EGR Flow Excessive
The HINO-P0402 (Hino) diesel fault code means: EGR Flow Excessive. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- intermediate
- Estimated cost
- $400-$2,400
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Common Symptoms
- Reduced fuel economy
- Frequent DPF regens
- Coolant loss with no external leak (cooler crack)
- Hesitation off idle
- Check Engine Light with possible derate
Probable Causes (Ranked by Likelihood)
- EGR valve carbon seizure — very common J08 above 200K miles Very Likely
- EGR cooler soot-packed restricting flow Likely
- Cracked EGR cooler with coolant loss (later J08 TSBs) Possible
- EGR position sensor drift Possible
- Damaged EGR connector / heat-related pin corrosion Possible
Frequently Asked Questions
What does Hino code P0402 mean?
Hino diagnostic trouble code P0402 (EGR Flow Excessive) is a moderate-severity fault on Hino medium-duty diesel engines. It indicates a problem in the EGR system that should be verified with a scan tool (Hino DX3 / DX4) before replacing any parts.
Can I drive my Hino truck with P0402?
Short runs may be possible but do not ignore — Hino medium-duty aftertreatment faults cascade quickly into 5-mph derate or no-restart. Schedule diagnosis immediately.
How much does it cost to fix Hino P0402?
Estimated repair cost runs $400-$2,400. Sensor, wiring, and DEF-related repairs fall at the low end; DPF service, turbo, injector, and EGR cooler work fall at the high end and may require dealer-level programming.
What actually makes the computer set this EGR code?
California's heavy-duty OBD regulation sets the low-flow trip point where a decrease from the manufacturer's specified EGR rate would push NMHC, CO or NOx past 2.0 times the applicable standards, or PM past the standard plus 0.02 g/bhp-hr (Title 13 CCR 1971.1, section (e)(3.2.1)). Note the second route: it must also flag the case where the EGR system has hit its control limits and simply cannot reach the commanded flow — so this code can set with the valve working and the system still unable to deliver. This threshold comes from the heavy-duty OBD regulation, which covers 2010 and later heavy-duty engines. If your engine is in a pickup at or under 14,000 lb GVWR it is certified under the separate medium-duty rule instead, so treat this as the design intent rather than your engine's exact limit.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
Confirm P0402 on Hino DX3. Compare EGR actual vs commanded position at idle and cruise.
Remove EGR valve — heavy carbon is normal on J08; clean seat if free, replace if seized.
Pressure-test cooling system and monitor for coolant loss — cracked EGR cooler pushes coolant into the intake.
Inspect the EGR harness for heat-related damage where it routes near the turbo / exhaust manifold.
After mechanical cleaning or replacement, clear code and run a forced regen to burn off residual soot.
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 P0402 as a generic OBD-II code)
P0402 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
Commonly Affected Vehicles
- Hino 155 / 155h with J05 5.1L
- Hino 195 / 195h (hybrid) with J05D 5.1L
- Hino 258 / 258LP / 268 with J08 7.7L
- Hino 338 / 338CT with J08 7.7L
- Hino 358 / 358CT (post-2019 J-series / A09C)
- Toyota Dyna / Hino-branded export chassis with J05/J08
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