Measured Exhaust Flow Too High
The exhaust flow detected is higher than expected for the engine's operating conditions.
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)
Your truck's computer is seeing more exhaust coming out than it thinks should be, which can happen if there's a problem with the exhaust system or sensors.
What the computer is actually seeing
The Engine Control Module (ECM) monitors the exhaust flow using a sensor. It expects certain flow rates under various conditions. If it sees a flow rate that exceeds its predetermined limit, it sets the SPN 4380 code.
What a healthy reading looks like
Normal exhaust flow rates are typically between 500-1500 kg/h depending on the engine load and RPM, but this can vary by engine type.
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 the exhaust flow sensor's electrical connector for corrosion or damage. If damaged, repair or replace the connector. Decision Point: Is the connector good? If No, fix the connector. If Yes, proceed to step 2.
- 22. Check for exhaust leaks before the exhaust flow sensor. Use a smoke machine or listen for hissing sounds. Decision Point: Are there any leaks? If Yes, repair the leak. If No, proceed to step 3.
- 33. Test the exhaust flow sensor. Using a scan tool, monitor the PID data for exhaust flow while revving the engine to check for valid readings. Decision Point: Is the sensor showing expected readings? If No, replace the exhaust flow sensor. If Yes, proceed to step 4.
- 44. Inspect the DPF for blockages. If applicable, perform a DPF regeneration cycle. Decision Point: Is the DPF clear? If No, clean or replace the DPF. If Yes, check for other underlying issues.
Common causes
- Faulty exhaust flow sensor
- Exhaust leaks upstream of the sensor
- Blocked or damaged DPF (Diesel Particulate Filter)
- Wiring issues or connector faults on the exhaust flow sensor
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It’s not recommended to drive for long with this code. You might lose power, and it can lead to further exhaust system damage.
Will this code come back after clearing?
If the underlying issue isn't resolved, the code is likely to return.
Why does this code pair with SPN 4379?
Both codes relate to exhaust flow issues; one indicates high flow, while the other may indicate related sensor problems.
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