P0473 Exhaust Pressure Sensor "A" Circuit High Input

The P0473 trouble code means the engine control module (ECM/PCM) has detected an abnormally high electrical signal from the Exhaust Pressure Sensor "A" circuit.

The important word here is “High.” In this code, “high” primarily refers to the electrical voltage/signature of the sensor circuit, not necessarily excessively high exhaust pressure.

This distinction is important because a vehicle can have normal exhaust pressure while still setting P0473 if the sensor signal wire is shorted to voltage, the sensor has an internal fault, or the reference/ground circuit is abnormal.

What Does the Exhaust Pressure Sensor Do?

The exhaust pressure sensor measures pressure within the exhaust system and sends this information to the ECM.

The ECM can use exhaust-pressure information for several purposes, including:

• EGR control

• Turbocharger control

• DPF monitoring

• DPF regeneration

• Exhaust flow calculations

• Emissions control

• Detecting exhaust restrictions

On diesel engines, the sensor can be particularly important for monitoring the exhaust system and determining whether exhaust backpressure is within the expected range.

The sensor is often connected to the exhaust system through a pressure tube or hose.

Depending on the engine design, the sensor may measure:

• Exhaust manifold pressure

• Pre-DPF pressure

• Pressure before or after a particular exhaust component

• Differential pressure

• Another manufacturer-specific exhaust pressure

Therefore, the exact location and function of Sensor A depend on the vehicle.

What Does “Circuit High Input” Mean?

P0473 indicates that the ECM is seeing a higher-than-expected electrical signal from the Exhaust Pressure Sensor A circuit.

A typical pressure sensor may use:

• A reference voltage

• A ground

• A signal wire

The sensor converts pressure into an electrical signal.

If the ECM expects the signal to remain within a certain range but sees a voltage that is too high, it can store P0473.

Possible causes include:

• Signal wire shorted to voltage

• Faulty exhaust pressure sensor

• Open or high-resistance ground

• Incorrect reference voltage

• Damaged wiring

• Corroded connector

• Poor terminal contact

• Blocked or damaged pressure tube

• Incorrect sensor installation

• Exhaust pressure genuinely higher than expected on some systems

The exact diagnostic interpretation depends on the sensor design.

Symptoms of P0473

Possible symptoms include:

• Check Engine Light

• Reduced engine power

• Poor acceleration

• Turbocharger performance problems

• Increased fuel consumption

• EGR operation problems

• DPF regeneration problems

• More frequent regeneration attempts

• Limp-home mode

• Increased exhaust smoke

• Rough engine operation in some cases

Some vehicles may show no obvious drivability symptoms.

The ECM may simply substitute a calculated or default exhaust-pressure value and continue operating the engine.

Common Causes of P0473

Faulty Exhaust Pressure Sensor

The sensor itself can develop an internal electrical failure and produce a signal that is higher than expected.

This is one possible cause, but the sensor should not automatically be replaced simply because P0473 is present.

Signal wire shorted to voltage

This is an important possibility.

If the signal wire contacts a voltage source, the ECM may see a continuously high signal.

For example:

Signal wire damaged → contacts power supply → sensor signal becomes high → P0473

Poor sensor ground

A sensor needs a reliable ground reference.

If the ground circuit has excessive resistance, the sensor's output can become abnormal.

This is why the sensor ground should be tested under the appropriate conditions rather than simply checking continuity.

Damaged wiring

Exhaust pressure sensor wiring can be exposed to:

• High engine temperatures

• Vibration

• Oil

• Moisture

• Chafing

A damaged wire can create a high-input condition.

Corroded connector

A connector with corrosion or poor terminal contact can alter the sensor signal.

Look for:

• Green or oxidized terminals

• Water intrusion

• Loose pins

• Bent terminals

• Oil contamination

• Heat damage

Blocked pressure tube

The sensor may be electrically healthy while the pressure tube connected to it is blocked by:

• Carbon

• Soot

• Condensation

• Oil

• Other deposits

A blocked tube can cause the sensor to receive an incorrect pressure signal.

However, a blocked pressure tube does not necessarily create a high electrical voltage by itself, so the electrical and pressure sides should be tested separately.

Can High Exhaust Pressure Cause P0473?

It can, depending on the vehicle's diagnostic strategy, but this should not be assumed.

