B1359 — Ignition Run/Acc Circuit Failure #

The code label may vary depending on the vehicle manufacturer.

• Ignition Run/Accessory Circuit Failure (Ford)
• Ignition Switch Run or ACC Circuit Fault (GM/Chevrolet)
• Ignition Run/ACC Output Malfunction (Toyota)

Summary of the B1359 Code #

The B1359 DTC (Diagnostic Trouble Code) identifies a malfunction in the electrical pathway that controls the ignition “Run” and “Accessory” (ACC) positions. This circuit is responsible for supplying power to essential vehicle components when the key is turned to these positions. If the control module (often the Body Control Module, or BCM) detects a voltage outside the expected range or a break in the circuit, it triggers this code. The issue can disrupt the operation of electrical systems like the radio, dashboard lights, or even engine control. While this may not always prevent the engine from starting, it can compromise comfort and safety features. Prompt diagnosis and repair are recommended to avoid further electrical complications.

Common Symptoms for Code B1359 #

Several signs may alert you to a problem with the Ignition Run/Acc Circuit. These symptoms vary in severity and can affect multiple vehicle functions, since many systems rely on stable power from this circuit. If you notice any of the following, the B1359 code could be present:

• Accessory features (radio, power windows, wipers) don’t work in accessory mode
• Dashboard lights flicker or don’t illuminate when the key is in “Run” or “ACC”
• The engine may not crank or start in certain key positions
• Electrical systems intermittently lose power
• Security or anti-theft warning lights remain on
• Erratic or delayed operation of cluster gauges

Most Probable Causes for Code B1359 #

The B1359 code is most often triggered by issues within the ignition switch circuit or related wiring. Causes can range from simple wear and tear to more complex electrical faults. Here are the most common origins, listed by likelihood:

1. Faulty ignition switch (wear or internal failure)
2. Damaged or corroded wiring in the Run/ACC circuit
3. Loose or poor electrical connections at the ignition switch or body control module
4. Defective body control module (BCM) or similar relay/control unit
5. Blown fuse related to the ignition or accessory circuit
6. Aftermarket remote starter or alarm system interfering with OEM wiring

Step-by-Step Diagnostic for Code B1359 #

Accurate diagnosis is key to resolving B1359 without unnecessary repairs. Use this systematic approach to pinpoint the root cause:

• Verify the code with a scan tool and record freeze-frame data.
• Inspect the ignition switch for wear, heat damage, or loose operation.
• Check all related fuses for continuity and proper amperage.
• Visually examine wiring and connectors from the ignition switch to the BCM for corrosion, pinched wires, or loose terminals.
• Test circuit voltage at the ignition switch “Run” and “ACC” outputs during key cycling.
• Inspect aftermarket devices (alarm, remote start) for improper splices or connections.
• Test the BCM (if equipped) for internal faults using OEM procedures.
• Clear the code and perform a functional test to confirm the repair.

Possible Repairs for Code B1359 #

Once the cause is identified, targeted repairs will restore proper function. These solutions directly address the most common issues behind B1359:

• Replace the faulty ignition switch if internal contacts are worn or inoperative.
• Repair or replace damaged wiring/connectors in the Run/ACC circuit.
• Secure or reseat loose connections at the ignition switch or BCM.
• Replace any blown fuses and investigate underlying causes for fuse failure.
• Remove or correctly rewire aftermarket devices that compromise OEM circuits.
• Replace the BCM if it fails internal circuit tests (as per OEM procedure).

Is It Safe to Drive with Code B1359? #

Driving is limited and not recommended until repairs are made. While some vehicles may continue to run, the loss of accessory or run functions can impact key systems—potentially affecting safety equipment, visibility (wipers, lights), or even the ability to restart the engine. If you experience intermittent power loss or starting issues, avoid driving until the problem is corrected to prevent being stranded or having a sudden loss of function.

Vehicles Most Commonly Affected by Code B1359 #

While B1359 is a “body” code found in many modern vehicles, certain makes and models are more frequently associated with this fault, especially those with complex ignition circuits or high accessory loads. Vehicles with heavy use of remote starters or aftermarket electronics may also be more prone. Common examples include:

• Ford F-Series (F-150, F-250, F-350)
• Chevrolet Silverado and GMC Sierra (especially 2000s models)
• Ford Explorer and Expedition
• GM SUVs (Tahoe, Yukon, Suburban)
• Toyota Camry and Corolla (certain years)

Common Mistakes & Best Practices for Code B1359 #

Misdiagnosis can lead to unnecessary part replacements and recurring issues. Awareness of these pitfalls will help you resolve B1359 quickly and effectively:

• Replacing the ignition switch without inspecting wiring—corroded or damaged wires are equally common culprits.
• Overlooking aftermarket devices that may have altered the factory wiring.
• Ignoring BCM diagnostics—a failing control module can mimic switch or wiring faults.
• Not resetting the code after repairs, which can mask a persistent issue.
• Best Practice: Always perform a thorough visual and voltage check before replacing components.

Express FAQ for Code B1359 #

Here are quick answers to the most frequent questions about this DTC:

• Q: Can a weak battery cause B1359?
  A: Unlikely. B1359 is specific to the ignition Run/ACC circuit and not general battery voltage, but low voltage may worsen symptoms.
• Q: Will clearing the code fix the issue?
  A: No. The code will return unless the underlying circuit fault is addressed.
• Q: Does this code mean my car won’t start?
  A: Not always. Some vehicles may only lose accessory power, but others might not start depending on the nature of the fault.