🚨 Code P0470: Exhaust Pressure Sensor Problem

🔧 Definition
This generic code relates to the exhaust pressure sensor (circuit “A”) and mainly applies to vehicles equipped with variable nozzle turbochargers (gasoline or diesel). Affected models:

• 🚚 Ford 6.0L Diesel (2005+), EcoBoost.
• 🚛 Cummins 6.7L (2007+), 3.0L (Nissan 2015+).
• 🚗 Mercedes 3.0L (2007+).

The PCM detects an inconsistency between the measured exhaust pressure and the intake/ambient pressure at startup. Possible issue: electrical failure (circuit) or mechanical (blockage, leak).

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⚠️ Related Codes

Code	Description
🔧 P0471	Sensor circuit range/performance abnormal.
🔌 P0472	Sensor circuit too low.
🔋 P0473	Sensor circuit too high.
🌀 P0474	Intermittent signal.

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🚨 Symptoms

• 📛 Check engine light on.
• 💨 Loss of power.
• 🔥 Particulate filter regeneration impossible (soot buildup).
• 🚫 Unable to start (if severe blockage).

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🔍 Possible Causes

• 🚮 Blockage in the sensor tube (carbon, debris).
• 🕳️ Air leak (EGR system, turbocharging, manifold).
• 📡 Faulty pressure sensor.
• 🤖 PCM failure (rare).

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🛠️ Diagnostic Procedures

1. 🔎 Check technical service bulletins (TSB)

• Consult manufacturer PCM software updates.

1. 🧹 Clean the sensor tube

• Disconnect the tube from the manifold.
• Blow air or use a wire to clear obstructions.

1. 🔌 Inspect wiring and connectors

• Look for exposed, burnt, or corroded wires.
• Clean terminals with 90% alcohol and a soft brush.
• Apply dielectric grease to protect contacts.

1. 🔧 Test the sensor (3 wires)

• Power wire (5V): Check with a multimeter (DVOM).
• Signal wire (5V): Measure voltage at rest.
• Ground: Test with a test light (12V).

1. 🔄 Check for air leaks

• Inspect turbocharger hoses and tighten clamps.

1. 📉 Reset the PCM

• Clear the code. If it returns, replace the sensor.

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⚡ Solutions

Step	Action
1️⃣ Cleaning	Unblock the tube and clean connectors.
2️⃣ Replacement	If the sensor is faulty, install a new one.
3️⃣ Repair	Repair damaged wires or replace the harness.
4️⃣ PCM	As a last resort, consult a pro to test the computer.

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💡 Pro Tip

• A forced regeneration may be needed after repair to clean the particulate filter.
• Use a high-end scanner (e.g., Snap-On, Autel) to access real-time sensor data.

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🚫 Risks of Ignoring the Code

• Damage to the particulate filter or catalyst.
• Engine overheating due to incorrect air-fuel mixture.
• High repair costs if the problem worsens.

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🔋 Key Takeaway
The exhaust pressure sensor is crucial for optimizing turbocharger performance and reducing emissions. Act quickly to avoid costly breakdowns! 🛠️🔧

P0471 Exhaust Pressure Sensor Range/Performance

What Does It Mean?

This generic powertrain/engine diagnostic code applies to all engines using variable nozzle turbochargers (gasoline or diesel), starting around 2005 on Ford trucks with 6.0L diesel engines, all Ford EcoBoost engines, and eventually leading to the Cummins 6.7L in 2007, the 3.0L in the Mercedes lineup in 2007, and more recently the Cummins 3.0L 6-cylinder in Nissan vans from 2015. This doesn’t necessarily mean you won’t get this code in a VW or other brand.

This code is strictly concerned with the incoming signal from the exhaust pressure sensor not matching the intake manifold pressure or ambient air pressure during key-on. This could be an electrical circuit fault or it could be mechanical.

The P0470 code may also be present along with P0471. The only difference between these two codes is the duration of the issue and the type of electrical/mechanical problem encountered by the sensor/circuit/engine controller. Troubleshooting steps may vary by manufacturer, gas or diesel, type of exhaust pressure sensor, and wire colors.

