B1355

What Does Code B1355 Mean?

DTC B1355 signifies an “Ignition Run Circuit Failure” and is typically set by the Powertrain Control Module (PCM), Engine Control Module (ECM), or in some vehicle architectures, the Body Control Module (BCM). This code indicates that the control module has detected an abnormal voltage condition (either excessively low, high, or an open circuit) on the dedicated 12-volt supply circuit that is active when the ignition key is in the “RUN” position. The “Ignition Run” circuit provides switched power to a multitude of critical components essential for vehicle operation, including the PCM/ECM itself, fuel pump relay, ignition coils, various sensors (e.g., crankshaft position, camshaft position, oxygen sensors, mass airflow), injectors, and often portions of the instrument cluster and other accessory modules. The module monitors this circuit to ensure all dependent systems receive the necessary operational voltage. When the detected voltage deviates from the specified operational window for a calibrated period, the code B1355 is stored, indicating a fundamental power supply integrity issue affecting the vehicle’s ability to operate reliably.

Common Symptoms

• No Crank/No Start Condition: The most severe symptom, as critical components may not receive power.
• Engine Stalls Intermittently or Unexpectedly: Loss of ignition run power while driving can cause immediate engine shutdown.
• Intermittent Loss of Power to Accessories: Radio, HVAC blower, dashboard lights, or other convenience items may cut out.
• Warning Lights Illuminated: Beyond the Check Engine Light (CEL), other warning lights like Battery, ABS, Airbag, or Stability Control may illuminate due due to power loss to their respective control modules.
• Difficult Starting: The engine may crank but struggle to start, or start and immediately die.
• Electrical System Glitches: Erratic behavior from various vehicle electrical systems.

What Causes the Code B1355?

• Faulty Ignition Switch: Worn or damaged internal contacts within the ignition switch fail to consistently provide proper voltage to the “RUN” circuit.
• Wiring Harness Damage: An open circuit, short to ground, short to voltage, or high resistance within the ignition run circuit wiring. This can be due to chafing, corrosion, or physical damage, often in areas like the steering column or firewall pass-throughs.
• Blown Fuse or Fusible Link: An open fuse or fusible link protecting the main ignition run circuit can interrupt power. Often, a blown fuse indicates an underlying short circuit elsewhere.
• Faulty Ignition Run Relay: If the vehicle utilizes a dedicated relay to distribute ignition run power, a defective relay (e.g., burnt contacts, open coil) will prevent power flow.
• Corroded or Loose Electrical Connections: High resistance at critical connectors along the ignition run circuit path, such as at the ignition switch, fuse box, relay, or PCM/ECM.
• Faulty Control Module (PCM/ECM/BCM): While less common, an internal failure within the control module responsible for monitoring or supplying the ignition run voltage can trigger this code.

How to Diagnose and Troubleshoot

Diagnosis of B1355 requires a methodical approach, focusing on the integrity of the 12-volt ignition run circuit using a Digital Multimeter (DMM) and an OBD-II scanner.

1. Initial Visual Inspection: Begin by checking the battery terminals for corrosion or looseness. Inspect the entire visible wiring harness for signs of physical damage, chafing, burning, or loose connectors, especially around the steering column, fuse boxes, and engine bay.
2. OBD-II Scanner & Live Data:
   • Connect an OBD-II scanner and retrieve all stored DTCs. Look for any additional codes (P, B, U codes) that may provide clues to associated electrical failures.
   • Monitor live data parameters, specifically battery voltage and, if available, ignition switch position status or various module supply voltages. Observe if the voltage drops significantly or disappears when the key is in the “RUN” position.
3. Battery Voltage Test:
   • Using a DMM, measure the battery voltage directly at the battery terminals. It should be approximately 12.6 volts for a fully charged battery. A low battery can cause a variety of electrical issues, though B1355 typically points to a circuit failure rather than overall low voltage.
4. Ignition Switch Output Test:
   • Locate the ignition switch connector (often under the steering column). With the key in the “RUN” position, use the DMM to back-probe or disconnect the connector and measure the voltage on the output wire(s) designed to carry power to the ignition run circuit. Compare this reading to the battery voltage. A significant voltage drop (more than 0.5V) indicates a faulty ignition switch.
5. Fuse Panel & Relay Testing:
   • Identify all fuses and fusible links related to the ignition switch, PCM/ECM, fuel pump, and any main ignition power distribution. With the key in the “RUN” position, use the DMM to check for voltage on both sides of each fuse. A fuse showing voltage on one side but not the other is blown. Replace the fuse and investigate the cause of the blow.
   • If an ignition run relay is present, test its operation. Verify that the relay coil receives power and ground when the key is in “RUN,” and that the contacts close, allowing battery voltage to pass through to the load side. You can often swap the relay with a known good, identical relay from a non-critical circuit for a quick test.
6. Circuit Continuity and Voltage Drop Testing:
   • With the battery disconnected, perform continuity checks (ohms) on suspect wiring segments between the ignition switch/relay and the components it powers (e.g., PCM connector). Look for open circuits (infinite resistance) or shorts to ground (0 ohms to ground).
   • Perform a voltage drop test across suspect wiring segments or connectors in the ignition run circuit while the circuit is under load (e.g., key in RUN position). Place the DMM leads across the component or wire segment; any reading greater than 0.2V indicates excessive resistance in that section.

Recommended Repairs and Solutions

Once the source of the ignition run circuit failure has been identified through systematic diagnosis, the following repairs are typically recommended:

• Replace Faulty Ignition Switch: If DMM tests confirm the ignition switch is not consistently supplying adequate voltage to the run circuit. Ensure the replacement switch is of OEM quality or equivalent.
• Repair or Replace Damaged Wiring Harness: Address any open circuits, shorts, or high-resistance sections in the ignition run wiring. Utilize appropriate automotive-grade wire, solder connections, and heat shrink tubing for durable, weather-resistant repairs. For extensive damage, harness replacement may be necessary.
• Replace Blown Fuses or Fusible Links: Always identify and rectify the underlying cause of a blown fuse (e.g., a short circuit in a component or wiring) before simply replacing it, to prevent immediate re-failure.
• Replace Faulty Ignition Run Relay: If the relay’s coil or contacts are defective, replacing it with an OEM or high-quality aftermarket equivalent will restore power distribution.
• Clean and Tighten Electrical Connections: Disconnect any corroded or loose connectors, clean the terminals using electrical contact cleaner and a brush, and apply a thin layer of dielectric grease before reassembly to prevent future corrosion and ensure a solid connection.
• PCM/ECM/BCM Replacement (Last Resort): If all wiring, fuses, relays, and the ignition switch have been thoroughly tested and confirmed to be in good working order, and internal module failure is strongly suspected, the control module may need replacement. This often requires specialized programming or flashing with the vehicle’s specific software after installation.
• Post-Repair Verification: After completing any repair, clear all stored DTCs with an OBD-II scanner. Perform several drive cycles under varying conditions to confirm the B1355 code does not return and that all systems powered by the ignition run circuit function correctly. Monitor live data for stable ignition run circuit voltage.