P0671 Code: Meaning, Symptoms, Causes & Fix

Overview

Code P0671 indicates a fault in Cylinder 1 Glow Plug Circuit, typically within powertrain controls.

Symptoms

increased fuel use
reduced performance
rough operation in certain conditions

Common causes

Disconnected or loose connector affecting cylinder 1 glow plug circuit
Broken terminal inside harness
Connector pin damage/corrosion or harness stress near related components

How to diagnose P0671

Confirm P0671 and capture freeze-frame data with a professional scan tool.
Inspect wiring, connectors, and grounds related to cylinder 1 glow plug circuit for obvious defects.
Use a continuity test from module pin to component to identify opens/high resistance.
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 P0671

Moderate: This code is moderate severity: the vehicle may still operate, but fault progression can increase repair cost over time.

Can you drive with P0671?

Most vehicles can be driven short-term with P0671, but postpone heavy load/highway driving until repaired.

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 (open) in the cylinder 1 glow plug circuit circuit/system.
Apply the required relearn/adaptation procedure if specified by service information.
Road-test and verify P0671 remains cleared under the conditions that originally set the code.

Fix options

Repair open circuit and secure connector lock.
Restore continuity and verify pin tension.
Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$200-$900

Common mistakes when diagnosing P0671

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.

P0671 in common vehicles

P0671 appears across makes such as Mazda, Subaru, Lexus, Jeep. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.

Frequently asked questions

What causes P0671?

P0671 is commonly set by open faults affecting cylinder 1 glow plug circuit.

How much does it cost to fix P0671?

For P0671, repair costs are typically $200-$900 depending on exact root cause, labor rates, and part quality.

Can I clear P0671 without repair?

You can clear P0671 temporarily, but the code usually returns until the underlying fault is corrected.