What Is P0470?
P0470 is stored when the ECU detects an abnormal signal from the exhaust back-pressure sensor. This sensor is fitted to most modern diesel engines and monitors the pressure in the exhaust system to help control the DPF (diesel particulate filter) regeneration cycle and EGR operation.
When the sensor reading falls outside the expected range for the current operating conditions, the ECU logs P0470 and may illuminate the engine management light. In many cases the sensor itself has failed, but wiring problems and a blocked DPF are also common culprits.
Common Symptoms
- Engine management light on
- DPF regeneration not completing (DPF warning light)
- Reduced engine performance or limp mode
- Increased fuel consumption
- Erratic idle on some diesels
- EGR system operating incorrectly
Common Causes
OBD Fault Code Plain English Guide
- 100 most common UK fault codes in plain English
- A severity rating for every code so you know what can wait
- Causes and next steps listed for each fault
Instant PDF download · works on phone, tablet or PC · 7-day money-back guarantee
How to Diagnose P0470
Scan for Additional Codes
Before focusing on P0470, check for DPF, EGR, or turbo-related codes stored alongside it. Related codes often point to the root cause rather than the sensor being the primary fault.
Inspect the Sensor and Pipe
Locate the exhaust back-pressure sensor - usually on the exhaust manifold or DPF housing. Disconnect the small rubber or plastic pressure pipe and check for soot blockage. Clear any blockage with compressed air.
Check Sensor Wiring
Inspect the connector for corrosion, bent pins, or damage. Back-probe the signal wire with a multimeter while the engine runs. Voltage should respond when you rev the engine. No change = failed sensor or open circuit.
Test Sensor Reference Voltage
With the connector plugged in and ignition on, back-probe the reference voltage pin. You should read 5V from the ECU. No voltage indicates a wiring fault between the ECU and sensor.
Replace the Sensor
If the pipe is clear and wiring checks out, replace the sensor. They are inexpensive and usually accessible. Clear the code and road test to confirm the fix.
Check DPF Condition
If the fault returns after sensor replacement, have the DPF pressure drop tested across it. A blocked DPF will overload any sensor and cause this code to return repeatedly.
Verdict
Start by clearing the sensor pressure pipe of any soot blockage - this alone fixes many P0470 faults. If the pipe is clear, test the wiring before replacing the sensor. Always check DPF health if the code returns.
P0471 - Implausible Rather Than Silent
P0470 and P0471 are two moods of the same exhaust back pressure sensor. P0470 means the circuit has failed outright - the ECU hears nothing sensible at all. P0471 means the sensor still talks, but what it says does not match the conditions: pressure readings that wander at idle, stay frozen under load, or disagree wildly with what the other exhaust sensors imply. Everything on this page about location, wiring and testing applies to both codes.
P0471 has one suspect that beats the sensor itself: the narrow metal pipe that connects it to the exhaust. It carries hot, sooty gas, and it slowly cokes shut - the sensor then reads a lazy, damped version of reality, which is exactly the implausibility the ECU flags. Pull the pipe off and check it is clear before spending on the sensor; on diesels this pipe is the answer more often than the electronics. A blocked pipe also lies to the DPF logic, so an unexplained P2453 or DPF warning alongside P0471 strengthens the case for soot in the plumbing.
