SPN 5571: Aftertreatment 1 Diesel Exhaust Fluid Dosing Valve
POSTED IN pcodes
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Urgency and Driving Considerations**
If you encounter fault code SPN 5571, it indicates a serious issue with the high-pressure fuel system. Continuing to drive with this fault active risks severe engine damage. Upon receiving this code, safely pull over and shut off the engine as soon as possible. Have the vehicle towed to a dealer or diesel repair shop for diagnosis. Do not attempt to drive until the issue is resolved.
In our workshop, we’ve encountered fault code SPN 5571 quite frequently across various makes and models. Just last week, we had a Volvo truck in with this code, and the issue turned out to be a faulty fuel rail pressure limiting valve. We’ve also seen it on several Mercedes-Benz Actros trucks, where debris contamination in the valve was the culprit. It’s not just limited to European makes though – we’ve diagnosed SPN 5571 on Hino and Isuzu trucks as well. Interestingly, we haven’t had many American trucks come in with this specific fault code. From our experience, it seems to be more prevalent on European and Asian diesel engines. Regardless of the make, we always start with a thorough diagnostic process to pinpoint the exact cause, as there can be several factors at play, from wiring issues to high-pressure fuel pump failures.
Code Details
SPN 5571 is a generic fault code that applies to many makes and models of diesel engines, particularly PACCAR MX engines used in Peterbilt and Kenworth trucks. It indicates a problem with the fuel rail pressure control system:
- SPN 5571 FMI 0 – Fuel rail pressure limiting valve
- SPN 5571 FMI 7 – Fuel rail pressure limiting valve failed to close
- SPN 5571 FMI 16 – Fuel rail pressure limiting valve failed to open
The fuel rail pressure limiting valve controls maximum pressure in the common rail system. Located on the fuel rail, it opens to relieve excess pressure and protect injectors and other components.
Common Causes
- Faulty fuel rail pressure limiting valve
- Debris or contamination in the valve
- Wiring issues to the valve
- Malfunctioning fuel rail pressure sensor
- Excessive fuel pressure from failing high-pressure fuel pump
Diagnosis Steps
- Scan for all fault codes. SPN 5571 often occurs with other codes like SPN 157 FMI 18 (fuel rail pressure too high).
- Check wiring and connections to the pressure limiting valve and fuel rail pressure sensor. Repair as needed.
- Inspect the pressure limiting valve for contamination or damage. Clean or replace the valve.
- Measure actual fuel rail pressure with a gauge and compare to commanded pressure.
- If pressure is excessively high, perform further diagnosis on the high-pressure fuel pump and pressure regulator.
Repair Solutions
In most cases, replacing the fuel rail pressure limiting valve will resolve SPN 5571. The valve typically costs $250-300 USD (€225-275 EUR) plus 1-2 hours labor to replace.
If the valve is not faulty, further diagnosis and repair of the high-pressure fuel system may be required. This can be extensive, costing upwards of $3000 USD (€2700 EUR) if the pump or fuel injectors need replacement.
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Prevention
- Change fuel filters regularly, every 15,000 miles (24,000 km)
- Only use ultra-low sulfur diesel (ULSD) fuel from reputable suppliers
- Address leaks and contamination in the fuel system promptly
- Maintain the crankcase ventilation system to prevent oil in the intake
By understanding fault code SPN 5571, performing thorough diagnosis, and completing the necessary repairs, you can get your diesel engine running properly and reliably again. Always consult factory service information for specific troubleshooting procedures for your engine.
Frequently Asked Questions About SPN 5571
What does fault code SPN 5571 indicate?
SPN 5571 indicates a problem with the fuel rail pressure control system, specifically an issue with the fuel rail pressure limiting valve that controls maximum pressure in the common rail system.
What are the different Failure Mode Identifiers (FMI) for SPN 5571?
- SPN 5571 FMI 0 – Fuel rail pressure limiting valve
- SPN 5571 FMI 7 – Fuel rail pressure limiting valve failed to close
- SPN 5571 FMI 16 – Fuel rail pressure limiting valve failed to open
What engines commonly have this fault code?
SPN 5571 is a generic code that can occur on many diesel engines but is particularly common on PACCAR MX engines used in Peterbilt and Kenworth trucks.
What are the symptoms of SPN 5571?
Symptoms may include a lack of power, especially going uphill, as well as the engine running loudly. In some cases, the truck may not drive faster than a few mph.
Can I continue driving with SPN 5571?
No, you should not continue driving, as this risks severe engine damage. Safely pull over, shut off the engine, and have the vehicle towed for diagnosis and repair.
What causes SPN 5571?
Common causes include a faulty fuel rail pressure limiting valve, debris/contamination in the valve, wiring issues, a bad fuel rail pressure sensor, or excessive pressure from a failing high-pressure fuel pump.
What other codes may appear with SPN 5571?
SPN 5571 often appears with other codes like SPN 157 FMI 18 (fuel rail pressure too high) and SPN 1347 FMI 16.
How is SPN 5571 diagnosed?
Key diagnostic steps are:
- Scan for all fault codes
- Check wiring and connectors
- Inspect the pressure limiting valve
- Measure actual vs commanded fuel rail pressure
- Assess the high-pressure fuel pump if pressure is too high
What is the repair for SPN 5571?
In most cases, replacing the fuel rail pressure limiting valve will resolve the issue. If the valve is not faulty, further diagnosis and repair of the high-pressure fuel system may be needed.
Where is the fuel rail pressure limiting valve located?
The fuel rail pressure limiting valve is located on the fuel rail. It opens to relieve excess pressure and protect fuel system components like the injectors.
What is the part number for the pressure limiting valve?
The part number varies by engine but is commonly 1830662C91 for PACCAR MX engines.
How much does it cost to replace the pressure limiting valve?
The valve typically costs $250-300 USD (€225-275 EUR) plus 1-2 hours labor to replace.
What if replacing the valve doesn’t fix the problem?
If replacing the pressure limiting valve does not resolve SPN 5571, further diagnosis of the high-pressure fuel system is required. Repairs could be extensive, costing over $3000 USD (€2700 EUR) if the pump or injectors need replacement.
Can SPN 5571 be prevented?
Regular maintenance helps prevent SPN 5571:
- Change fuel filters every 15,000 miles (24,000 km)
- Use only ultra-low sulfur diesel from reputable suppliers
- Promptly fix any fuel leaks or contamination
- Maintain the crankcase ventilation system
What happens if SPN 5571 is not repaired?
Ignoring SPN 5571 and continuing to drive can result in major engine damage, as the fuel system will not be protected from excessive rail pressure.
Can I diagnose and repair SPN 5571 myself?
Diagnosing and repairing SPN 5571 requires advanced tools and knowledge. It is recommended to have the vehicle diagnosed and repaired by a qualified diesel technician.
What scan tools can read SPN 5571?
Most professional-grade diagnostic scan tools can read generic fault code SPN 5571. However, a manufacturer-specific scanner may be needed to access more detailed fault information and perform bi-directional tests.
Will disconnecting the batteries clear the code?
Disconnecting the batteries may temporarily clear SPN 5571 but will not fix the underlying cause. The code will reappear once the fault condition is again detected. Proper diagnosis and repair are needed.
Is SPN 5571 covered under warranty?
Warranty coverage for SPN 5571 depends on the specific warranty terms, vehicle age, and mileage. Check with your dealer to determine if repairs may be covered.
Where can I find more information about SPN 5571?
For more information specific to your engine, consult the manufacturer’s service information, repair manual, or diagnostic troubleshooting guide. Technical service bulletins (TSBs) may also be available detailing common causes and repairs for SPN 5571.
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