Related Exhaust Pressure Sensor Fault Codes:

P0470 Exhaust Pressure Sensor “A” Circuit
P0472 Exhaust Pressure Sensor “A” Circuit Low
P0473 Exhaust Pressure Sensor “A” Circuit High
P0474 Exhaust Pressure Sensor “A” Circuit Intermittent

Symptoms of a P0471 Engine Code May Include:

• Check Engine Light on
• Lack of power
• Unable to perform a manual regeneration
• If it is unable to perform regeneration.

Potential Causes

Typically, the causes for this code to set are:

• Blockage in the exhaust manifold tube to the pressure sensor
• Exhaust Gas Recirculation (EGR) system / air intake / boost air leaks
• Faulty exhaust pressure sensor
• A faulty Powertrain Control Module (PCM) might be the cause (very unlikely)

Diagnostic and Repair Procedures

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A good starting point is always to check for a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogram to address this issue, and it’s worth checking before finding out you’ve taken a long/wrong path.

Next, locate the exhaust pressure sensor on your specific vehicle. Once located, disconnect the tube connecting the sensor to the exhaust manifold. Try to blow through it. If you cannot, try to pass a small piece of wire through to dislodge the carbon trapped inside, causing the fault code you are experiencing. If you notice some water blown out, this could be the cause of the code.

If the tube is clear and free, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burns, or melted plastic. Separate the connectors and carefully inspect the terminals (the metal parts) inside the connectors. See if they look corroded, burnt, or perhaps greenish compared to the normal metallic color you are used to seeing. You can get electrical contact cleaner at any auto parts store if terminal cleaning is needed. If that’s not possible, find 91% rubbing alcohol and a soft plastic-bristled brush to clean them.

Then, let them air dry, get some dielectric silicone compound (the same kind used for bulb sockets and spark plug wires) and apply a small amount where the terminals make contact. Next, ensure the tube connecting the turbocharger to the intake manifold is not leaking. Visually inspect all tube connections around the turbocharger and intake manifold. Tighten all hose/band clamps.

Scan Tool

If you have a scan tool, clear the diagnostic codes from the memory and see if this code returns. If it does not, the connections were likely your problem.

If the code returns, we will need to test the sensor and its associated circuits. Typically, there are 3 wires at the exhaust pressure sensor.

Disconnect the harness going to the exhaust pressure sensor. With a Digital Volt-Ohm Meter (DVOM), test the 5V supply circuit going to the sensor to ensure it is powered (red wire to the 5V supply circuit, black wire to a good ground). If there are 12 volts at the sensor when there should be 5 volts, repair the wiring from the PCM to the sensor for a short to 12 volts, or possibly a faulty PCM.

If that’s okay, with a DVOM, check that the exhaust pressure sensor signal circuit is 5V (red wire to the sensor signal circuit, black wire to a good ground). If there is no 5 volts at the sensor, or if you see 12 volts at the sensor, repair the wiring from the PCM to the sensor, or again a faulty PCM.

If that checks out, verify that the exhaust pressure sensor ground is good. Connect a 12V test light to the battery positive (red terminal) and touch the other end of the test light to the ground circuit going to the exhaust pressure sensor circuit ground. If the test light does not illuminate, that would indicate a circuit problem. If it lights up, wiggle the wiring harness going to each sensor to see if the test light flickers, indicating an intermittent connection.

If all tests have passed so far and you continue to get a P0471 code, this would most likely indicate a failing exhaust pressure sensor, although a faulty PCM cannot be ruled out until the sensor has been replaced.

What does it mean?

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This generic powertrain/engine diagnostic code applies to all engines using variable nozzle turbochargers (gasoline or diesel), starting around 2005 on Ford trucks with 6.0L diesel engines, all Ford EcoBoost engines, and eventually leading to the Cummins 6.7L in 2007, the 3.0L in the Mercedes lineup in 2007, and more recently the Cummins 3.0L 6-cylinder in Nissan vans starting in 2015. This does not necessarily mean you won’t get this code in a VW or other brand.

This code is strictly concerned with the incoming signal from the exhaust pressure sensor not matching the intake manifold pressure or ambient air pressure during power-up. It is strictly an electrical circuit fault.

