B1302 — Accessory Delay Relay Coil Circuit Failure

What does OBD2 code B1302 mean?

OBD2 code B1302 flags a problem with the ignition system (accessory delay relay coil circuit failure). Short, gentle driving to a shop is usually possible. Common culprits: failed ignition coil or coil pack, damaged coil wiring or connector, worn spark plugs or wrong plug gap.

What is the most common cause of B1302?

The most common causes are: failed ignition coil or coil pack, damaged coil wiring or connector, worn spark plugs or wrong plug gap.

How much does it cost to fix B1302?

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

Will B1302 clear itself?

Sometimes B1302 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.

What are the symptoms of B1302?

Drivers most often notice: increased fuel consumption, hard starting, especially in damp weather, loss of power and jerking, misfires under load or at idle.

When the powertrain module detects an abnormal condition in the accessory delay relay coil circuit, it logs OBD2 code B1302. This fault belongs to the body electrical category, meaning the problem sits in the circuitry controlling the relay rather than the engine itself. The module performs repeated checks over multiple drive cycles before confirming the fault, which is why you might notice symptoms before the Check Engine Light actually appears.

The accessory delay relay plays a supporting role in your vehicle's electrical ecosystem. When you turn the ignition off, this relay allows certain accessories—often the radio, power windows, or interior lights—to remain powered for a brief period. If the relay coil circuit fails, that delayed operation either stops working entirely or behaves erratically. The ECU stores B1302 once its internal logic determines the circuit has fallen outside acceptable parameters.

What makes B1302 particularly useful during diagnosis is the accompanying freeze frame data. Think of it as a photograph taken at the exact moment the fault occurred, capturing engine RPM, load percentage, coolant temperature, and vehicle speed. This snapshot helps you recreate the conditions that triggered the code, saving considerable time when you're chasing intermittent problems.

Symptoms of B1302

• Increased fuel consumption as the engine compensates for misfires
• Hard starting, particularly noticeable in damp or rainy conditions
• Noticeable loss of power during acceleration
• Engine jerking or stumbling under load
• Misfires occurring either at idle or under acceleration
• Check Engine Light illuminated on the dashboard

Common Causes

• Damaged wiring or connectors feeding the accessory delay relay coil circuit
• Failed ignition coil or coil pack delivering weak or inconsistent spark
• Worn spark plugs or incorrect plug gap preventing proper combustion
• Faulty ignition control circuit within the ECM or PCM itself

How to Diagnose B1302

1. Connect a quality OBD2 scanner and verify that B1302 is stored in the system. Save the freeze frame data immediately—this information reveals engine conditions when the module first detected the fault and guides your testing priorities.

2. Pull any related trouble codes before clearing anything. Codes appearing alongside B1302 often point to the root cause. Check manufacturer technical service bulletins using your VIN at the manufacturer website or NHTSA database; many body electrical faults have documented factory fixes or software updates.

3. Perform a thorough visual inspection of the wiring harness and connectors associated with the accessory delay relay and ignition system. Look for damaged insulation, corroded terminals, chafing from contact with other components, or loose-fitting connectors that could cause intermittent opens.

4. If the vehicle runs poorly, swap the ignition coil to a different cylinder and monitor whether B1302 moves with it. A code that follows the coil confirms the coil itself has failed.

5. 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. Incorrect gap causes misfires that can trigger accessory circuit faults.

6. Clear the code and complete a full drive cycle, including the specific operating conditions captured in the freeze frame. If B1302 does not return, the fault was likely intermittent. A recurring code confirms an active problem requiring repair.

Repair Options

• Repair damaged coil wiring or connectors: $80–$250
• Replace a faulty ignition coil: $150–$380
• Replace worn or damaged spark plugs: $90–$250

Total Cost to Fix B1302

Your actual expense depends entirely on which component is responsible. In most cases, the problem traces to wiring damage or a failing coil rather than the control module itself. Independent shop labor rates typically add $75–$125 per hour depending on location. An accurate diagnosis before purchasing parts prevents unnecessary spending—replacing an expensive ECM when the real issue is a $15 connector happens more often than you'd think. Budget between $80 and $380 to resolve B1302 completely.

Can You Drive with B1302?

Caution is warranted. While the vehicle may continue operating, ignition-related faults cause misfires that introduce unburned fuel into the exhaust stream. That raw fuel overheats the catalytic converter and can cause permanent damage if ignored. If the Check Engine Light begins flashing rather than steady, reduce speed immediately and arrange repairs—flashing indicates a misfire severe enough to risk catalytic converter failure. Short trips to a trusted shop are acceptable; extended highway driving under load is not recommended until the fault is resolved.

Related OBD2 Codes

• B1300: Power Door Lock Circuit Failure
• B1301: Power Door Lock Circuit Open
• B1303: Accessory Delay Relay Coil Circuit Open
• B1304: Accessory Delay Relay Coil Circuit Short To Battery
• B1305: Accessory Delay Relay Coil Circuit Short To Ground
• B1306: Oil Level Switch Circuit Open