P0408
PowertrainEgr Systemmoderate severityExhaust Gas Recirculation Sensor B Circuit High
What P0408 Means
The PCM detects a high voltage signal from EGR sensor B. A short to voltage or open ground is often the cause.
Symptoms
- Check engine light on
- Rough idle or hesitation
- Higher emissions
Common Causes
- Short to voltage in wiring
- Faulty EGR position sensor B
- Open ground circuit
- Corroded connector
Diagnostic Steps
- Retrieve codes and freeze frame
- Measure EGR sensor B signal voltage
- Check for short to power and ground integrity
- Replace sensor or repair wiring
🔌 Don't have a code reader?
Any of these will read and clear this code — pick by how deep you want to go.
Budget handheld~$40
ANCEL AD410 →
No-phone-needed handheld — reads, clears, live data, freeze frame.
✓ ANCEL official store
Serious DIY~$100
BlueDriver Pro →
Enhanced codes (ABS, airbag, TPMS) plus repair reports.
SHOP FAVORITEShop-grade tablet~$300
Autel MaxiCOM MK808S →
Bidirectional tests, service resets, all systems.
✓ Autel official store
Pro diagnostics$1,500+
Autel MaxiSys MS906 Pro →
Full-system pro platform — topology mapping, ECU coding, the works.
✓ Autel official store
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