Code P0471 may also be present along with P0472. The main difference between these two codes is that P0472 is purely electrical while P0471 can result from a mechanical or electrical fault. It is generally recommended to start with P0473 (electrical) before moving on to P0471 (electrical/mechanical) next. This way, if the problem is electrical, there is a higher likelihood of repair by starting with the electrical system.

Troubleshooting steps may vary by manufacturer, gasoline or diesel, type of exhaust pressure sensor, and wire colors.

Related Exhaust Pressure Sensor Fault Codes:

• P0470 Exhaust Pressure Sensor “A” Circuit
• P0471 Exhaust Pressure Sensor “A” Circuit Range/Performance
• P0473 Exhaust Pressure Sensor “A” High Circuit
• P0474 Exhaust Pressure Sensor “A” Circuit Intermittent

Symptoms

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Symptoms of a P0472 engine code may include:

• Check Engine Light on
• Lack of power
• Unable to perform a manual regeneration – burn soot from the particulate filter. It looks like a catalytic converter but has temperature sensors and pressure sensor probes inserted in it.
• If it is unable to perform regeneration, it may eventually become a no-start condition.

Potential Causes

Typically, the causes for this code to set are:

• Open in the signal circuit between the exhaust pressure sensor and the PCM
• Open in the power supply circuit between the exhaust pressure sensor and the PCM
• Short to ground in the exhaust pressure sensor signal circuit
• Faulty exhaust pressure sensor – internal short to ground
• A Powertrain Control Module (PCM) may be faulty (very unlikely)

Diagnostic and Repair Procedures

---

A good starting point is always to check for a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogram to address this issue, and it’s worth checking before discovering you’ve taken a long/wrong path.

Next, locate the exhaust pressure sensor on your specific vehicle. Once located, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burns, or melted plastic. Separate the connectors and carefully inspect the terminals (the metal parts) inside the connectors. See if they appear corroded, burnt, or perhaps greenish compared to the normal metallic color you’re used to seeing. You can get electrical contact cleaner at any auto parts store if terminal cleaning is needed. If that’s not possible, find 91% rubbing alcohol and a soft plastic-bristled brush to clean them. Then let them air dry, get some dielectric silicone compound (same as used for bulb sockets and spark plug wires) and apply it where the terminals make contact.

If you have a scan tool, clear the diagnostic codes from memory and see if this code returns. If not, the connections were likely your problem.

If the code returns, we’ll need to test the sensor and its associated circuits. Typically, there are 3 wires to the exhaust pressure sensor.

Disconnect the harness going to the exhaust pressure sensor. With a digital voltmeter (DVOM), test the 5V supply circuit going to the sensor to ensure it has power (red wire to the 5V supply circuit, black wire to a good ground). If there are 12 volts at the sensor when there should be 5 volts, repair the wiring from the PCM to the sensor for a short to 12 volts, or possibly a faulty PCM.

If that’s okay, with a DVOM, check that the exhaust pressure sensor signal circuit is 5V (red wire to the sensor signal circuit, black wire to a good ground). If there is no 5 volts at the sensor, or if you see 12 volts at the sensor, repair the wiring from the PCM to the sensor, or again a faulty PCM.

If all tests have passed so far and you continue to get a P0472 code, this would most likely indicate a failing exhaust pressure sensor, although a faulty PCM cannot be ruled out until the sensor has been replaced.

What does it mean?

This generic powertrain/engine diagnostic code applies to all engines using variable nozzle turbochargers (gasoline or diesel), starting around 2005 on Ford trucks with 6.0L diesel engines, all Ford EcoBoost engines, and eventually leading to the Cummins 6.7L in 2007, the 3.0L in the Mercedes range in 2007, and more recently the Cummins 3.0L 6-cylinder in Nissan vans starting in 2015. This does not necessarily mean you won’t get this code in a VW or other brand.

This code is strictly concerned with the incoming signal from the exhaust pressure sensor not matching the intake manifold pressure or ambient air pressure during power-up. It is strictly an electrical circuit fault.

The P0471 code may also be present at the same time as P0473. The main difference between these two codes is that P0473 is purely electrical, while P0471 can be the result of a mechanical or electrical fault. It is generally recommended to start with P0473 (electrical) before moving on to P0471 (electrical/mechanical) next. This way, if the problem is electrical, there is a higher likelihood of repair by starting with the electrical system.

