B1340 — Chime Input Request Circuit Short To Ground #

Note: The code label may vary depending on the vehicle manufacturer.

• B1340 – Chime Input Request Circuit Shorted to Ground (Ford, Lincoln, Mercury)
• B1340 – Warning Chime Input Circuit Short to Ground (Mazda)
• B1340 – Chime Request Circuit Low (General Motors)

Summary of code B1340 #

The B1340 Diagnostic Trouble Code (DTC) indicates a problem in the Chime Input Request Circuit, specifically a short to ground condition. This circuit is responsible for relaying signals to the vehicle’s chime or warning buzzer system, which alerts the driver to specific conditions—such as door ajar, seatbelt unbuckled, or headlights left on. When a “short to ground” is detected, it means an unintended connection is sending voltage directly to ground, disrupting normal operation. This could lead to a chime that won’t sound when it should, or one that stays on constantly. Understanding and diagnosing this code is essential for restoring proper warning functions in your vehicle and ensuring you’re alerted to important safety issues.

Common symptoms for code B1340 #

Drivers and technicians might notice a range of unusual behaviors from the chime or warning system when code B1340 is present. Sometimes, the chime may stay silent when it should be alerting you, like a watchman asleep at his post. Other times, it may sound incessantly, even when there’s no issue, much like a car alarm going off for no reason. You may also see a warning light on your dashboard. Typical symptoms include:

• Chime does not sound when a warning condition exists (e.g., door open, key in ignition, seatbelt off)
• Chime sounds continuously or erratically, regardless of vehicle conditions
• Warning indicator light illuminated on the dashboard
• Other warning systems may malfunction or become inoperative

Probable causes for code B1340 #

While a short to ground sounds technical, it’s often a matter of a wire touching metal where it shouldn’t, or a component failing internally. The most frequent causes, ranked by likelihood, are:

1. Damaged or chafed wiring in the chime input circuit, touching the vehicle body (ground)
2. Faulty chime module or warning buzzer with internal shorting
3. Corroded or loose electrical connectors at the chime assembly or related harnesses
4. Water intrusion in the cabin junction box or under-dash area causing shorts
5. Defective switch (e.g., door ajar, seatbelt, ignition) sending false signals
6. Incorrect aftermarket accessory wiring interfering with the chime circuit

Step-by-step diagnostics for code B1340 #

Diagnosing a “short to ground” requires patience—think of it as tracking down a hidden leak in your home’s plumbing. The following process will help you pinpoint the issue:

• Verify the code with a professional scan tool and clear any stored codes. See if B1340 returns immediately.
• Consult OEM wiring diagrams to identify all components and connectors on the chime input circuit.
• Visually inspect wiring harnesses under the dashboard and near the chime module for signs of chafing, pinching, or exposed wires.
• Check connectors for corrosion, bent pins, or moisture. Ensure all connectors are fully seated.
• Test the circuit with a digital multimeter: disconnect the chime module and check for continuity between the chime input wire and ground. Zero resistance indicates a short.
• Isolate affected sections by unplugging switches (door, seatbelt, ignition) one at a time to see if the short clears. This localizes the fault.
• Inspect the chime module itself for internal faults by substituting with a known-good unit if possible.

Possible repairs for code B1340 #

Once you’ve tracked down the culprit, repairs should focus on restoring the integrity of the chime input circuit. Common solutions include:

• Repairing or replacing damaged wiring (repair with solder and shrink tubing; reroute harness if necessary)
• Replacing faulty chime module or warning buzzer if found internally shorted
• Cleaning and securing electrical connectors to remove corrosion or moisture
• Replacing defective switches (door ajar, seatbelt, ignition) if they’re causing false inputs
• Correcting or removing improper aftermarket accessory wiring
• Sealing areas prone to water intrusion to prevent future shorts

Is it safe to drive with code B1340? #

Yes, but with limitations. Your vehicle will generally remain drivable with B1340 present, as it doesn’t directly affect engine or transmission operation. However, you may miss important warnings about safety issues (like an open door or unbuckled seatbelt), which could put you and your passengers at risk. If the chime sounds constantly, it can also be distracting. For safety and peace of mind, it’s best to address this code promptly.

Most commonly affected vehicles by code B1340 #

While B1340 is most commonly associated with certain Ford, Lincoln, and Mercury models, it can appear in a range of vehicles—especially those sharing similar chime/warning architectures. The following vehicles are known to be frequently affected:

• Ford F-150 (2004–2014)
• Ford Explorer (2002–2010)
• Lincoln Navigator (2003–2014)
• Mercury Mountaineer (2002–2010)
• Mazda Tribute (2001–2008)
• Chevrolet Silverado (with GM variant of the code)

Common mistakes and best practices for code B1340 #

It’s easy to fall into a few diagnostic traps with this code. Here’s what to watch out for—and some tips to get it right the first time:

• Don’t just replace the chime module without checking wiring—most faults are wiring-related.
• Avoid ignoring subtle wiring damage under the dash, especially in areas prone to foot traffic or previous repairs.
• Check for aftermarket alarms or remote starters tied into chime circuits—they often introduce shorts.
• Use OEM wiring diagrams for accurate tracing; guessing leads to missed faults.
• Never bypass the chime system—you’ll lose critical safety warnings.

Quick FAQ for code B1340 #

Here are some rapid-fire answers to the questions technicians and drivers ask most:

• Q: Will this code cause my vehicle to fail inspection?
  A: Not usually, since it’s a body/electrical code, but some states require all warning systems to work for safety checks.
• Q: Can I clear the code and make it go away?
  A: You can clear it, but if the underlying fault isn’t fixed, it will return as soon as the system rechecks itself.
• Q: Is this a common DIY repair?
  A: If you’re comfortable with wiring and have a multimeter, you can try—just take care to avoid damaging the harness further.