B1357

What Does Code B1357 Mean?

Diagnostic Trouble Code (DTC) B1357, identified as “Ignition Run Circuit Short To Battery,” indicates that the Powertrain Control Module (PCM), or in some vehicle architectures, a specific body control module (BCM) or instrument cluster, has detected an anomalous electrical condition within the ignition “RUN” circuit. This critical circuit is responsible for supplying electrical power to various essential systems and components only when the ignition key is in the “RUN” position. These components typically include the fuel pump relay, engine control sensors, instrument cluster, certain relays, and other modules that require power for vehicle operation but should power down with the key off.

A “short to battery” condition signifies that the PCM has detected a voltage level on this specific ignition run circuit that is continuously at or near full battery voltage (B+) when it should not be, or when the measured voltage significantly deviates from the expected switched voltage during activation. This typically implies an unintended direct electrical connection between the ignition run circuit and a constant 12-volt battery positive supply, bypassing the intended switching mechanism of the ignition switch or associated relays. The PCM interprets this constant, unswitched voltage as an electrical fault that could lead to unintended component operation, parasitic battery drain, or a failure to power down correctly.

Common Symptoms

• Parasitic Battery Drain: The most common symptom, as components powered by the “shorted” circuit may remain active even when the vehicle is off, leading to a dead battery.
• No-Start or Intermittent Start Condition: If the short prevents proper power down cycling or interferes with critical module initialization.
• Engine Cranks, But Does Not Start: Key modules or the fuel pump may not receive proper, clean power or may be stuck in an erroneous state.
• Uncommanded Operation of Electrical Components: Certain components, such as the radio, blower motor, or instrument cluster lights, may remain on or activate intermittently even with the ignition off.
• Security System Light Illuminated: A constant or flashing security light can indicate an issue with the ignition system or related modules.
• Inoperative or Intermittent Electrical Accessories: While the short is to battery, it can disrupt the intended voltage regulation or signaling, affecting other accessories on the circuit.
• Fuses Blowing: Less common with a short to battery unless the short causes an overcurrent condition elsewhere in the circuit.

What Causes the Code B1357?

• Damaged or Chafed Wiring Harness: A section of the ignition run circuit wiring that has rubbed through its insulation and is making direct contact with a constant 12-volt battery feed wire (e.g., in the main harness, under the dash, or in the engine bay).
• Faulty Ignition Switch: An internal short or defect within the ignition switch itself, causing the “RUN” output terminal to remain energized or connected to constant battery voltage even when the key is off or in an unintended position.
• Corroded or Damaged Electrical Connectors: Water intrusion or corrosion can create unintended electrical bridges between pins within a connector, specifically between an ignition run circuit pin and a constant battery voltage pin.
• Faulty Ignition Relay or Related Relay: An internal failure within an ignition-related relay (e.g., a power distribution relay) causing its contacts to stick closed or an internal short that bypasses the coil control circuit, leading to a continuous power supply.
• Improperly Installed Aftermarket Accessories: Poorly wired aftermarket components (e.g., remote start systems, car alarms, stereo systems) that incorrectly tap into or cross-connect with the ignition run circuit and a constant battery supply.
• Internal Module Short Circuit: Less common, but an internal short within a module (e.g., PCM, BCM, Instrument Cluster) that receives power from the ignition run circuit could back-feed constant battery voltage onto the circuit.

How to Diagnose and Troubleshoot

Diagnosing B1357 requires a methodical approach, utilizing a digital multimeter (DMM), an OBD-II scanner, and vehicle-specific wiring diagrams.