Troubleshooting steps may vary depending on the manufacturer, gasoline or diesel, the type of exhaust pressure sensor, and wire colors.

A typical exhaust pressure sensor:
Exhaust Pressure Sensor

Related Exhaust Pressure Sensor Fault Codes:

• P0470 Exhaust Pressure Sensor “A” Circuit
• P0471 Exhaust Pressure Sensor “A” Circuit Range/Performance
• P0472 Exhaust Pressure Sensor “A” Circuit Low
• P0474 Exhaust Pressure Sensor “A” Circuit Intermittent

Symptoms of an engine code P0473 may include:

1. Check Engine Light on
2. Lack of power
3. Unable to perform a manual regeneration – burn off soot from the particulate filter. It looks like a catalytic converter but has temperature sensors and pressure sensor probes inserted into it.
   If it is unable to perform regeneration, it may eventually lead to a no-start condition.

Potential Causes

Typically, the causes for this code to set are as follows:

1. Open in the ground circuit to the exhaust pressure sensor
2. Open in the signal circuit between the exhaust pressure sensor and the PCM
3. Short to voltage in the exhaust pressure sensor signal circuit
4. Faulty exhaust pressure sensor – internal short to voltage
5. A Powertrain Control Module (PCM) may be faulty (very unlikely)

Diagnostic and Repair Procedures

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A good starting point is always to search for a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogramming to address this issue, and it’s worth checking before discovering you’ve taken a long/wrong path.

Next, locate the exhaust pressure sensor on your specific vehicle. Once located, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burns, or melted plastic. Separate the connectors and carefully inspect the terminals (the metal parts) inside the connectors. See if they appear corroded, burnt, or perhaps greenish compared to the normal metallic color you’re probably used to seeing. You can get electrical contact cleaner at any auto parts store if terminal cleaning is needed. If that’s not possible, find 91% rubbing alcohol and a soft plastic-bristled brush to clean them. Then, let them air dry, get some dielectric silicone compound (the same kind used for bulb sockets and spark plug wires), and apply a small amount where the terminals make contact.

If you have a scan tool, clear the diagnostic codes from memory and see if this code returns. If it doesn’t, the connections were likely your problem.

If the code returns, we will need to test the sensor and its associated circuits. Typically, there are 3 wires to the exhaust pressure sensor.

Disconnect the harness going to the exhaust pressure sensor. With a digital voltmeter (DVOM), test the 5V supply circuit going to the sensor to ensure it has power (red wire to the 5V supply circuit, black wire to a good ground). If there are 12 volts at the sensor when there should be 5 volts, repair the wiring from the PCM to the sensor for a short to 12 volts, or possibly a faulty PCM.

If that’s okay, with a DVOM, check that the exhaust pressure sensor signal circuit is 5V (red wire to the sensor signal circuit, black wire to a good ground). If there is no 5 volts at the sensor, or if you see 12 volts at the sensor, repair the wiring from the PCM to the sensor, or again, a faulty PCM.

If that checks out, verify that the exhaust pressure sensor is properly grounded. Connect a test light to the positive 12V battery terminal (red terminal) and touch the other end of the test light to the ground circuit going to the exhaust pressure sensor circuit ground. If the test light does not illuminate, that would indicate a circuit problem. If it lights up, wiggle the wiring and go to the exhaust pressure sensor to see if the test light flickers, indicating an intermittent connection.

If all tests have passed so far and you continue to get a P0473 code, it would most likely indicate a failing exhaust pressure sensor, although a faulty PCM cannot be ruled out until the sensor has been replaced.

What Does It Mean?

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This generic powertrain/drivetrain diagnostic code applies to all engines using variable nozzle turbochargers (gasoline or diesel), starting around 2005 on Ford trucks with 6.0L diesel engines, all Ford EcoBoost engines, and eventually leading to the Cummins 6.7L in 2007, the 3.0L in the Mercedes lineup in 2007, and more recently the Cummins 3.0L 6-cylinder in Nissan vans starting in 2015. This does not necessarily mean you won’t get this code in a VW or other brand.

This code is strictly concerned with the incoming signal from the exhaust pressure sensor not matching the intake manifold pressure or ambient air pressure at various times during engine operation. This could be an electrical circuit fault or it could be mechanical.

