B1315 — Battery Saver Relay Coil Circuit Short To Battery
B1315 — Battery Saver Relay Coil Circuit Short To Battery. A fault in the ignition system. Short, gentle driving to a shop is usually possible. Typical causes: faulty ignition control circuit in the ECM, worn spark plugs or wrong plug gap, damaged coil wiring or connector.
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 B1315 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 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 B1315 does not return.
Approximate repair cost
Repair cost depends on which component actually failed. Typical scenarios for B1315 (parts and labor, USD, independent shop rates): Repair coil wiring or connector: $80–$250; Replace spark plugs: $90–$250; Replace an ignition coil: $150–$380. Overall, fixing B1315 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
Will B1315 clear itself?
Sometimes B1315 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.
How do I diagnose B1315 myself?
Start with a scan: confirm B1315, 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.
How much does it cost to fix B1315?
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 are the symptoms of B1315?
Drivers most often notice: loss of power and jerking, Check Engine Light on, increased fuel consumption, misfires under load or at idle.
What does OBD2 code B1315 mean?
B1315 — Battery Saver Relay Coil Circuit Short To Battery. A fault in the ignition system. Short, gentle driving to a shop is usually possible. Typical causes: faulty ignition control circuit in the ECM, worn spark plugs or wrong plug gap, damaged coil wiring or connector.
When your OBD2 scanner displays B1315, the vehicle's control module has identified a fault within the ignition system that falls outside acceptable operating parameters. The technical definition reads "Battery Saver Relay Coil Circuit Short To Battery," and this code lives in the body electrical category of diagnostic trouble codes. What this means in practical terms is that the module has detected a voltage condition in the ignition circuit that should not be present — either a short to battery power or a signal that violates the system's design specifications.
To set B1315, the powertrain control module monitors ignition-related sensors and circuits over multiple drive cycles, comparing real-time data against factory-calibrated thresholds. When those readings stray too far from expected values, the module logs the fault and captures a freeze frame snapshot — a precise record of engine RPM, load, coolant temperature, and vehicle speed the instant the problem occurred. That snapshot is your most valuable diagnostic clue because it tells you exactly what conditions triggered the code.
Common symptoms of B1315
B1315 typically announces itself through drivability problems that worsen under specific conditions:
- Noticeable loss of engine power and irregular acceleration or jerking
- Check Engine Light illuminated on the dashboard
- Fuel consumption noticeably higher than normal
- Misfires that occur either at idle or under engine load
- Difficulty starting the engine, particularly in damp or wet conditions
- In severe cases, a flashing Check Engine Light indicating an active misfire
What causes B1315?
Several conditions can trigger B1315, ranging from simple maintenance issues to electrical failures:
- Worn or improperly gapped spark plugs that no longer fire consistently
- Damaged or corroded wiring and connectors in the ignition coil circuit
- A failed ignition coil or coil pack unable to generate proper spark
- A faulty ignition control circuit within the engine control module
- Moisture or oil contamination present in the spark plug wells
- Chafed wiring harness insulation exposing bare wire to short circuits
- Poor electrical connections at the coil or PCM harness
How to diagnose B1315
Follow this systematic approach to isolate the root cause of B1315 without replacing parts unnecessarily:
- Connect an OBD2 scanner, retrieve B1315, and record all freeze frame data. This information reveals engine conditions when the fault first appeared and guides your inspection priorities.
- Check for related diagnostic trouble codes. Codes in the B0xxx series or ignition-related P0300-P0304 codes often point directly to the failing component. Review any technical service bulletins (TSB) for your specific make and model — manufacturers publish known fixes and software updates for recurring code patterns.
- Perform a thorough visual inspection of the ignition system wiring harness and connectors. Look for damaged insulation, corrosion at electrical contacts, chafing from contact with engine components, and any signs of moisture intrusion.
- Conduct a cylinder-to-cylinder ignition coil swap. Move the suspected coil to a different cylinder and clear the code. If B1315 moves with the coil to the new cylinder, the coil itself is faulty.
- Remove and inspect the spark plugs. Check for worn electrodes, oil fouling, carbon tracking on the ceramic insulator, and verify the gap matches factory specifications.
- Clear B1315 after your inspection and repairs, then drive the vehicle through a complete drive cycle that replicates the conditions captured in the freeze frame data. Confirm the code does not return before considering the repair complete.
How to fix B1315
Address the most likely and least expensive causes before committing to expensive component replacements. The following repairs resolve the majority of B1315 failures:
- Repair damaged coil wiring or connector: $80–$250
- Replace spark plugs: $90–$250
- Replace a faulty ignition coil: $150–$380
How much does it cost to fix B1315?
Actual repair costs depend entirely on which component triggered B1315. Here is the typical cost breakdown for parts and labor at an independent repair shop in USD:
- Wiring or connector repair: $80–$250
- Spark plug replacement: $90–$250
- Ignition coil replacement: $150–$380
Overall, addressing B1315 typically falls between $80 and $380 depending on the underlying cause. An accurate diagnosis before purchasing parts is essential — the most expensive repair is rarely the first one to investigate. Many B1315 failures trace back to worn spark plugs or simple wiring issues that cost far less than replacing the ignition coil.
Can you drive with B1315?
Drive with caution if B1315 is active. Ignition misfires allow unburned fuel to enter the exhaust system, where the catalytic converter works overtime to process it. This excess workload quickly overheats and destroys the catalytic converter — an expensive emission component. If the Check Engine Light begins flashing, stop driving immediately and have the vehicle towed to a repair facility. Continued operation with an active misfire risks permanent damage to the exhaust system and may leave you stranded.