B1555 — Ignition Run/Start Circuit Failure #

Note: The code description may vary depending on the vehicle manufacturer (OEM). Always refer to your vehicle’s specific service documentation for the most accurate terminology.

• Ignition Run/Start Circuit Failure (General, Ford, GM, Chrysler, Toyota, Nissan)
• Ignition Switch Run/Start Circuit Malfunction (GM)
• Ignition Key On/Start Input Circuit Error (Chrysler)
• Ignition Voltage Run/Start Signal Fault (Toyota, Nissan)

Summary of Code B1555 #

The B1555 code signals a problem within the ignition run/start circuit. This circuit is responsible for delivering power from the ignition switch to essential electrical systems whenever the key is in the RUN or START position. If the circuit fails, the vehicle’s electronic control modules may not receive the correct input, potentially preventing the engine from starting or causing certain functions to become inoperative. This code is typically stored when the OEM’s body control module (BCM) or similar controller detects an abnormal voltage, open, or short in the circuit. Prompt diagnosis is important, as the issue may leave the vehicle inoperable or stuck in a limited-function mode.

Common Symptoms for B1555 #

A faulty ignition run/start circuit can manifest in several ways. Some symptoms are obvious—such as a no-start condition—while others may be more subtle, like intermittent electrical glitches. If you observe any of the following, the B1555 code may be present:

• Engine will not start or crank
• Intermittent starting issues
• Loss of power to accessories (radio, lights, HVAC) in RUN or START positions
• Warning lights illuminated on the dash (such as security or immobilizer icons)
• Erratic behavior of power windows, locks, or other BCM-controlled features
• No communication with certain control modules

Most Likely Causes for B1555 #

The root causes of a B1555 code generally relate to electrical interruptions or faults within the ignition switch circuit. Some issues are more common than others, and the order below reflects their frequency:

1. Faulty ignition switch (mechanical or electrical failure)
2. Damaged, corroded, or loose wiring/connectors in the ignition run/start circuit
3. Blown fuse or faulty relay in the ignition circuit
4. Defective body control module (BCM) or immobilizer module (rare)
5. Aftermarket alarm or remote start system interfering with OEM wiring

Step-by-Step Diagnostic for B1555 #

Proper diagnosis of the B1555 code requires a systematic approach. Rushing can lead to misdiagnosis, so take your time and use the right tools (a digital multimeter and a scan tool capable of reading OEM body codes are essential). Here’s a recommended diagnostic path:

• Verify the code with a scan tool and check for related codes (especially BCM or security system codes).
• Consult wiring diagrams for the ignition run/start circuit specific to your vehicle OEM.
• Inspect the condition and operation of the ignition switch. Check for smooth action and positive engagement in all key positions.
• Test for battery voltage at the ignition switch output terminals in RUN and START positions.
• Check the integrity of wiring and connectors from the ignition switch to the BCM and related fuses/relays.
• Inspect and test all relevant fuses and relays for correct operation.
• If equipped, temporarily disconnect aftermarket alarm or remote start systems and retest.
• If all wiring and switch checks pass, follow OEM procedures to test the BCM or immobilizer module.

Possible Repairs for B1555 #

Once the cause of the B1555 code is identified, targeted repairs can restore normal function. Always use OEM-approved parts and follow recommended procedures:

• Replace a worn or defective ignition switch.
• Repair or replace damaged wiring or connectors in the ignition run/start circuit.
• Replace blown fuses and faulty relays (after confirming the underlying cause).
• Remove or professionally rewire aftermarket alarm/remote start systems interfering with OEM circuits.
• Replace the BCM or immobilizer module if conclusively proven faulty (rare).

Is It Safe to Drive with B1555? #

No. In most cases, you should not drive with a B1555 code present. This fault may leave your vehicle unable to start, or it may abruptly cut power to critical systems while driving—posing a safety risk. If the car starts and runs, the issue could still cause unpredictable electrical failures. Have the car diagnosed and repaired before regular driving resumes.

Vehicles Most Affected by B1555 #

While B1555 is a generic OBD-II code, it is most commonly reported in certain makes and models, especially those using electronic ignition switches and BCMs. The following manufacturers and vehicles have shown higher incidence, but the code can appear in many modern cars:

• Ford (F-150, Focus, Explorer, Escape)
• General Motors (Chevrolet Silverado, Malibu, GMC Sierra, Cadillac CTS)
• Chrysler/Dodge/Jeep (Ram, Grand Cherokee, Town & Country)
• Toyota (Camry, Corolla, Tacoma)
• Nissan (Altima, Sentra, Pathfinder)

Common Mistakes and Best Practices for B1555 #

It’s easy to jump to conclusions with ignition-related codes, but mistakes can be costly. Here are some pitfalls to avoid, along with tips to ensure an accurate, lasting fix:

• Replacing the ignition switch without confirming circuit voltage or physical wear
• Overlooking corroded or loose connectors (especially in humid climates)
• Ignoring the possibility of aftermarket systems causing interference
• Forgetting to check related fuses and relays
• Not clearing the code and retesting after repairs
• Always use high-quality connectors, matched gauge wire, and proper crimping/soldering techniques

Quick FAQ for B1555 #

Need a fast answer? Here are the most common questions about B1555:

• Q: Can a weak battery trigger B1555?
  A: It’s unlikely. While a dead battery may prevent starting, B1555 is specifically about the ignition run/start circuit. However, low voltage can sometimes cause related codes—test the battery as part of your diagnosis.
• Q: Do I have to reprogram anything after fixing B1555?
  A: Only if the BCM or immobilizer module is replaced. For most switch or wiring repairs, clearing the code and confirming operation is sufficient.