Codes P0471, P0472, or P0473 may also be present along with P0474. The only difference between these codes is the duration of the problem and the type of electrical/mechanical issue encountered by the sensor/circuit/engine controller.

Troubleshooting steps may vary by manufacturer, gas or diesel, type of exhaust pressure sensor, and wire colors.

Related Exhaust Pressure Sensor Fault Codes:

P0470 Exhaust Pressure Sensor “A” Circuit
P0471 Exhaust Pressure Sensor “A” Circuit Range/Performance
P0472 Exhaust Pressure Sensor “A” Circuit Low
P0473 Exhaust Pressure Sensor “A” Circuit High

Symptoms

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Symptoms of a P0474 engine code may include:

Check Engine Light on
Lack of power
Unable to perform a manual regeneration – burn soot from the particulate filter. Looks like a catalytic converter but has temperature sensors and pressure sensor probes inserted in it.
If unable to perform regeneration, it may eventually become a no-start condition.

Potential Causes

Typically, the causes for this code to set are:

Blockage in the exhaust manifold tube to the pressure sensor
Exhaust Gas Recirculation (EGR) system / air intake / boost air leaks
Intermittent open in the exhaust pressure sensor ground circuit
Intermittent open in the signal circuit between the exhaust pressure sensor and the PCM
Intermittent short to voltage in the signal circuit to the exhaust pressure sensor
Exhaust Gas Pressure Sensor
A Powertrain Control Module (PCM) may be faulty (very unlikely)

Diagnostic and Repair Procedures

---

A good starting point is always to search for a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogramming to cover this issue, and it’s worth checking before finding out you’ve taken a long/wrong path.

Next, locate the exhaust pressure sensor on your specific vehicle. Once located, disconnect the tube connecting the sensor to the exhaust manifold. Try blowing through it. If you cannot, try running a small piece of wire through it to dislodge the carbon trapped inside, causing the fault code you are experiencing.

If the tube is clear and free, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burns, or melted plastic. Separate the connectors and carefully inspect the terminals (the metal parts) inside the connectors. See if they look corroded, burnt, or perhaps greenish compared to the normal metallic color you are probably used to seeing. You can get electrical contact cleaner at any auto parts store if terminal cleaning is needed. If that’s not possible, find 91% isopropyl alcohol and a soft plastic-bristled brush to clean them. Then, let them air dry, get some dielectric silicone compound (same as used for bulb sockets and spark plug wires) and apply a small amount where the terminals make contact.

Next, ensure the tube connecting the turbocharger to the intake manifold is not leaking. Visually inspect all tube connections around the turbocharger and intake manifold. Tighten all hose/band clamps.

If you have a scan tool, clear the diagnostic codes from memory and see if this code returns. If it does not, the connections were likely your problem.

If the code returns, we will need to test the sensor and its associated circuits. Typically, there are 3 wires to the exhaust pressure sensor. Disconnect the harness going to the exhaust pressure sensor. With a Digital Volt-Ohmmeter (DVOM), test the 5V supply circuit going to the sensor to ensure it is powered (red lead to the 5V supply circuit, black lead to a good ground). If there are 12 volts at the sensor when there should be 5 volts, repair the wiring from the PCM to the sensor for a short to 12 volts, or possibly a faulty PCM.

If that’s okay, with a DVOM, check that the exhaust pressure sensor signal circuit is 5V (red lead to the sensor signal circuit, black lead to a good ground). If there is no 5 volts at the sensor, or if you see 12V at the sensor, repair the wiring between the PCM and the sensor, or again, a possible faulty PCM.

If that checks out, verify the exhaust pressure sensor ground is good. Connect a test light to the positive 12V battery terminal (red terminal) and touch the other end of the test light to the ground circuit going to the exhaust pressure sensor circuit ground. If the test light does not illuminate, that would indicate the circuit problem. If it lights up, wiggle the wire harness going to each terminal to see if the test light flickers, indicating an intermittent connection.

If all tests have passed so far and you continue to get a P0474 code, try wiggling the sensor wire harness while watching the scan tool to see if the code returns. If it does, this most likely indicates an intermittent connection in the harness. If it does not, this would most likely indicate a faulty exhaust pressure sensor, although a faulty PCM cannot be ruled out until the sensor has been replaced.

