B1520 — Hood Switch Circuit Open

What is the most common cause of B1520?

The most common causes are: damaged wiring in door jambs or wet areas, blown fuse or failed relay, corroded or loose connectors.

How much does it cost to fix B1520?

Replace the switch or actuator — $120–$450; BCM repair or replacement — $300–$900; Repair wiring or connectors — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Will B1520 clear itself?

Sometimes B1520 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What does OBD2 code B1520 mean?

OBD2 code B1520 flags a problem with the body electrical system (hood switch circuit open). The car is usually drivable while you plan the repair. Common culprits: damaged wiring in door jambs or wet areas, blown fuse or failed relay, corroded or loose connectors.

How do I diagnose B1520 myself?

Start with a scan: confirm B1520, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the hood switch, and verify the suspect component against live data before buying parts.

The hood switch on your vehicle does more than just trigger a dashboard light when the hood is open. It's part of the body electrical network that manages systems like the alarm, interior lighting, and sometimes even the starter interlock. When the powertrain control module or body control module detects that the hood switch circuit has lost its ground reference or cannot complete a proper electrical path, it logs OBD2 code B1520.

B1520 is classified as a "circuit open" fault, which simply means the electrical loop the module expects to see is broken somewhere. The module itself isn't damaged in most cases—it's simply unable to read a valid signal from the switch. This type of code typically requires the fault to appear under specific operating conditions on two or more consecutive drive cycles before the check engine light or body warning light activates.

The freeze frame data stored alongside B1520 is valuable diagnostic information. It captures the engine operating conditions—RPM, load, temperature, and vehicle speed—at the exact moment the fault was detected. Reproducing those same conditions during testing helps confirm whether the problem is still active or was a one-time event.

Common symptoms of B1520

• The malfunction indicator lamp or body control warning light illuminates on the instrument cluster
• Engine performance remains unaffected in most vehicles
• The affected function—interior lighting, power locks, alarm system, or remote start—operates intermittently or stops working entirely
• The hood ajar indicator may stay illuminated or fail to illuminate when the hood is opened
• Security system may behave erratically or fail to arm/disarm properly
• In rare cases, the starter may be prevented from engaging if the hood switch serves as an interlock

What causes B1520?

• Internally open or failed hood ajar switch
• Broken wire in the hood switch harness from repeated flexing at the hinge area
• Connector unplugged, backed-out terminal, or significant corrosion at the connector
• Blown fuse or failed relay feeding the hood switch circuit
• Wiring damaged by moisture intrusion, especially in door jambs or under the hood
• Loose or corroded ground connection for the body control module
• Body control module internal failure or software calibration issue
• Chafed wiring from contact with sharp metal edges in the engine bay

How to diagnose B1520

1. Connect an OBD2 scanner and confirm B1520 is stored, then record all freeze frame data—this shows the exact conditions when the module detected the fault and guides your test plan.
2. Pull any additional stored codes from all modules; related body codes often expose the real root cause faster than testing the hood switch circuit alone.
3. With the vehicle safely supported, perform a hands-on visual inspection of the hood switch wiring and connectors, looking for broken insulation, corrosion buildup, and signs of water entry.
4. Use a digital multimeter to perform end-to-end continuity checks on the hood switch circuit, paying special attention to areas where the harness flexes during hood operation—fluctuating readings indicate intermittent opens.
5. If your scan tool supports data streaming, monitor the hood switch PID while manually operating the hood latch mechanism and observe whether the signal responds correctly.
6. Clear B1520, complete a full drive cycle that recreates the freeze frame conditions, and verify the code does not return before declaring the repair complete.

How to fix B1520

Address the most common and inexpensive failures before considering major component replacement:

• Hood switch or hood ajar sensor replacement: $120–$450
• Body control module repair or replacement: $300–$900
• Wiring repair or connector replacement: $80–$250

How much does it cost to fix B1520?

The actual repair cost for B1520 depends entirely on which component failed. Here are typical parts-and-labor scenarios at independent repair shops in the United States: replacing a faulty hood switch typically runs $120 to $450 depending on vehicle make and model accessibility. If the body control module is diagnosed as the culprit, expect to pay $300 to $900 for repair service or replacement unit plus programming. Wiring harness repairs or connector replacement generally cost $80 to $250 depending on the extent of the damage and labor time required.

Across all scenarios, fixing B1520 typically falls between $80 and $900. The majority of cases involve either a simple switch replacement or a wiring connector issue on the lower end of that range. An accurate electrical diagnosis before purchasing parts always saves money—the BCM replacement scenario is the least common root cause and should only be pursued after cheaper possibilities are ruled out.

Can you drive with B1520?

Generally safe to operate—the powertrain is unaffected by this body electrical fault. Exercise caution if the hood switch controls exterior lighting or windshield wipers, as these safety features may not function properly during inclement weather. Additionally, some vehicles tie the hood switch to the security system; a malfunction in this circuit could leave the car unsecured. Address B1520 at your earliest convenience even if the vehicle seems drivable.

Related OBD2 codes

• B1500: Lamp Turn Signal Left Circuit Open
• B1501: Lamp Turn Signal Left Circuit Short To Battery
• B1502: Lamp Turn Signal Left Circuit Short To Ground
• B1503: Lamp Turn Signal Right Circuit Failure
• B1504: Lamp Turn Signal Right Circuit Open
• B1505: Lamp Turn Signal Right Circuit Short To Battery