P0408

Q: What does OBD2 code P0408 mean?

P0408 means: Exhaust Gas Recirculation Sensor B Circuit High. The secondary EGR position sensor (Sensor B) is reading a higher voltage than expected.

Exhaust Gas Recirculation Sensor B Circuit High

The secondary EGR position sensor (Sensor B) is reading a higher voltage than expected.

SeverityModerate

CategoryEmissions

Est. Repair Cost$150-$350

Code TypePowertrain

DIY RepairYes

⚡ Common Causes

›Faulty EGR sensor
›Wiring short circuit
›Carbon buildup affecting valve position

⚠️ Symptoms

›Check engine light
›Possible rough idle
›Reduced fuel economy

✅ How to Fix — Step by Step

Step 1:Clean EGR valve and passages
Step 2:Inspect wiring for shorts
Step 3:Test sensor voltage
Step 4:Replace sensor if faulty

🔧 Diagnostic Tools Required

✔OBD-II Diagnostic Scanner
✔Digital Multimeter
✔Basic Hand Tools
✔Flashlight
✔Vehicle Service Manual

Using the correct diagnostic tools helps identify the root cause of P0408 before replacing parts unnecessarily. Always confirm the fault using live data and manufacturer-recommended diagnostic procedures.

💡 Pro Tip: Always clean the EGR valve before replacing the position sensor - carbon buildup is the more common and cheaper fix.

Repair Cost Estimate

Full Repair Estimate

$150-$350

DIY Possible?

YES

Severity

Moderate

Frequently Asked Questions

What does OBD2 code P0408 mean?+

P0408 stands for Exhaust Gas Recirculation Sensor B Circuit High. The secondary EGR position sensor (Sensor B) is reading a higher voltage than expected.

What causes code P0408?+

Faulty EGR sensor; Wiring short circuit; Carbon buildup affecting valve position

How do I fix code P0408?+

Clean EGR valve and passages; Inspect wiring for shorts; Test sensor voltage; Replace sensor if faulty

How much does it cost to fix P0408?+

Estimated repair cost for P0408 is $150-$350.

Is P0408 DIY-friendly?+

Yes — P0408 is generally DIY-friendly with basic tools.