AutoCodes – Generic – P0312

P0312 Code - Cylinder 12 Misfire Detected

Quick Answer

The Engine Control Module (ECM) uses information from the crankshaft position sensor and the camshaft position sensor to determine when an engine cylinder misfire is occurring. Common causes include Faulty Spark Plug #12, Clogged or faulty Fuel Injector #12, Faulty Ignition Coil #12. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0312 indicates Cylinder 12 Misfire Detected.
Common causes: Common causes include Faulty Spark Plug #12, Clogged or faulty Fuel Injector #12, Faulty Ignition Coil #12.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 12,941

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Apr 09, 2023

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
Comments
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Code P0312 Description

The Engine Control Module (ECM) uses information from the crankshaft position sensor and the camshaft position sensor to determine when an engine cylinder misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM can detect individual cylinder misfire events.
Extreme cylinder misfire events can cause catalytic converter damage. The malfunction indicator lamp (MIL) will flash when the conditions for catalytic converter damage are present. The Diagnostic Trouble Codes (DTC) P0312 correspond to cylinders 12. When the ECM detects that one or more specific cylinders are misfiring, the DTC for the respective misfiring cylinder will set, and up to 2 of the corresponding fuel injectors are disabled for a minimum of 30 s. The ECM will then re-enable the fuel injector and, after approximately 200 engine revolutions, will determine if the misfire is still present. If the misfire is still present, the ECM will disable the fuel injector again repeating the process. If the misfire is not present, the fuel injector will remain enabled by the ECM.

OBDII Code P0312 - Cylinder 12 Misfire Detected - AutoCodes.com — P0312 Code - Cylinder 12 Misfire Detected

What does this mean?

What are the Possible Causes of the DTC P0312?

Faulty Spark Plug #12
Clogged or faulty Fuel Injector #12
Faulty Ignition Coil #12
Fuel Injector #12 harness is open or shorted
Fuel Injector #12 circuit poor electrical connection
Ignition Coil #12 harness is open or shorted
Ignition Coil #12 circuit poor electrical connection
Insufficient cylinder 12 compression
Incorrect fuel pressure
Intake air leak

How to Fix the DTC P0312?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

The P0312 code means that cylinder #12 is misfiring or is randomly misfiring. Start by checking for intake leaks and if no leaks are found the next step is to replace the spark plugs on cylinder #12. If the problem persists more tests need to be done to diagnose the problem. See "Possible Causes" for the most common problems.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0312 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0312 code?

Need more information on how to fix the P0312 code? Get Access to Factory Service Manuals

Need Help with the Code?

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Information for Specific Makes

P0312 Mercedes-Benz — Cylinder 12 Misfire Detected
P0312 Volkswagen — Cylinder 12 Misfire Condition

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.