Cause
Faulty exhaust back pressure sensor
The sensor measuring pressure in the exhaust upstream of whatever restricts it, and on a modern diesel it is one of the most consequential readings on the engine. The module uses it to decide when the particulate filter is loaded, and a wrong reading therefore does not just store a code — it drives real decisions about regeneration that are expensive to get wrong in either direction.
Reading high, it triggers regenerations the filter does not need, which dumps fuel into the exhaust, dilutes the engine oil and shortens the life of everything downstream. Reading low, it lets a genuinely loaded filter keep loading until the restriction is bad enough to affect running. Either way the sensor is believed and the filter is blamed.
It rarely fails as an element. It is mounted away from the heat and connected to the exhaust by a small steel pipe, and that pipe is the part that fails — sooted solid, corroded through, or kinked when something nearby was removed. Check the pipe is clear before condemning the sensor: a blocked pipe means the sensor is faithfully reporting a pressure that stopped changing, which is why the reading looks plausible and flat rather than obviously wrong.
Typically a moderate job.
Some of these codes mean you should stop driving
1 of the 5 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (5)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0470 Exhaust Pressure Sensor A Circuit Likely for this code Moderate
- P0471 Exhaust Pressure Sensor A Circuit Range/Performance Likely for this code Moderate
- P0472 Exhaust Pressure Sensor A Circuit Low Likely for this code Moderate
- P0473 Exhaust Pressure Sensor A Circuit High Likely for this code Stop driving Moderate
- P0474 Exhaust Pressure Sensor A Circuit Intermittent/Erratic Moderate
Information, not instruction
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