High Exhaust Temperature (HET)
This code indicates that the exhaust temperature is too high for safe operation.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The exhaust system is getting too hot, which can damage components like the turbocharger or exhaust after-treatment systems.
What the computer is actually seeing
The Engine Control Module (ECM) measures exhaust temperature through a sensor and flags the code when it exceeds a specific threshold, usually around 1,200°F (650°C) for extended periods.
What a healthy reading looks like
Normal exhaust temperatures should range between 600°F to 1,200°F (316°C to 650°C) under normal operating conditions.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect exhaust temperature sensor wiring and connector for damage or corrosion. Decision: If good, go to next step; if bad, repair/replace as needed.
- 22. Check the exhaust temperature reading with a scan tool. Decision: If normal (600°F - 1,200°F), the code may be valid but related to other issues; if high, continue diagnostics.
- 33. Inspect the condition of the DPF and EGR systems for clogs. Decision: Clean or replace as necessary based on inspection results; if clear, proceed to next step.
- 44. Monitor fuel rail pressure and injector performance to verify correct fuel delivery. Decision: If fuel pressure is excessive, address injectors/fuel system; if normal, continue troubleshooting.
- 55. Examine turbocharger for proper operation and boost levels. Decision: If turbo is faulty, replace; if good, further system analysis may be required.
Common causes
- Faulty exhaust temperature sensor
- Exhaust restriction (clogged DPF or EGR)
- Fuel system issues (over-fueling)
- Turbocharger failure
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
No, it's not safe. High exhaust temperatures can lead to serious engine damage.
Will the code come back after I fix it?
If the underlying issue is resolved, the code should stay off.
Why does this code pair with SPN 1543?
SPN 1543 refers to a fuel system issue, which can cause excessive exhaust temperatures if the engine runs rich.
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