What does it mean?

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This generic powertrain/engine diagnostic code generally applies to diesel engines, including but not limited to certain Ford, Dodge, Mercedes, Nissan, and VW vehicles.

This code may also apply to trucks equipped with diesel engines and dealer-installed exhaust brakes.

A valve is placed in the exhaust stream after the exhaust manifold to generate heat in the form of backpressure in the exhaust. This heat and/or backpressure can be used to assist with cold starts. It can also be used to oppose cylinder pressure from the engine cylinders to the exhaust, thereby slowing the engine and the vehicle with it. This is particularly useful during towing operations.

This code strictly pertains to the exhaust pressure control solenoid output circuit. This code is considered an electrical circuit fault only.

Troubleshooting steps may vary depending on the manufacturer, type of exhaust backpressure control, and the color of the control solenoid wires.

Symptoms

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Symptoms of a P0475 engine code may include:

    Malfunction Indicator Light (MIL) illuminated
    Lack of power
    Absence of engine braking
    Longer than normal cold engine warm-up time

Potential Causes

Typically, the causes for this code to set are as follows:

    Short to power in the supply circuit between the exhaust pressure control solenoid and the PCM (Powertrain Control Module)
    Open in the supply circuit between the exhaust pressure control solenoid and the PCM
    Short to ground in the exhaust pressure control solenoid supply circuit
    Faulty exhaust pressure control solenoid
    Possibly a failed PCM (highly unlikely)

Diagnostic and Repair Procedures

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A good starting point is always to search for a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogramming to address this issue, and it’s worth checking before discovering you’ve taken a long/wrong path.

Next, locate the exhaust pressure control solenoid on your specific vehicle. Once located, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burns, or melted plastic. Separate the connectors and carefully inspect the terminals (the metal parts) inside the connectors. See if they appear corroded, burned, or perhaps greenish compared to the normal metal color you’re used to seeing. You can get electrical contact cleaner at any auto parts store if terminal cleaning is needed. If that’s not possible, find 91% rubbing alcohol and a light plastic-bristled brush to clean them. Then let them air dry, get some dielectric silicone compound (same as used for light bulb sockets and spark plug wires), and apply it where the terminals make contact.

If you have a scan tool, clear the diagnostic codes from memory and see if this code returns. If not, the connections were likely your problem.

If the code returns, we’ll need to test the solenoid and its associated circuits. Typically, there are 2 wires to the exhaust pressure control solenoid. First, disconnect the wiring harness from the exhaust pressure control solenoid. With a digital volt-ohm meter (DVOM), connect one meter lead to one terminal of the solenoid. Connect the remaining meter lead to the other terminal of the solenoid. It should not be open or shorted. Check the resistance specifications for your specific vehicle. If the solenoid is open or shorted (infinite resistance or no resistance/0 ohms), replace the solenoid.

If that’s OK, with a DVOM, check that the exhaust pressure control solenoid supply circuit has 12V (red lead to the solenoid supply circuit, black lead to a good ground). Make sure the ignition is on. If there’s no 12 volts at the solenoid, or if there’s 12 volts when the ignition is off, repair the wiring from the PCM or relay to the solenoid, or possibly a faulty PCM.

If that’s fine, check that the exhaust pressure control solenoid is properly grounded. Connect a test light to the positive 12V battery terminal (red terminal) and touch the other end of the test light to the ground circuit going to the exhaust pressure control solenoid circuit ground. If the test light does not illuminate, that would indicate a circuit problem. If it lights up, wiggle the wiring harness going to each sensor to see if the test light flickers, indicating an intermittent connection.

If all tests have passed so far and you continue to get a P0475 code, it would most likely indicate a failing exhaust pressure control solenoid, although a faulty PCM cannot be ruled out until the solenoid has been replaced.

