P0473
PowertrainExhaust Pressure Sensor High
The exhaust pressure sensor measures how much back-pressure is building up in the exhaust, and on a diesel it's the ECU's main way of knowing whether the DPF is getting clogged. P0473 means that sensor is sending back a voltage that's too high, usually higher than the 5V reference it should ever see, which points the finger at the wiring or the sensor itself rather than the actual pressure. When the ECU can't trust the reading, it often drops the car into limp mode and refuses to run a DPF regeneration. So you end up with a soot-laden filter that can't clean itself, and a sensor fault that needs sorting before that turns into a much bigger bill.
ⓘ Information only. This page provides general educational information about fault code P0473. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0473 mean?
P0473 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Exhaust Pressure Sensor High.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light on, sometimes the first and only sign
- • Car going into limp mode, especially on diesels with a turbo and DPF
- • Sluggish acceleration and a general lack of power
- • DPF regeneration won't complete, so the soot count keeps climbing
- • Rough idle once the engine's warmed up
- • Black smoke from the exhaust on some cars when it's running rich
- • Fuel economy down by a noticeable margin
Possible causes
Causes commonly associated with P0473, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Faulty exhaust pressure sensor with an internal electrical fault, common as these sit in a hot, dirty spot and don't last forever
- 2. Damaged wiring in the sensor circuit, frayed, burnt or chafed where the loom runs near the exhaust heat
- 3. Short to battery voltage, so the ECU sees 12V where it expects a 5V reference. This is what most directly causes the high-voltage reading
- 4. Corroded or damaged connector at the sensor, water and road salt get into these easily underneath the car
- 5. Blocked or soot-packed pressure tube feeding the sensor, which can throw the reading right off
- 6. Intermittent open circuit leaving the signal wire floating high, often the cause of a fault that comes and goes
- 7. Faulty PCM, but that's rare and the last thing to suspect, not the first
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Get the car on a scan tool and read the live exhaust pressure value alongside any sibling codes like P0471 or P0472. A reading pinned at the top of the scale with the engine off tells you it's electrical, not real pressure
- 2. Have a proper look at the sensor, its connector, the wiring and the pressure tube. You're hunting for melted insulation, green corrosion in the plug, or a tube packed solid with soot
- 3. Unplug the sensor harness and check the reference supply with a multimeter, ignition on. You should see roughly 5V. If you find 12V there, you've got a short to battery voltage feeding the high reading
- 4. Back-probe the signal wire with the sensor connected and ignition on. Sitting consistently above 4.8V to 5.0V confirms the high-circuit condition the code is flagging
- 5. Check for a manufacturer software update, some makers issued a PCM recalibration for over-sensitive readings on certain diesels
- 6. Clear the code, take it for a proper drive and watch whether it comes straight back or stays away, which separates a hard fault from an intermittent connection
Common questions about P0473
Will my car fail the MOT with a P0473 stored? +
The code on its own isn't a fail, but if the engine warning light is glowing when the tester looks at it, that's a fail on the MIL check regardless of what the code is. The bigger problem on a diesel is the knock-on effect: if the sensor fault has stopped the DPF regenerating, the emissions and smoke test can fail too because the filter's clogged. Fix the sensor, let the car run a successful regen, and clear the light before you book it in.
What's this going to cost me to put right? +
The sensor itself is fairly cheap, usually £30 to £90 for the part, and an independent garage will have it swapped and the code cleared for somewhere in the low hundreds all in. A main dealer will charge more, often pushing toward the mid hundreds once you add their labour rate. Where it gets expensive is if the wiring or connector is the real fault and someone has to spend an hour tracing a short, or worse, if the DPF has loaded up with soot while the sensor was lying and now needs forced regeneration or replacement.
How do I tell whether it's the sensor or the wiring on my car? +
Start with the live data. If the pressure reading is stuck at maximum with the engine switched off, no exhaust is flowing so that voltage is electrical, not real. From there it's the multimeter that splits it: unplug the sensor and check the reference feed. A clean 5V means the supply's fine and you're looking at the sensor or its signal wire. Finding 12V means the wiring has shorted to battery voltage and a new sensor won't fix anything. Wiggle the loom near the exhaust while watching the data, because a reading that jumps about points to a chafed wire rather than a dead sensor.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →