B1357 — Ignition Run Circuit Short To Battery

What does OBD2 code B1357 mean?

OBD2 code B1357 flags a problem with the ignition system (ignition run circuit short to battery). Short, gentle driving to a shop is usually possible. Common culprits: failed ignition coil or coil pack, moisture or oil in the spark plug wells, faulty ignition control circuit in the ECM.

How much does it cost to fix B1357?

Repair coil wiring or connector — $80–$250; Replace spark plugs — $90–$250; Replace an ignition coil — $150–$380. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What is the most common cause of B1357?

The most common causes are: failed ignition coil or coil pack, moisture or oil in the spark plug wells, faulty ignition control circuit in the ECM.

How do I diagnose B1357 myself?

Start with a scan: confirm B1357, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the ignition system, and verify the suspect component against live data before buying parts.

What are the symptoms of B1357?

Drivers most often notice: loss of power and jerking, increased fuel consumption, misfires under load or at idle, Check Engine Light on.

The engine control module (ECM) monitors the ignition circuit continuously while the engine is running. When it detects voltage on the ignition run circuit when that circuit should be switched off — essentially a battery feed that doesn't belong there — it sets trouble code B1357: Ignition Run Circuit Short to Battery. This code falls within the body electrical category of OBD2 diagnostics, which means it relates to the vehicle's electrical infrastructure rather than engine sensor readings directly.

To trigger B1357, the ECM compares real-time voltage readings against factory-defined parameters, typically over multiple drive cycles before confirming a fault. The module also saves a freeze frame snapshot alongside the code — a record of engine RPM, load percentage, coolant temperature, and vehicle speed at the exact moment the problem occurred. Reviewing that snapshot first narrows down the diagnosis significantly. The ignition run circuit itself works simply: battery voltage feeds the coil when the ignition key is in the run position, and the ECM controls when the coil fires by grounding its driver circuit. A short in the wiring or connector can keep the coil powered when it should be off, which is exactly what B1357 flags.

Symptoms

• Check Engine Light illuminates on the dashboard
• Engine runs rough, stumbles, or lacks power under acceleration
• Misfires noticeable at idle or under load
• Fuel economy drops noticeably compared to normal
• Hard starting, especially in damp or rainy conditions
• In severe cases, the engine may stall completely

Causes

• Failed ignition coil or coil pack — the most frequent culprit when B1357 appears
• Damaged or corroded wiring harness and connectors feeding the ignition circuit
• Moisture or oil contamination inside the spark plug wells
• Worn spark plugs or plugs with incorrect gap spacing
• Faulty ignition control circuit inside the ECM itself (less common)
• Poor electrical connections at the coil or related connectors

How to Diagnose

1. Plug in an OBD2 scanner and verify B1357 is stored in the ECM memory. Save the freeze frame data — it tells you exactly what the engine was doing when the fault set, which guides your inspection.
2. Note any other diagnostic trouble codes present. Related codes often point to the underlying cause. Also check for manufacturer technical service bulletins (TSBs) specific to your vehicle — some B0xxx codes have known factory remedies or updated software calibrations.
3. Perform a hands-on inspection of the wiring and connectors going to the ignition coil. Look for frayed insulation, broken wires, corrosion on the terminals, loose plugs, or any sign of water intrusion.
4. Try swapping the ignition coil to a different cylinder. If the fault code migrates to that cylinder's position, the coil is faulty. If it stays put, the problem lies in the wiring or connector for that circuit.
5. Remove and inspect the spark plugs. Check for worn electrodes, oil deposits, carbon tracking on the ceramic, and verify that the gap matches factory specifications.
6. Clear the code and complete a full drive cycle that reproduces the conditions from the freeze frame. If B1357 returns, the fault is still present and active.

Repair Options

Depending on which component triggered the code:

• Repair or replace damaged wiring and connectors in the ignition circuit — parts and labor typically run $80–$250 at an independent shop
• Replace worn or damaged spark plugs — expect to pay $90–$250 for parts and installation
• Replace a faulty ignition coil or coil pack — this is the most common fix, with parts and labor ranging from $150–$380

Total Cost to Fix B1357

The exact repair cost depends entirely on which part is actually faulty. Based on typical independent shop labor rates, here is what most drivers end up paying:

• Wiring or connector repair: $80–$250
• Spark plug replacement: $90–$250
• Ignition coil replacement: $150–$380

Most repairs for B1357 fall somewhere between $80 and $380 total. A methodical diagnosis before buying parts is worth the time — the most expensive component is rarely the first one to check.

Can You Drive With B1357?

Drive with caution and avoid heavy loads or hard acceleration. Ignition faults that cause misfires can dump unburned fuel into the exhaust, overheating and destroying the catalytic converter over time. If the Check Engine Light is flashing, stop driving immediately and address the problem before it worsens. The engine may run poorly or stall without warning, leaving you stranded. Keep speeds moderate and prioritize getting the vehicle diagnosed within the next day or two — the underlying issue is usually simple and inexpensive to repair.