Exhaust Gas Recirculation Sensor "B" Circuit High
The ISUZU-P0408 (Isuzu) diesel fault code means: Exhaust Gas Recirculation Sensor "B" Circuit High. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- intermediate
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What Are the Symptoms of ISUZU-P0408?
- Check Engine light
- EGR may be disabled
What Causes ISUZU-P0408? (Most Likely First)
- Sensor signal wire shorted to voltage, or an open ground High
- Failed EGR sensor "B" High
- Damaged or corroded connector Medium
Can I Still Drive with ISUZU-P0408?
Short distances only. ISUZU-P0408 is rated moderate severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What does P0408 mean on a Isuzu?
P0408 means Exhaust Gas Recirculation Sensor "B" Circuit High. The EGR sensor "B" signal is above the range the control module expects.
Is P0408 a Isuzu-specific code?
No. P0408 is a generic OBD-II code defined by SAE J2012, so it means the same thing on any vehicle that sets it. The exact conditions Isuzu uses to set it on its diesels are in Isuzu service information.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose ISUZU-P0408?
Identify which EGR sensor is "B" on this engine in the service information.
Check the sensor ground and look for a short to voltage on the signal wire.
Inspect the connector and harness.
Sources 3
This page is built from documented references. Verify against your own service info before repair work.
- California Code of Regulations, Title 13 section 1971.1 (Heavy-Duty OBD)malfunction criteria, section (e)
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
- SAE J2012Diagnostic Trouble Code Definitions (defines P0408 as a generic OBD-II code)
P0408 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
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