B1520 — Hood Switch Circuit Open #

The wording of this code may vary depending on the manufacturer. Always check your OEM’s official documentation for the exact description related to your vehicle.

Known wording variations for B1520:

• Hood Switch Circuit Open (generic/OEMs: Ford, GM, Toyota)
• Bonnet Switch Open Circuit (Jaguar, Land Rover)
• Engine Hood Switch Signal Circuit Open (Hyundai, Kia)
• Hood Ajar Switch Circuit Open (Chrysler, Jeep, Dodge)

Summary for code B1520 #

B1520 is a diagnostic trouble code (DTC) indicating that the vehicle’s hood switch circuit has an open connection. The hood switch is a sensor that detects whether the hood (also called the bonnet) is open or closed, primarily for security and safety systems. When the Engine Control Module (ECM) or Body Control Module (BCM) detects an open circuit — meaning it cannot detect the switch — it triggers this code. This is commonly related to alarms, remote start systems, or underhood service safety features. While not a direct engine or drivability fault, this code should be addressed to ensure vehicle security systems function correctly and to avoid unwanted warning lights or features being disabled.

Common symptoms for code B1520 #

A vehicle with a B1520 code may not exhibit any obvious drivability problems, but several noticeable symptoms can occur. These are mostly linked to the vehicle’s security, alarm, and remote start systems. Here’s what you might observe:

• Security system warning light illuminated
• Alarm system not arming or disarming properly
• Remote start system disabled
• Hood ajar warning message or indicator
• Possible chime or alert indicating open hood
• In some cases, no visible symptom (code found only during scan)

Probable causes for code B1520 #

Most B1520 faults boil down to issues with the hood switch circuit. The problem can originate from the switch itself, the wiring, or sometimes the control module. Here are the most common root causes, ranked by likelihood:

1. Faulty hood switch (corroded, mechanically stuck, or damaged)
2. Broken, cut, or corroded wiring between the switch and the control module
3. Unplugged or loose hood switch connector
4. Faulty or damaged hood latch assembly (if the switch is integrated)
5. Water intrusion or corrosion in the switch area or connector
6. Defective Body Control Module (BCM) (rare)

Step-by-step diagnosis for code B1520 #

Diagnosing B1520 requires a systematic approach. The goal is to pinpoint whether the open circuit is due to the switch, wiring, or module. Here’s a proven method:

• Step 1: Read all DTCs with a scan tool and record freeze frame data.
• Step 2: Inspect the hood switch for physical damage, corrosion, or misalignment.
• Step 3: Check the hood switch connector for tightness and signs of water or corrosion.
• Step 4: Use a multimeter to test for continuity across the hood switch. With the hood closed, the circuit should be closed (low resistance).
• Step 5: Inspect wiring from the switch to the BCM for breaks, cuts, or corrosion. Repair as needed.
• Step 6: If switch and wiring test good, check for proper signal at the BCM pin (consult wiring diagram for your OEM).
• Step 7: If everything else checks out, suspect a BCM fault — rare, but possible.

Possible repairs for code B1520 #

Once the cause is pinpointed, repairs are usually straightforward and often inexpensive. Here are the recommended fixes, mapped to the typical causes:

• Replace the hood switch if found faulty
• Repair or replace damaged wiring between switch and module
• Clean or repair hood switch connector for corrosion or looseness
• Replace the hood latch assembly if the switch is integrated and not serviceable separately
• Address water leaks that may have caused corrosion
• Replace the Body Control Module (BCM) only if all other causes are eliminated

Is it safe to drive with code B1520? #

Yes, you can generally drive with this code — but with some limitations. The B1520 code rarely affects engine performance or vehicle safety directly. However, it may disable security or remote start systems and could trigger persistent warning lights or chimes. If your vehicle relies on the hood switch for additional safety features (such as disabling the engine when the hood is open), those may not work correctly. It’s best to address the issue soon to restore full system functionality and avoid nuisance alarms.

Vehicles most commonly affected by B1520 #

B1520 is a generic code, but it appears more frequently on certain models and brands, especially those with advanced security or remote start features. Based on service data, these vehicles see this code more often:

• Ford F-Series (F-150, F-250, etc.)
• Chevrolet Silverado, GMC Sierra
• Toyota Camry, Corolla, RAV4
• Hyundai Sonata, Tucson
• Jeep Grand Cherokee, Wrangler
• Jaguar XF, XE, XJ
• Land Rover Discovery, Range Rover

Common mistakes & best practices for B1520 #

Technicians and DIYers sometimes misdiagnose or overlook simple issues with B1520. Here’s what to watch out for — and what to do right:

• Replacing the switch before checking wiring — always inspect and test wiring and connectors first
• Ignoring signs of water intrusion — hood switches are exposed and prone to corrosion
• Forgetting to check the latch assembly — some switches are built into the latch, not separate
• Neglecting to clear codes after repair — always clear the DTC and test for proper operation
• Assuming a module fault too soon — BCM failure is rare; exhaust all other causes first

Express FAQ for code B1520 #

Still have questions about B1520? Here are quick answers to the most common concerns:

• Q: Will B1520 cause my car to stall or not start?
  A: No. This code is not related to direct engine control. However, if your vehicle uses the hood switch for remote start, that function may not work until the issue is repaired.
• Q: Can I bypass the hood switch to clear the code?
  A: While technically possible, bypassing the switch is not recommended. It can compromise your security system and may violate warranty or safety guidelines. Always repair the root cause.
• Q: How much does it typically cost to fix a B1520 code?
  A: Most repairs involve replacing the hood switch or repairing wiring, which are usually low-cost parts and labor items. If a BCM replacement is needed, costs can be significantly higher.

If you need more model-specific support, always refer to your OEM’s official repair manual or consult a qualified technician.