SPN 7138: EGR Position Sensor

Fault Code SPN 7138: What It Means and How to Fix It

Urgency and Severity

• SPN 7138 is a moderately severe fault code related to the Exhaust Gas Recirculation (EGR) system. While it's not typically necessary to stop driving immediately, it's best to diagnose and repair the issue promptly to prevent potential damage to the EGR valve or other components.
• Continuing to drive with an active SPN 7138 code can lead to reduced engine performance, increased emissions, and potentially costlier repairs if left unaddressed for an extended period.

Understanding SPN 7138

• SPN 7138 specifically indicates a problem with the EGR position sensor, which monitors the position and movement of the EGR valve. This sensor ensures the valve is opening and closing properly to regulate exhaust gas flow back into the engine.
• The code is manufacturer-specific and most commonly appears on medium and heavy-duty trucks equipped with MaxxForce engines, such as those found in International/Navistar vehicles.
• The EGR system helps reduce nitrogen oxide (NOx) emissions by recirculating a portion of the exhaust gases back into the engine. The EGR valve controls the flow of these gases, and the position sensor provides feedback to the ECM to ensure proper valve operation.

Common Causes

• A faulty or failing EGR position sensor is the most common cause of SPN 7138. The sensor may provide inaccurate readings or no signal at all due to wear, damage, or electrical issues.
• Wiring problems, such as damaged wires, loose connections, or corrosion, can also lead to SPN 7138 by disrupting the signal from the position sensor to the ECM.
• In some cases, a stuck or malfunctioning EGR valve can cause the position sensor to trigger the code if the valve is not responding as expected.

Diagnosis and Troubleshooting

1. Connect a diagnostic scan tool and check for any additional fault codes. If multiple codes are present, diagnose and repair them in the order specified by the manufacturer.
2. Visually inspect the wiring harness and connectors for the EGR position sensor. Look for any signs of damage, corrosion, or loose connections and repair as needed.
3. Using a digital multimeter, test the continuity and resistance of the position sensor circuit per the manufacturer's specifications. Replace the sensor if the readings are out of range.
4. If the wiring and sensor test okay, inspect the EGR valve for proper operation. Check for sticking, binding, or visible damage and replace the valve if necessary.

Repair Solutions

• In most cases, replacing the faulty EGR position sensor will resolve SPN 7138. This is a relatively straightforward repair that can often be done by a skilled DIYer with basic tools.
• If wiring issues are found, repair or replace the damaged wires or connectors as needed. Ensure all connections are clean, secure, and properly sealed against moisture.
• If the EGR valve is stuck or malfunctioning, it will need to be replaced. This is a more involved repair that may require special tools and is often best left to a professional mechanic.

Parts and Costs

• EGR position sensor: $100-$300 (€85-€255)
• EGR valve: $500-$1,000 (€425-€850)
• Labor costs for sensor replacement: $100-$200 (€85-€170)
• Labor costs for valve replacement: $400-$800 (€340-€680)

Prevention and Maintenance

• Regular inspection and cleaning of the EGR system can help prevent issues like SPN 7138. Check the EGR valve and passages for carbon buildup and clean as needed.
• Following the manufacturer's recommended service intervals for EGR system maintenance, typically every 50,000 to 100,000 miles (80,000 to 160,000 km), can also help prevent problems.

Related Issues

• SPN 2392 FMI 6 is another code related to the EGR position sensor and may appear alongside SPN 7138. This code indicates a specific range or performance issue with the sensor.
• Other EGR system codes, such as those related to the EGR valve or cooler, may also be present if the problem extends beyond just the position sensor.

By understanding the causes, diagnostics, and repairs associated with SPN 7138, vehicle owners and technicians can effectively address this fault code and keep the EGR system functioning properly for optimal engine performance and emissions control.

Frequently Asked Questions about SPN 7138 Fault Code

What is fault code SPN 7138?

SPN 7138 is a diagnostic trouble code that indicates a problem with the Exhaust Gas Recirculation (EGR) system, specifically the EGR position sensor. This code is triggered when the sensor readings are outside the expected range of performance.

What are the symptoms of SPN 7138?

Common symptoms include:

• Check engine light illuminated
• Reduced engine performance
• Rough idle or misfires
• Increased fuel consumption
• Failed emissions test

What causes SPN 7138?

