P0471
Universal (All Makes) Vehicle (OBD-II)
Severity: ModerateWhat Does This Error Mean?
P0471 means the exhaust pressure sensor is giving readings that don't match what the engine computer expects. The sensor is working — it's producing a signal — but that signal is out of the expected range for the current engine conditions. This is a 'performance' fault, meaning the sensor is responding, just not correctly. You may notice black smoke, poor power, or increased fuel consumption on diesel engines.
Affected Models
- Diesel trucks and SUVs (2003+)
- Ford F-250/F-350 with 6.0L and 6.4L Power Stroke
- Dodge Ram with 5.9L and 6.7L Cummins diesel
- Chevy/GMC with LMM and LML Duramax
- VW and Mercedes diesel cars
Common Causes
- Exhaust pressure sensor tube or port is clogged with carbon, giving skewed readings
- Small exhaust leak between the sensor and the measuring point affecting pressure
- Sensor is contaminated with diesel soot and responding sluggishly
- Wiring or connector issue causing intermittent signal dropouts
- Sensor is beginning to fail and no longer responds accurately to pressure changes
How to Fix It
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Find the exhaust backpressure sensor — usually on the exhaust manifold, the EGR system, or near the diesel particulate filter. Check your repair manual for your specific model.
On Ford Power Stroke engines, this sensor is often near the up-pipe. On Cummins engines, look at the exhaust manifold.
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Disconnect the sensor and inspect the small port or tube it connects to. Use compressed air or a thin wire to clear out carbon soot that may be blocking it.
A blocked port is the leading cause of P0471. The sensor cannot read pressure accurately if the passage is clogged.
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Visually inspect the wiring harness and connector pins for corrosion or damage. Use electrical contact cleaner on the connector, reconnect firmly, and clear the code.
Vibration loosens connectors on diesel engines over time. A loose connection can cause erratic sensor readings.
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Check for any exhaust leaks near the sensor — listen for ticking or hissing sounds with the engine running. Even a small leak changes the pressure reading and triggers P0471.
Look for sooty black residue around exhaust joints and gaskets, which indicates a leak point.
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If all physical checks pass, replace the exhaust pressure sensor. Clear the code and drive a full drive cycle to confirm it does not return.
Sensors on high-mileage diesels are relatively inexpensive. If the vehicle has over 150,000 miles, replacement is often the right call.
When to Call a Professional
If you've cleaned the sensor port and checked wiring without success, have a diesel specialist diagnose it. A diesel shop with proper scan tools can monitor live exhaust pressure data to pinpoint the fault. Expect $150 to $300 for diagnosis and sensor replacement.
Frequently Asked Questions
What is the difference between P0470 and P0471?
P0470 is a general malfunction — the sensor signal is completely wrong or absent. P0471 is a performance fault — the sensor is working but its readings don't match what the engine expects. Both codes have the same common fixes: clean the port, check wiring, replace the sensor.
Can a clogged DPF cause P0471?
Yes, indirectly. A heavily clogged diesel particulate filter raises exhaust backpressure significantly. If the pressure is much higher than the sensor's normal range, the computer may log P0471. Check for a P2002 or P2452 code alongside P0471, which would point to a DPF problem.
How do I test the exhaust pressure sensor?
With the engine off, the sensor should read near zero or atmospheric pressure. With the engine idling, it should show a small positive pressure. Under load, pressure rises. If the reading is stuck, pegged, or jumpy, the sensor has failed. A bi-directional scan tool can command the sensor to check its response.