Understanding Error Code P0476: Exhaust Backpressure Valve Circuit Malfunction

Introduction

• What does the P0476 code mean? (General definition: problem with the incoming signal from the exhaust pressure sensor not matching expected values).
• This is a generic powertrain/engine diagnostic code, generally applicable to diesel engines (with examples of brands like Ford, Dodge, Mercedes, Nissan, and VW).
• May also apply to diesel trucks equipped with dealer-installed exhaust brakes.
• Function of the exhaust backpressure valve:
  • Generate heat (backpressure) in the exhaust after the manifold.
  • Used to facilitate cold starts.
  • Used for engine braking (slowing the vehicle, useful for towing).
• The P0476 code specifically concerns an incorrect signal from the exhaust pressure sensor relative to the intake manifold pressure, ambient pressure, or pre-programmed values during normal driving.
• The cause can be a mechanical or electrical circuit fault, varying depending on the vehicle manufacturer.
• Troubleshooting steps may vary by manufacturer, type of backpressure control, and color coding of the control solenoid wires.

Possible Symptoms of Code P0476

• List of associated symptoms:
  • Malfunction Indicator Lamp (MIL) illuminated
  • Lack of power
  • Absence of engine braking
  • Cold engine warm-up time longer than normal

Potential Causes of Code P0476

• List of possible causes:
  • Stuck exhaust backpressure valve
  • Turbocharger deflector potentially blocked, damaged, or misadjusted
  • Restriction or leak in the exhaust system
  • Faulty exhaust gas pressure sensor
  • PCM (Powertrain Control Module) failure (highly unlikely)

P0476 Diagnostic and Repair Procedures

• Essential preliminary step: Search for a Technical Service Bulletin (TSB) specific to your vehicle (make, model, year). The manufacturer may have a software update (PCM flash/reprogramming) to resolve this issue.
• Checking for exhaust leaks:
  • Listen carefully for abnormal exhaust noises at the manifolds and pipes.
  • Look for the presence of black soot indicating a leak.
  • If a leak is found, repair it first.
• Inspection of the exhaust pressure sensor, connectors, and wiring:
  • Locate the sensor on your vehicle.
  • Visually inspect the connectors and wiring for chafing, cuts, bare wires, burns, or melted plastic.
  • Separate the connectors and carefully examine the metal terminals inside for corrosion, burning, or abnormal discoloration (greenish).
  • Clean the terminals if necessary with electrical contact cleaner. If unavailable, use 91% isopropyl alcohol and a soft-bristled plastic brush.
  • Let it air dry, then apply a dielectric silicone compound (like that used for bulb sockets and spark plug wires) where the terminals make contact.
• Checking the sensing tube (if equipped):
  • If your vehicle is equipped, remove the tube connecting the exhaust backpressure sensor to the exhaust manifold.
  • Try to blow through it. An obstruction is a possible cause of the code.
• Clearing codes and testing:
  • If you have a scan tool, clear the diagnostic codes from the memory and see if the P0476 code returns. If not, the problem was likely related to connections.
• Checking turbocharger operation (if applicable):
  • If you have a scan tool capable of reading boost pressure (or intake manifold pressure).
  • Note the pressure with the ignition on, engine off.
  • Start the engine and, under safe driving conditions, briefly accelerate to full throttle (without exceeding 2500-3000 RPM).
  • You should observe a pressure change of at least 18 PSI (may vary by manufacturer and vehicle year).
  • If boost pressure is insufficient, suspect a faulty/misadjusted/stuck wastegate, an exhaust restriction, or a potentially faulty turbocharger.
• Testing the exhaust pressure sensor and its circuits:
  • Generally, the sensor has 3 wires.
  • Disconnect the harness going to the exhaust pressure sensor.
  • 5V Power Supply Test: With a digital voltmeter (DVOM), test the 5V supply circuit going to the sensor (red lead on the 5V supply wire, black lead to a good ground). If you measure 12V instead of 5V, repair the wiring between the PCM and the sensor for a short to 12V, or suspect a faulty PCM.
  • Signal Circuit Test: With a DVOM, check the voltage on the sensor’s signal circuit (red lead on the sensor signal wire, black lead to a good ground). If you do not measure 5V or if you measure 12V, repair the wiring between the PCM and the sensor, or suspect a faulty PCM.
  • Sensor Ground Test: Verify that the exhaust pressure sensor is properly grounded. Connect a test light to the positive battery terminal (red terminal) and touch the other end of the light to the ground circuit going to the sensor circuit ground. If the light does not illuminate, there is a ground circuit problem. If it illuminates, wiggle the wire harness going to the sensor to see if the light flickers, indicating an intermittent connection.
• Conclusion: If all previous tests are successful and the P0476 code persists, the exhaust pressure sensor is very likely faulty. However, a PCM failure cannot be ruled out until the sensor has been replaced.

