P1408 Code: Meaning, Symptoms, Causes & Fix

Overview

Symptoms

• rough idle under load
• failed emissions test readiness
• increased fuel consumption

Common causes

• Sensor output out of expected lower range affecting egr flow out of self test range
• High circuit resistance
• Connector pin damage/corrosion or harness stress near related components

How to diagnose P1408

1. Confirm P1408 and capture freeze-frame data with a professional scan tool.
2. Inspect wiring, connectors, and grounds related to egr flow out of self test range for obvious defects.
3. Compare live data against expected lower threshold and verify ground/reference circuits.
4. Check for related DTCs to identify the root-cause chain before replacing parts.
5. After repair, clear codes and confirm readiness monitors complete without recurrence.

Severity of code P1408

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

Can you drive with P1408?

Most vehicles can be driven short-term with P1408, 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)

1. Repair obvious wiring/connector faults first to prevent repeat parts replacement.
2. Address the root fault mode (low) in the egr flow out of self test range circuit/system.
3. Apply the required relearn/adaptation procedure if specified by service information.
4. Road-test and verify P1408 remains cleared under the conditions that originally set the code.

Fix options

• Replace failed sensor if signal remains low.
• Repair connector resistance issues.
• Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$180-$900

Common mistakes when diagnosing P1408

• 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.

P1408 in common vehicles

P1408 appears across makes such as Nissan, Hyundai, Kia, Volkswagen. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.

Frequently asked questions

What causes P1408?

P1408 is commonly set by low faults affecting egr flow out of self test range.

How much does it cost to fix P1408?

For P1408, repair costs are typically $180-$900 depending on exact root cause, labor rates, and part quality.

Can I clear P1408 without repair?

You can clear P1408 temporarily, but the code usually returns until the underlying fault is corrected.

Helpful tools

• Estimate repair cost
• Decode your VIN
• Calculate fuel cost