P1340 — Misfire Rate Catalyst Damage Fault - Bank 2

What does OBD2 code P1340 mean?

OBD2 code P1340 flags a problem with the engine misfire monitoring (misfire rate catalyst damage fault - bank 2). Short, gentle driving to a shop is usually possible. Common culprits: incorrect fuel pressure or a weak fuel pump, faulty crankshaft/camshaft position signal, failed ignition coil or coil wiring.

Will P1340 clear itself?

Sometimes P1340 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 P1340?

Drivers most often notice: unusual exhaust smell, rough idle and engine shaking, loss of power during acceleration, increased fuel consumption.

Is it safe to drive with P1340?

Drive only as much as necessary. An active misfire sends unburned fuel into the exhaust and can destroy the catalytic converter within hours, especially if the Check Engine Light is flashing — in that case stop driving and diagnose immediately.

How much does it cost to fix P1340?

Clean or replace a fuel injector — $200–$600; Replace spark plugs — $90–$250; Replace an ignition coil — $150–$380; 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.

Seeing P1340 pop up on your OBD2 scanner is your engine's way of telling you something is wrong with the way it fires cylinders on the rear bank. The control unit — your car's powertrain module — monitors every misfire that occurs and logs a fault when the misfire rate exceeds a threshold that could actually damage downstream components. P1340 translates to "Misfire Rate Catalyst Damage Fault – Bank 2," which means the problem is serious enough that raw, unburned fuel could be heading straight for your catalytic converter. This is a powertrain-level code, meaning it touches both the engine and the emissions hardware the engine feeds into.

"Bank 2" refers to the engine bank that does not contain cylinder number one. On V-shaped engines this is the passenger-side bank, while on inline engines with two catalytic converters it typically refers to the exhaust side opposite cylinder one. Knowing your specific engine layout matters here — misdiagnosing which bank is affected leads to replacing good parts while the real culprit stays broken. The ECU sets P1340 by comparing live misfire sensor data against factory-calibrated thresholds, usually over multiple drive cycles, and it captures a freeze frame snapshot at the moment the threshold is breached. That snapshot records RPM, engine load, coolant temperature, and vehicle speed, and it is the single most useful starting point for any meaningful diagnosis.

Common Symptoms of P1340

The symptoms you notice depend on how severe the underlying misfire has become, but several patterns show up repeatedly with this code.

• A noticeable sulfur or raw-fuel smell coming from the exhaust, especially when the engine is warm
• Rough idle that makes the whole vehicle shake or vibrate at a standstill
• Hesitation or stumble when you press the accelerator, particularly under heavier loads
• A measurable drop in fuel economy compared to what you normally see
• Reduced engine power — the car feels sluggish and unresponsive when you need to accelerate
• An illuminated Check Engine Light, and on some vehicles a flashing CEL indicating an active, continuous misfire

What Causes P1340?

The root causes of P1340 are broadly similar to any misfire code, though they must be evaluated in the context of Bank 2 specifically. The most frequently seen culprits, listed from most to least common.

• An intake vacuum leak allowing unmetered air into the cylinders on the affected bank
• Spark plugs that are worn out, fouled with carbon deposits, or have improper gaps
• Low cylinder compression from worn rings, failed head gaskets, or burnt valves on one or more cylinders in Bank 2
• A faulty crankshaft or camshaft position sensor disrupting the precise timing signals the ECU needs to fire injectors and ignition coils at the correct moment
• Fuel injector failure or severe clogging on the affected cylinders
• An ignition coil or coil pack failure on Bank 2 cylinders
• Wiring or connector problems in the engine's sensor and ignition circuits related to the rear bank

How to Diagnose P1340

Working through this code systematically pays off. Skipping steps leads to replacing parts that were not actually broken.

1. Pull the code and record the freeze frame. Connect your scanner, confirm P1340 is stored, and save every piece of data the ECU captured — RPM, load, coolant temp, and vehicle speed at the moment of failure. These conditions are your target when testing and verifying the repair.
2. Scan for related codes and check TSBs. Secondary codes often point directly to the failing component. Also look up any factory technical service bulletins for your make, model, and year — manufacturers publish software updates and known-fix campaigns that a scanner will not show you.
3. Inspect wiring and connectors. Check the harness and connectors tied to the crankshaft position sensor, camshaft position sensor, and ignition components on Bank 2. Look for chafed insulation, corrosion at the pins, or connectors that are not fully seated.
4. Read per-cylinder misfire counters in live data. This narrows the fault to one or two specific cylinders, which tells you exactly where to focus your testing.
5. Perform a cylinder swap test. Move the ignition coil or fuel injector from the suspected cylinder to a known-good cylinder and see if the misfire follows the part. If it does, that part is the problem.
6. Clear the code and run a complete drive cycle. Replicate the conditions recorded in the freeze frame — same RPM, load, and temperature range — to confirm the fault does not return before calling the job done.

Repair Options and Cost to Fix P1340

Once you have pinpointed the failing component, repair costs fall into a clear range. All prices below reflect parts and labor at independent shop rates in the United States.

• Clean or replace a clogged or failed fuel injector: $200 – $600
• Replace worn or fouled spark plugs: $90 – $250
• Replace a faulty ignition coil on Bank 2: $150 – $380
• Address low compression with engine mechanical repair: $800 – $2,500

These are standalone component costs. If your diagnosis reveals more than one failed part — for example, bad plugs AND a failing coil — add the figures accordingly. On the low end, a simple spark plug replacement on the correct cylinders often clears P1340 entirely. On the high end, compression-related failures that require disassembly are a significant investment, which is exactly why a methodical diagnosis before buying parts makes financial sense.

Can You Drive with P1340?

Use caution. An active misfire on Bank 2 allows unburned fuel to pass into the exhaust stream, and that raw fuel heats up the catalytic converter in ways it was not designed to handle. If the catalytic converter fails, you are looking at a repair that dwarfs the cost of fixing the original misfire. More critically, if your Check Engine Light is flashing rather than solidly illuminated, the misfire is continuous and severe — in that situation you should stop driving immediately and have the vehicle towed to a shop. Even with a steady CEL, limit your driving to getting the car to a diagnostic facility and avoid heavy loads or high RPMs until the problem is resolved.

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