OBD Code B1357: Ignition Run Circuit Short To Battery

Q: What does OBD code B1357 mean?

Ignition Run Circuit Short To Battery. The ignition run circuit is detecting excessive voltage, as if it's being shorted directly to the battery instead of being properly controlled. Think of it like a water line that's supposed to have controlled flow but instead has a direct pipe to the main supply, causing pressure to spike.

Q: How do I fix OBD fault code B1357?

Inspect for corrosion, bent pins, or damaged connectors in the ignition switch harness and reseat connections.. Test or replace the relay that controls the ignition run circuit for internal shorts.. Check for pinched, melted, or damaged wiring between the BCM and ignition switch; repair or replace as needed.

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What This Actually Means

In plain language — no jargon

The ignition run circuit is detecting excessive voltage, as if it's being shorted directly to the battery instead of being properly controlled. Think of it like a water line that's supposed to have controlled flow but instead has a direct pipe to the main supply, causing pressure to spike.

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Symptoms You May Notice

3 known symptoms for this code

Illuminated check engine light or body control module warning

Vehicle may not start or has erratic starting behavior

Electrical systems or accessories behaving unexpectedly

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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The body control module monitors the ignition run circuit voltage through a dedicated input pin. It expects to see a controlled voltage signal that transitions properly during ignition key cycles. When the module detects voltage at or near battery potential (12-14V) when it should be lower or switching, it logs a short-to-battery fault.

Voltage & Parameter Thresholds

Parameter	Normal Range	Fault Condition
Ignition Run Circuit Voltage	0-5V controlled signal or switched ground	9.5V+ sustained when circuit should be inactive
Circuit Resistance	Proper relay/switch operation with <1 ohm closed	Direct short path to battery (+12V rail)

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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex

1

Ignition switch or steering column connectors

Inspect for corrosion, bent pins, or damaged connectors in the ignition switch harness and reseat connections.

2

Ignition run relay

Test or replace the relay that controls the ignition run circuit for internal shorts.

3

Body control module or wiring harness

Check for pinched, melted, or damaged wiring between the BCM and ignition switch; repair or replace as needed.

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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1357 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.

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How to Clear Code B1357

What happens after you fix the fault

Once the fault is repaired, B1357 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When

Fault has been diagnosed and repaired
You want to confirm the repair worked
Code appeared after a sensor was cleaned

⚠️ Do Not Clear When

Preparing for an emissions/PUC test
Root cause is still undiagnosed
Check engine light is flashing

Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.