P0473 specifically identifies a high sensor input.

That means the ECM is primarily reporting an electrical signal that is higher than expected.

If the sensor is functioning correctly and actual exhaust pressure is genuinely excessive, the sensor output can naturally increase.

Possible causes of genuinely high exhaust pressure include:

• Restricted DPF

• Restricted catalytic converter

• Collapsed exhaust component

• Severe carbon buildup

• Damaged exhaust system

• Other exhaust-flow restrictions

Therefore, when sensor electrical testing is normal but the reported pressure is genuinely high, the exhaust system itself should be investigated.

How Is P0473 Diagnosed?

A proper diagnosis should separate two possibilities:

Is the sensor producing an incorrect high electrical signal?

or

Is the sensor correctly reporting genuinely high exhaust pressure?

That distinction is the heart of P0473 diagnosis.

1. Scan for Additional Codes

Start by checking all available control modules.

Look for related codes involving:

• Exhaust pressure

• DPF

• EGR

• Turbocharger

• Exhaust temperature

• Intake pressure

• Sensor reference voltage

• Sensor ground

• System voltage

If several sensors report unusually high values at the same time, a shared reference or ground problem becomes more likely.

2. Check Freeze-Frame Data

Determine when P0473 was recorded.

Useful information includes:

• Engine RPM

• Engine load

• Coolant temperature

• Vehicle speed

• Exhaust pressure

• Exhaust temperature

• DPF status

• EGR command

• Turbocharger pressure

• Battery/system voltage

If the code appears only under high engine load, the actual exhaust-pressure condition becomes more important.

If it appears immediately after the ignition is switched on, before the engine has generated meaningful exhaust pressure, an electrical sensor/circuit problem becomes much more suspicious.

3. Compare the Sensor Reading With Engine Conditions

Look at the exhaust-pressure sensor value with the engine OFF and then while the engine is running.

With the engine off, the sensor should generally report a value consistent with the applicable atmospheric/reference pressure for that system.

If the scan tool already shows an implausibly high exhaust pressure before the engine starts, that strongly suggests a sensor, wiring, reference or ground problem rather than genuinely high exhaust pressure.

This is one of the most useful observations when diagnosing P0473.

Check the Sensor Signal

If the sensor uses a conventional analog signal, measure the signal according to the manufacturer's specifications.

Check:

• Reference voltage

• Ground

• Signal voltage

Do not assume that every exhaust pressure sensor uses exactly the same voltage range.

The expected signal must be obtained from the specific vehicle's technical information.

Check for a Short to Voltage

Because P0473 is a high-input code, inspect the signal circuit for unintended contact with a power source.

A damaged harness may cause:

Signal wire → contact with supply voltage → high sensor input → P0473

This can be particularly likely when wiring has been routed near hot exhaust components.

Check the Sensor Ground

A poor ground can cause the sensor signal to become inaccurate.

Perform the appropriate voltage-drop or ground-circuit test while the sensor is operating.

Do not rely only on a simple continuity check.

A wire can have continuity and still have excessive resistance under load.

Inspect the Pressure Tube

If the sensor uses a pressure hose or metal pressure tube, inspect it carefully.

Look for:

• Carbon blockage

• Soot

• Cracks

• Leaks

• Kinks

• Condensation

• Oil contamination

A damaged or blocked tube can cause the pressure reaching the sensor to differ significantly from the actual exhaust pressure.

Check for Exhaust Restriction

If the sensor and its electrical circuit test correctly but the pressure reading remains genuinely high, investigate the exhaust system.

Possible restrictions include:

• DPF blockage

• Catalytic converter restriction

• Collapsed exhaust pipe

• Severe soot accumulation

• Damaged internal exhaust components

A restricted exhaust system can create excessive backpressure and lead to other symptoms such as poor acceleration and reduced engine power.

P0473 and DPF Regeneration

On diesel vehicles, P0473 can have an important relationship with the DPF system.

The ECM may use exhaust pressure as one of several parameters to evaluate:

• DPF loading

• Exhaust restriction

• Regeneration conditions

• Exhaust flow

If the exhaust pressure sensor reports an implausibly high value, the ECM may have difficulty determining whether the DPF is actually restricted.

