B1356 — Ignition Run Circuit Open

OBD2 code B1356 flags a problem with the ignition system (ignition run circuit open). Short, gentle driving to a shop is usually possible. Common culprits: damaged coil wiring or connector, moisture or oil in the spark plug wells, worn spark plugs or wrong plug gap.

body electrical

Is it safe to drive?

Drive with caution Drive with caution and avoid load. Ignition faults cause misfires that quickly overheat and destroy the catalytic converter; if the Check Engine Light flashes, stop and fix it first.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm B1356 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many B0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the ignition system for damage, corrosion, chafing or poor contact.
Subsystem check Do a continuity test end-to-end on the ignition run circuit and wiggle the harness while measuring — intermittent opens show up as fluctuating readings.
Subsystem check Swap the coil to another cylinder and see if the fault code follows it.
Subsystem check Inspect spark plugs for wear, oil or carbon tracks and check plug gaps.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm B1356 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1356 (parts and labor, USD, independent shop rates): Replace spark plugs: $90–$250; Replace an ignition coil: $150–$380; Repair coil wiring or connector: $80–$250. Overall, fixing B1356 usually costs between $80 and $380. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

How do I diagnose B1356 myself?

Start with a scan: confirm B1356, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the ignition run, and verify the suspect component against live data before buying parts.

What are the symptoms of B1356?

Drivers most often notice: increased fuel consumption, misfires under load or at idle, Check Engine Light on, hard starting, especially in damp weather.

How much does it cost to fix B1356?

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

Is it safe to drive with B1356?

Drive with caution and avoid load. Ignition faults cause misfires that quickly overheat and destroy the catalytic converter; if the Check Engine Light flashes, stop and fix it first.

What does OBD2 code B1356 mean?

When your scan tool pulls code B1356, it means the engine computer has detected that the ignition run circuit is not completing its electrical path as expected. The technical label is "Ignition Run Circuit Open," and it falls under the body control or chassis electrical category depending on your vehicle's architecture.

The ignition run circuit carries voltage to the ignition coils and spark plugs once the engine is running. "Circuit open" describes a break in that path — current cannot flow where the module expects it. This happens when a wire has fractured, a connector is unplugged or corroded, a fuse has blown, or an internal component has failed. The PCM monitors this circuit continuously and stores B1356 only after confirming the fault under specific operating conditions. The freeze frame data saved alongside B1356 reveals engine load, RPM, coolant temperature, and vehicle speed at the moment the fault occurred, giving you the exact conditions to reproduce during testing.

Symptoms of B1356

Check Engine Light illuminates
Engine misfires during acceleration or at idle
Fuel economy drops noticeably
Hard starting, especially in damp or rainy conditions
Reduced power output and hesitation under load
Rough idle or engine stalling

What causes B1356?

Loose, corroded, or backed-out electrical connector in the ignition circuit
Broken or chafed wiring within the ignition run harness
Blown fuse supplying the ignition run circuit
Worn, fouled, or incorrectly gapped spark plugs
Failed ignition coil or coil pack
Damaged coil wiring harness or connector terminal
Faulty ignition control circuit inside the ECM or PCM
Internally open ignition run relay or feed

How to diagnose B1356

Connect an OBD2 scanner and confirm B1356 is stored in the PCM memory. Save the freeze frame data — it shows engine load, RPM, coolant temperature, and speed when the fault was detected. Replicate those exact conditions during your diagnosis.
Look for any related diagnostic trouble codes. Codes in the same family often point to the root cause. Also search for manufacturer TSBs (Technical Service Bulletins) for your specific make, model, and year — many B1356-related issues have known factory fixes or PCM software updates available through the manufacturer website or NHTSA database.
Perform a thorough visual inspection of the ignition circuit wiring and connectors. Look for damaged insulation, corroded pins, broken wires, or loose plugs. Pay special attention to areas where the harness bends or passes near heat sources.
Test the ignition run circuit for continuity end-to-end using a multimeter. Gently wiggle the harness while monitoring the reading — an intermittent open will cause the multimeter display to fluctuate or go OL (open loop).
Swap the ignition coil with a known-good unit from another cylinder and clear the code. If B1356 moves to the cylinder where you installed the suspect coil, the coil itself is faulty. If the code stays, the problem lies elsewhere in the wiring or PCM.
Remove and inspect the spark plugs for wear, carbon buildup, oil fouling, or incorrect electrode gap. Replace if necessary.
Clear the code, complete a full drive cycle including the conditions recorded in the freeze frame, and verify that B1356 does not return. If it comes back, the underlying fault is still present.

Repair options and costs

Replace worn or fouled spark plugs: $90–$250
Replace a faulty ignition coil or coil pack: $150–$380
Repair damaged coil wiring or corroded connector terminals: $80–$250

How much does fixing B1356 cost?

The total bill depends entirely on which part is actually at fault. If worn spark plugs are the culprit, expect to pay between $90 and $250 for parts and labor at an independent shop. If the ignition coil has failed, the cost climbs to $150–$380. Wiring or connector repairs typically run $80–$250 depending on the extent of the damage. Labor charges at most independent shops add roughly $50–$100 on top of parts costs. The key to keeping costs down is accurate diagnosis before you buy parts — the most expensive scenario is rarely where you should start.

Can you drive with B1356?

Drive with caution. B1356 is classified as a caution-level fault. When the ignition circuit fails intermittently, the resulting misfires send unburned fuel into the exhaust system, which can overheat and destroy the catalytic converter — an extremely expensive repair. If the Check Engine Light is solid, you can drive a short distance to a shop, but have it diagnosed promptly. If the light is flashing, stop driving immediately and arrange a tow. Continued operation will worsen fuel economy, reduce power, and risk damage to emissions components.