P0312 Code: Meaning, Symptoms, Causes & Fix

Overview

Code P0312 indicates a fault in Cylinder 12 Misfire Detected, typically within powertrain controls.

Symptoms

increased fuel use
reduced performance
rough operation in certain conditions

Common causes

Component failure in the monitored system affecting cylinder 12 misfire detected
Electrical fault in the affected circuit
Connector pin damage/corrosion or harness stress near related components

How to diagnose P0312

Confirm P0312 and capture freeze-frame data with a professional scan tool.
Inspect wiring, connectors, and grounds related to cylinder 12 misfire detected for obvious defects.
Use freeze-frame and live data to isolate whether the issue is electrical, mechanical, or control logic.
Check for related DTCs to identify the root-cause chain before replacing parts.
After repair, clear codes and confirm readiness monitors complete without recurrence.

Severity of code P0312

High: This code is high severity because the affected system can directly impact drivability, safety, or catalyst/engine protection.

Can you drive with P0312?

Driving with P0312 should be limited to a short trip for diagnosis/repair. Continued driving can cause expensive secondary damage.

If the warning lamp is flashing or drivability/safety is affected, avoid driving and diagnose immediately.

How to fix it (step-by-step)

Repair obvious wiring/connector faults first to prevent repeat parts replacement.
Address the root fault mode (generic) in the cylinder 12 misfire detected circuit/system.
Apply the required relearn/adaptation procedure if specified by service information.
Road-test and verify P0312 remains cleared under the conditions that originally set the code.

Fix options

Clear code and confirm through drive cycle.
Test component operation and replace if faulty.
Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$400-$2000

Common mistakes when diagnosing P0312

Replacing parts without verifying voltage, ground, and signal integrity first.
Ignoring related stored/pending codes that indicate upstream faults.
Skipping post-repair verification drive cycle and readiness checks.

P0312 in common vehicles

P0312 appears across makes such as BMW, Mercedes-Benz, Audi, Volvo. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.

Frequently asked questions

What causes P0312?

P0312 is commonly set by generic faults affecting cylinder 12 misfire detected.

How much does it cost to fix P0312?

For P0312, repair costs are typically $400-$2000 depending on exact root cause, labor rates, and part quality.

Can I clear P0312 without repair?

You can clear P0312 temporarily, but the code usually returns until the underlying fault is corrected.