This can potentially result in:

• Failed regeneration

• Repeated regeneration attempts

• Increased DPF loading

• Reduced engine power

• Additional DPF-related fault codes

However, a P0473 code does not by itself prove that the DPF is clogged.

Can a Blocked DPF Cause P0473?

Yes, potentially.

A severely restricted DPF can cause genuine exhaust backpressure to increase.

If the pressure sensor is operating correctly, the sensor can report that higher pressure.

But the diagnostic sequence should still establish whether the sensor signal is accurate.

If the sensor reports extremely high pressure even with the engine OFF, a blocked DPF cannot explain that reading.

That would point much more strongly toward an electrical or sensor problem.

P0473 vs P0472

These codes are related but indicate different electrical conditions.

P0472 – Exhaust Pressure Sensor "A" Circuit Low Input

The ECM detects a lower-than-expected sensor input.

P0473 – Exhaust Pressure Sensor "A" Circuit High Input

The ECM detects a higher-than-expected sensor input.

The difference is primarily the direction of the electrical signal detected by the ECM.

P0473 vs P0474

P0474 – Exhaust Pressure Sensor "A" Circuit Intermittent

indicates an unstable or intermittent sensor-circuit condition.

P0473 instead indicates that the sensor input is too high.

An intermittent wiring problem can sometimes eventually produce a high-input code, but the diagnostic approach should follow the code that is currently being recorded and the actual live data.

P0473 vs P0475

These codes concern different components.

P0473 concerns the Exhaust Pressure Sensor "A" circuit.

P0475 concerns the Exhaust Pressure Control Valve "A" circuit.

The pressure sensor measures exhaust pressure.

The control valve regulates exhaust flow/backpressure.

They can interact as part of the same emissions strategy, but they should not be automatically treated as the same component.

Can P0473 Cause Limp Mode?

Yes, depending on the vehicle.

If the ECM cannot trust exhaust-pressure information, it may modify engine operation to protect the engine and emissions system.

Possible responses include:

• Reduced engine power

• Turbocharger limitations

• EGR changes

• DPF regeneration restrictions

• Limp-home operation

Not every vehicle will enter limp mode.

Is It Safe to Drive With P0473?

If the vehicle runs normally, short-distance driving may be possible, but the fault should not be ignored.

The risk depends on the actual cause.

A faulty sensor circuit may primarily affect emissions control.

A genuine exhaust restriction, however, can cause:

• Reduced power

• Excessive exhaust temperature

• Turbocharger stress

• Failed DPF regeneration

• Increasing exhaust backpressure

If the vehicle is losing significant power, entering limp mode, producing excessive smoke or showing rapidly increasing exhaust temperatures, it should be diagnosed promptly.

Should You Replace the Exhaust Pressure Sensor?

Not automatically.

Before replacing the sensor, verify:

• Reference voltage

• Sensor ground

• Signal voltage

• Wiring condition

• Connector condition

• Pressure tube condition

• Live-data plausibility

• Actual exhaust pressure where appropriate

If the electrical supply and wiring are correct but the sensor consistently produces an incorrect high signal, sensor replacement becomes much more reasonable.

If the sensor is reporting genuinely high pressure, replacing the sensor will not solve the underlying exhaust restriction.

Final Diagnostic Summary

P0473 – Exhaust Pressure Sensor "A" Circuit High Input means the ECM/PCM has detected an excessively high electrical signal from the Exhaust Pressure Sensor A circuit.

The code does not automatically mean that exhaust pressure itself is too high.

The most important diagnostic distinction is:

High electrical signal from a faulty circuit/sensor

versus

Correct sensor signal caused by genuinely high exhaust pressure.

A sensible diagnostic sequence is:

Scan for related codes → check freeze-frame data → compare live pressure data → inspect wiring/connectors → verify reference and ground → test signal circuit → inspect pressure tube → verify actual exhaust pressure → investigate exhaust restriction if necessary.

One especially useful clue is the sensor reading with the engine switched off. If the scan tool already shows an implausibly high exhaust-pressure value before the engine produces exhaust pressure, the sensor or its electrical circuit becomes a much stronger suspect.

The key question with P0473 is therefore not simply:

“Is the exhaust pressure high?”

It is:

“Is the sensor reporting high pressure because exhaust pressure is genuinely high, or is the ECM receiving an artificially high electrical signal?”