connector
- Damaged wiring harness (open circuit) between hood switch and BCM
- Corroded or bent connector pins
- Failed hood position switch
- Blown fuse or loss of reference/power to the circuit
- Intermittent connection or water intrusion
Symptoms
- Hood-open/ajar warning lamp or message on dash
- Interior lights or dome may stay on (battery drain risk)
- Alarm/immobilizer may not arm or may trigger incorrectly
- Hood-open indicator remains active after hood closed
- DTC stored; possible related communication alerts
What to check
- Read and record DTC(s) and freeze frame with a scan tool; note related codes
- Visually inspect hood switch, latch area, connector and wiring for damage or corrosion
- Check for proper connector seating at the hood latch and BCM
- Inspect fuses and power/ground for the body control module circuit
- Probe the switch connector with a multimeter or probe to check for signal and reference voltage
- Perform wiggle test while monitoring live data to look for intermittent changes
Signal parameters
- Typical switch behavior: closed = low resistance (near 0 Ω) between terminals; open = infinite resistance
- Expected signal voltage depends on vehicle: often 0 V (ground) when closed and a pull‑up voltage (~5 V) when open, or 12 V/ground depending on design. Verify against vehicle wiring diagram
- Open-circuit condition: no continuity to BCM or no change in signal when operating the switch
- Intermittent: fluctuating or pulsing voltage when manipulating harness or switch
Diagnostic algorithm
- Verify the B1520 code with a scan tool and clear then retest to confirm it returns.
- Perform a visual inspection of the hood latch/switch, connector and wiring for damage, corrosion, or water intrusion. Repair obvious physical damage.
- With ignition on, monitor the hood-switch input in live data while opening/closing the hood to confirm no signal change.
- Backprobe the switch connector: check for expected reference voltage (5 V or 12 V) and signal behavior when the switch is actuated. If no reference, trace to fuse/BCM.
- Check continuity between the switch and the BCM connector; repair any open circuits. Repair chafed wires, broken conductors, or poor grounds.
- If wiring and connectors are good, bench-test or replace the hood switch and retest for correct operation.
- After repairs, clear codes, cycle ignition and hood several times, then verify the code does not return and the hood indicator behaves correctly.
- If intermittent or communication errors persist, inspect BCM connectors and related modules for faults and perform module communication checks.
Likely causes
- Disconnected or corroded hood switch connector at the latch
- Chafed or broken wire where the harness flexes (hood hinge area)
- Failed hood switch due to wear or contamination
- Poor ground or missing pull‑up/pull‑down resistor at BCM/input
Fault status
Status
B1520 — Hood Switch Circuit Open: Hood position switch signal missing or open circuit detected.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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