1. Verify the Code and Check for Other DTCs: Use an OBD-II scanner to confirm B1357. Check for any other related codes (e.g., U-codes indicating communication issues, other B-codes related to electrical faults) and record freeze frame data. Clear the code and attempt to reproduce the fault.
2. Visual Inspection of Wiring and Connectors:
   • Disconnect the battery.
   • Carefully inspect all visible wiring harnesses related to the ignition switch, fuse box, engine bay, and under the dashboard. Look for signs of chafing, pinching, melting, or corrosion, especially where harnesses pass through firewalls or near sharp edges.
   • Inspect all connectors in the ignition circuit path. Look for bent or pushed-out pins, corrosion, water intrusion, or signs of overheating. Disconnect and re-connect relevant connectors to check for proper seating.
   • Pay close attention to any aftermarket wiring installations.
3. Ignition Switch Test:
   • With the battery reconnected (or using a suitable power probe with caution), access the ignition switch connector.
   • Using a DMM, back-probe the ignition switch output terminal(s) for the “RUN” circuit (consult wiring diagrams for specific pinouts).
   • With the key in the “OFF” position, verify that there is 0 volts on the “RUN” circuit output. If battery voltage (B+) is present, the ignition switch is highly suspect and potentially faulty internally.
   • Cycle the key through ACC, RUN, and START positions, verifying correct voltage outputs according to the wiring diagram.
4. Circuit Continuity and Short to B+ Test:
   • Disconnect the battery again.
   • Isolate the suspected “Ignition Run” circuit. This may involve disconnecting connectors downstream from the ignition switch or relays.
   • Using the DMM in continuity mode or resistance mode, check for continuity between the “Ignition Run” circuit wire and a known constant 12-volt battery wire (ensure the battery is disconnected for this test). A low resistance reading or continuity indicates a short.
   • Also, check for continuity between the “Ignition Run” circuit wire and chassis ground. While “short to battery” is the specific code, sometimes a short to ground can cause unexpected voltage drops or component behavior that might indirectly trigger related issues.
5. Relay Testing:
   • Identify and test any relays associated with the ignition run circuit (e.g., ignition relay, main power relay).
   • Remove the relay and inspect its terminals for corrosion.
   • Bench test the relay using a 12V power supply and DMM to verify proper operation of the coil and contact switching (open when de-energized, closed when energized). Pay attention to any internal resistance or signs of sticking.
6. Isolate Components: If the short is difficult to pinpoint, systematically disconnect modules or components powered by the ignition run circuit (one at a time, if possible, starting with those most easily accessible) and re-check the circuit for the short. When the short disappears, the last disconnected component or its wiring is likely the culprit.

Recommended Repairs and Solutions

The repair for B1357 is highly dependent on accurately identifying the root cause through diligent diagnosis.

1. Repair or Replace Damaged Wiring Harness: If chafed or shorted wiring is found, the damaged section must be professionally repaired. This involves cutting out the damaged segment, soldering in a new section of wire of the correct gauge, and properly insulating the repair with heat-shrink tubing and electrical tape. Ensure the repaired harness is routed and secured to prevent future damage. For extensive damage, replacing the entire harness section may be necessary.
2. Replace Faulty Ignition Switch: If diagnostic tests confirm an internal fault within the ignition switch, it must be replaced with an OEM or equivalent quality aftermarket unit. Always disconnect the battery before servicing the ignition switch.
3. Replace Faulty Relay: If an ignition-related relay is found to be stuck or internally shorted, replace it with a new, high-quality relay matching the original specifications.
4. Clean or Replace Corroded Connectors: If corrosion is present, attempt to carefully clean the connector terminals using electrical contact cleaner and a small brush. If pins are severely corroded, bent, or if the plastic housing is compromised, the connector body and/or terminals should be replaced. Ensure dielectric grease is applied to prevent future corrosion.
5. Address Aftermarket Wiring Issues: If aftermarket accessories are found to be improperly wired, they must be disconnected, and the original vehicle wiring restored to factory specifications. Any re-installation should be done by a qualified technician following proper electrical best practices, using appropriate fuses and relays.
6. Replace Faulty Module (If Applicable): In rare cases where a module is definitively diagnosed as internally shorted and causing the code, it will need to be replaced. This often requires programming or coding the new module to the vehicle’s specific VIN, which typically requires specialized diagnostic tools.

Mechanics’ Tips:

• Always disconnect the vehicle’s battery before performing any electrical repairs to prevent accidental shorts or damage to sensitive electronic components.
• Refer to the vehicle-specific factory service manual for precise wiring diagrams, connector pinouts, component locations, and voltage specifications. This is invaluable for accurate diagnosis.
• When checking for shorts, use a reliable DMM and ensure proper technique. Checking for a “short to battery” often involves disconnecting the battery and checking continuity to a known constant B+ source, or carefully checking for voltage on a circuit that should be at 0V with the key off.
• After any repair, clear the DTCs with an OBD-II scanner and perform multiple drive cycles under varying conditions to confirm the repair and ensure the code does not return.
• Be meticulous with visual inspections. Many electrical issues are found through careful examination of wiring and connectors.