What does it mean?

This generic powertrain/engine diagnostic code generally applies to diesel engines, including but not limited to certain Ford, Dodge, Mercedes, Nissan, and VW vehicles.

This code may also apply to trucks equipped with diesel engines and dealer-installed exhaust brakes.
A valve is placed in the exhaust stream after the exhaust manifold to generate heat in the form of backpressure in the exhaust. This heat and/or backpressure can be used to assist with cold starts. It may also be used to oppose cylinder pressure from the engine cylinders to the exhaust, thereby slowing the engine and the vehicle with it. This is particularly useful during towing operations.

This code is strictly concerned with the incoming signal from the exhaust pressure sensor that does not match the intake manifold pressure or ambient air pressure during normal driving. It could be a mechanical or electrical circuit fault, depending on the vehicle manufacturer.

Troubleshooting steps may vary by manufacturer, type of exhaust backpressure control, and the color of the control solenoid wires.

Symptoms

Symptoms of a P0477 engine code may include:

Malfunction Indicator Lamp (MIL) illuminated
Lack of power
Absence of engine braking
Longer than normal cold engine warm-up time

Potential Causes

Typically, the causes for this code to set are as follows:

Short to power in the supply circuit between the exhaust pressure control solenoid and the PCM (Powertrain Control Module)
Open in the supply circuit between the exhaust pressure control solenoid and the PCM
Short to ground in the exhaust pressure control solenoid supply circuit
Faulty exhaust pressure control relay
Faulty exhaust pressure control solenoid
Possibly a failed PCM (highly unlikely)

Diagnostic and Repair Procedures

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A good starting point is always to search for a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogramming to address this issue, and it’s worth checking before discovering you’ve taken a long/wrong path. PCM = Powertrain Control Module.

Next, locate the exhaust pressure control solenoid on your specific vehicle. Once located, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burns, or melted plastic. Separate the connectors and carefully inspect the terminals (the metal parts) inside the connectors. See if they appear corroded, burnt, or perhaps greenish compared to the normal metal color you’re used to seeing. You can get electrical contact cleaner at any auto parts store if terminal cleaning is needed. If that’s not possible, find 91% rubbing alcohol and a light plastic-bristled brush to clean them. Then, let them air dry, get some dielectric silicone compound (the same used for light bulb sockets and spark plug wires), and apply it where the terminals make contact.

If you have a scan tool, clear the diagnostic codes from memory and see if this code returns. If not, the connections were likely your problem.

If the code returns, locate the relay that operates the exhaust pressure control solenoid. This relay may also be called an exhaust brake or engine brake relay. Once located, swap it with an identical relay in the relay/fuse box that you know is working. Clear the codes and see if this code returns. If not, the relay was likely your problem.

If the code returns, we’ll need to test the solenoid and its associated circuits. Typically, there are 2 wires to the exhaust pressure control solenoid. First, disconnect the wiring harness from the exhaust pressure control solenoid. With a digital volt-ohm meter (DVOM), connect one meter lead to one terminal of the solenoid. Connect the remaining meter lead to the other terminal of the solenoid. It should not be open or shorted. Check the resistance specifications for your specific vehicle. If the solenoid is open or shorted (infinite resistance or no resistance/0 ohms), replace the solenoid.

If that’s okay, with a DVOM, check that the exhaust pressure control solenoid supply circuit has 12V (red lead to the solenoid supply circuit, black lead to a good ground). Make sure the ignition is on. If there is no 12 volts at the solenoid, or if there is 12 volts when the ignition is off, repair the wiring from the PCM or relay to the solenoid, or possibly a faulty PCM.

If that’s okay, check that the exhaust pressure control solenoid is properly grounded. Connect a test light to the positive 12V battery terminal (red terminal) and touch the other end of the test light to the ground circuit going to the exhaust pressure control solenoid circuit ground. If the test light does not illuminate, that would indicate a circuit problem. If it lights up, wiggle the wiring harness going in each direction