The most common causes are:

• Faulty EGR position sensor
• Damaged wiring or loose connections to the sensor
• Stuck or malfunctioning EGR valve
• Carbon buildup in the EGR system passages

Is it safe to drive with SPN 7138?

While it’s not typically an emergency situation requiring immediate stoppage, it’s best to diagnose and repair SPN 7138 promptly. Continuing to drive with this code active can lead to reduced performance, increased emissions, and potentially costlier repairs if ignored.

What vehicles are prone to SPN 7138?

This code is most common on medium and heavy-duty trucks equipped with MaxxForce engines, such as International/Navistar vehicles. However, EGR position sensor issues can occur on any vehicle with an EGR system.

How do you diagnose SPN 7138?

Diagnosis involves these key steps:

1. Scan for additional codes and address them first if needed
2. Visually inspect wiring and connectors for damage
3. Test EGR position sensor circuit with a multimeter
4. Check EGR valve for proper operation

Can SPN 7138 cause the engine to derate?

Yes, if the EGR system is not functioning properly due to a position sensor issue, the engine may derate power to protect components and limit emissions. The severity of derate depends on the specific fault.

What is the EGR position sensor and what does it do?

The EGR position sensor monitors the position and movement of the EGR valve. It sends a signal to the engine control module (ECM) to ensure the valve is opening and closing properly to regulate exhaust gas flow.

How much does it cost to fix SPN 7138?

Repair costs depend on the root cause. Common estimates include:

• EGR position sensor replacement: $100-$300
• EGR valve replacement: $500-$1,000
• Labor costs vary but typically range from $100-$800

Can I replace the EGR position sensor myself?

Replacing just the sensor is a straightforward repair that many DIYers can complete with basic tools. However, if the valve or other components need service, it’s best left to a professional.

What other codes may appear with SPN 7138?

Related codes that may be triggered alongside SPN 7138 include:

• SPN 2392 FMI 6 (EGR position sensor performance)
• SPN 2393 FMI 2 (EGR position sensor circuit)
• SPN 8321 FMI 12 (VGT communication issue)

How often should the EGR system be serviced?

Most manufacturers recommend inspecting and cleaning the EGR system every 50,000 to 100,000 miles (80,000 to 160,000 km). Regular service can help prevent issues like SPN 7138.

Can a clogged EGR valve cause SPN 7138?

Yes, if the EGR valve becomes stuck due to carbon buildup or other debris, it can cause the position sensor to read out of range and trigger SPN 7138. Cleaning or replacing the valve may be necessary.

What does FMI mean in the fault code?

FMI stands for Failure Mode Indicator. It’s a number that provides more detail about the specific problem, such as a circuit issue, out of range reading, etc. SPN 7138 is often paired with FMI 6, indicating a performance problem.

What tools are needed to diagnose SPN 7138?

To properly diagnose this code, you’ll need:

• OBD-II scanner or diagnostic tool
• Digital multimeter
• Vehicle service manual for wiring diagrams and specifications

Can low coolant cause SPN 7138?

No, low coolant will not directly trigger SPN 7138. However, if the engine overheats due to low coolant, it can cause damage to various sensors and components, potentially leading to EGR system issues.

How does the EGR system affect emissions?

The EGR system helps reduce nitrogen oxide (NOx) emissions by recirculating a portion of the exhaust gases back into the engine. This lowers combustion temperatures and limits NOx formation. A malfunctioning EGR system can lead to increased emissions.

What should I do if SPN 7138 keeps coming back after repairs?

If the code persists after replacing the sensor or other components, there may be an underlying issue with the EGR system or engine. Further diagnosis by a professional technician is recommended to identify and resolve the root cause.

Can using the wrong oil cause EGR issues?

Using the incorrect oil viscosity or type for your engine can lead to increased carbon buildup and sludge, potentially clogging the EGR system over time. Always use the manufacturer-recommended oil to help prevent EGR problems.

What are the risks of deleting the EGR system?

While some vehicle owners may choose to delete the EGR system to avoid issues like SPN 7138, doing so is illegal and can lead to significant fines. Removing the EGR system also increases NOx emissions and can cause engine damage due to higher combustion temperatures. It is strongly advised against modifying or deleting any emissions control devices.