P1385 — Misfire Detected - Rough Road Data Not Available

What does OBD2 code P1385 mean?

P1385 — Misfire Detected - Rough Road Data Not Available. A fault in the engine misfire monitoring. Short, gentle driving to a shop is usually possible. Typical causes: vacuum leak in the intake, clogged or leaking fuel injector, incorrect fuel pressure or a weak fuel pump.

How do I diagnose P1385 myself?

Start with a scan: confirm P1385, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the engine misfire monitoring, and verify the suspect component against live data before buying parts.

How much does it cost to fix P1385?

Replace an ignition coil — $150–$380; Replace spark plugs — $90–$250; Clean or replace a fuel injector — $200–$600; Engine mechanical repair (compression) — $800–$2,500. 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 P1385?

Drivers most often notice: unusual exhaust smell, loss of power during acceleration, rough idle and engine shaking, Check Engine Light on or flashing.

Will P1385 clear itself?

Sometimes P1385 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.

When the engine control module (ECM) stores OBD2 code P1385, it is reporting a specific fault: the PCM detected a misfire but could not evaluate the condition against rough-road data because that data was unavailable. In other words, the system knows something is wrong with combustion, but it lacks the road-surface context needed to rule out benign vibrations from potholes or uneven pavement. The powertrain control module sets P1385 after comparing live engine-misfire monitoring readings against its factory calibration thresholds, typically over multiple drive cycles. As with all stored codes, the ECM also captures a freeze-frame snapshot — engine speed, load, coolant temperature, and vehicle speed at the exact moment the fault was recorded. That snapshot is the first thing a technician pulls because it tells you exactly what conditions triggered the code, which narrows the investigation significantly.

P1385 belongs to the powertrain family of OBD2 codes and is most commonly found on vehicles equipped with advanced misfire detection algorithms that factor in road-surface input from the anti-lock brake system or wheel-speed sensors. When those signals are missing, corrupted, or otherwise unavailable, the PCM flags rough-road data as not available and sets the code alongside whatever misfire it has already identified. This means P1385 is not a standalone electrical failure — it is a monitoring-system limitation that compounds an underlying misfire condition. The root cause can be as simple as bad spark plugs or as serious as internal engine damage, but the missing rough-road data must be understood before you can properly interpret the severity of the misfire itself.

The most obvious clue is the Check Engine Light — either steady or flashing. A flashing CEL while driving is a direct signal to pull over and stop because an active misfire is pushing raw fuel through the exhaust, which can overheat and destroy a catalytic converter in a short time. Beyond the light, drivers typically notice rough idle or a shaking sensation at stoplights, a jerky or hesitant response when pressing the accelerator, a noticeable drop in engine power during acceleration, and an unusual smell from the exhaust — often described as sulfur or raw gasoline. Fuel economy also suffers noticeably when one or more cylinders are misfiring, since unburned fuel is wasted with every engine cycle.

Common Symptoms of P1385

• Check Engine Light illuminated or flashing
• Rough idle and visible engine shaking
• Loss of power during acceleration
• Jerking or hesitation when under load
• Unusual exhaust odor (raw fuel or sulfur)
• Noticeably increased fuel consumption

The causes behind P1385 generally trace back to whatever is disrupting normal combustion in one or more cylinders. Worn or fouled spark plugs are the single most frequent culprit — they lose their ability to create a strong, consistent spark, especially under load. Faulty crankshaft or camshaft position sensor signals also trigger the code because the PCM relies on precise timing data to detect misfires accurately; if the signal is noisy or missing, the controller cannot properly correlate cylinder events. A vacuum leak in the intake manifold introduces unmetered air that throws off the air-fuel mixture, leading to incomplete combustion and misfire detection. Failed ignition coils, damaged coil wiring, or failing fuel injectors round out the most common causes, with each capable of producing the exact pattern the ECM is watching for.

What Causes P1385

• Worn or fouled spark plugs
• Faulty crankshaft or camshaft position sensor signal
• Vacuum leak in the intake manifold
• Failed ignition coil or damaged coil wiring
• Failing or clogged fuel injector

How to Diagnose P1385

1. Connect an OBD2 scanner and confirm that P1385 is stored. Save the freeze-frame data immediately — it shows rpm, load, coolant temperature, and vehicle speed at the moment of failure, which tells you exactly what driving conditions triggered the code.
2. Look for any related diagnostic trouble codes stored alongside P1385. Codes for crankshaft position, camshaft position, fuel injector, or ignition coil faults often point directly to the root cause. Also check manufacturer TSBs for your specific make and model — the NHTSA database and the manufacturer's own site allow VIN-based searches, and many P0xxx codes have documented factory fixes or software updates.
3. Visually inspect the wiring harness and all connectors related to the misfire monitoring system, including crankshaft and camshaft position sensors, ignition coils, and fuel injectors. Look for chafed insulation, corrosion, broken wires, or loose terminals.
4. Pull up per-cylinder misfire counters in the scanner's live data screen. This tells you which cylinder or cylinders are misfiring and how severe the count is for each one.
5. Perform a cylinder swap test: exchange an ignition coil or fuel injector from a misfiring cylinder with one from a healthy cylinder, clear the code, and run the vehicle again. If the misfire moves to the new cylinder, the part you swapped is defective.
6. Clear the code and complete a full drive cycle that reproduces the conditions captured in the freeze frame. If P1385 does not return, the issue may have been intermittent. If it returns, you have confirmed an active fault that requires repair.

Repair Options and Costs for P1385

Repair always starts with the cheapest and most likely causes before moving to expensive components. Ignition coil replacement runs $150–$380 for parts and labor at an independent shop. Spark plug replacement, including labor, typically costs $90–$250. If a fuel injector is at fault, cleaning costs fall in the $200–$350 range while full replacement runs $200–$600. In cases where low compression or an internal mechanical problem is the underlying cause, engine mechanical repair can reach $800–$2,500 or more depending on what is found.

How Much Does It Cost to Fix P1385?

The total bill depends entirely on which part is actually failing. At independent shop rates, the realistic range is $90 to $2,500. Most vehicles set P1385 because of spark plugs or ignition coils — both relatively inexpensive to address. Fuel injector issues cost more, and internal engine repairs are the least common but most costly scenario. The single most important step before spending any money is confirming the root cause with a scanner and a proper inspection. Buying expensive parts on guesswork is how a $150 problem becomes a $1,500 bill.

Can You Drive with P1385?

Drive only as much as necessary to reach a safe location for diagnosis. An active misfire allows unburned fuel to enter the exhaust stream, and that fuel can ignite inside the catalytic converter, causing rapid and expensive damage. If your Check Engine Light is flashing, stop driving immediately — continued operation risks catalytic converter failure, which is both a emissions violation and a costly repair. Even if the light is steady, have the vehicle inspected at the earliest opportunity.

Related OBD2 codes

• P1300: Multi-faults - Bank 1 - With Low Side Shorts
• P1301: Multi-faults - Bank 2 - With Low Side Shorts
• P1302: Injector High Sides Shorted Together
• P1303: IDM Failure
• P1304: Cylinder Head Overtemperature Protection Active
• P1305: Boost Calibration Fault