SPN 5435 – Aftertreatment 1 Diesel Exhaust Fluid Pump State

Understanding SPN 5435

SPN 5435 is a diagnostic trouble code (DTC) related to issues with the Diesel Exhaust Fluid (DEF) system. It typically indicates a "Non DEF flow situation" where the DEF pump speed is low. The exact description may vary by vehicle make and model.

This code is associated with the Selective Catalytic Reduction (SCR) system, which uses DEF fluid to reduce NOx emissions in diesel engines. When the DEF pump is not supplying adequate fluid to the SCR system, SPN 5435 may be triggered.

Symptoms

Common symptoms when SPN 5435 is active include:

• Illuminated MIL (Malfunction Indicator Lamp)
• Derate condition (reduced engine power)
• Increased NOx emissions
• Poor DEF consumption

In most cases, it is not recommended to continue driving extensively with SPN 5435 present. The root cause should be diagnosed and repaired promptly to avoid potential damage to the aftertreatment system.

Possible Causes

Some potential causes for SPN 5435 include:

• Faulty DEF pump
• Clogged DEF lines or injector
• Wiring issues with the DEF pump
• Low DEF fluid level
• Contaminated or degraded DEF fluid
• Malfunctioning DEF tank heater
• Faulty DEF tank level or temperature sensors

Diagnosis

To properly diagnose SPN 5435, follow these steps:

1. Retrieve all active fault codes and note freeze frame data
2. Check DEF fluid level and quality
3. Inspect DEF pump wiring and connectors for damage
4. Perform a DEF pump flow test
5. Check for restrictions in DEF lines and at injector
6. Verify operation of DEF tank heater
7. Test DEF tank level and temperature sensors

A scan tool with bi-directional controls is very helpful for testing the DEF pump and other components. Always refer to the OEM service information for specific diagnostic procedures.

Repairs and Costs

After identifying the root cause, perform the necessary repairs. Common fixes and estimated costs include:

• Replace DEF pump: $800-2000 (€680-1700)
• Clean/replace clogged DEF injector: $500-1500 (€425-1275)
• Repair damaged wiring: $100-300 (€85-255)
• Replace contaminated DEF fluid: $5-7/gallon ($1.32-1.85/liter)
• Replace faulty DEF tank heater: $200-600 (€170-510)
• Replace DEF level/temp sensors: $200-400 each (€170-340)

Labor rates are typically $100-175/hr (€90-160/hr) with most repairs taking 2-8 hours.

Prevention

To help prevent SPN 5435 issues:

• Maintain proper DEF levels with high-quality fluid
• Address any DEF leaks or engine issues promptly
• Allow for periodic SCR/DEF system maintenance
• Avoid excessive idling which can degrade DEF

Associated Codes

Other codes that may appear alongside SPN 5435 include:

• SPN 3031 – Aftertreatment 1 Outlet NOx Sensor
• SPN 5394 – Aftertreatment 1 DEF Dosing Valve
• SPN 5484 – Aftertreatment 1 DEF Tank Level

These often indicate related problems with the DEF system, NOx sensors, or SCR catalyst that should be addressed as well.

By understanding SPN 5435, performing thorough diagnosis, and completing the required repairs, technicians can resolve DEF system issues and restore proper emissions control. Proper maintenance of the DEF system is crucial for ensuring optimal engine performance and regulatory compliance.

Frequently Asked Questions about SPN 5435

What is SPN 5435?

SPN 5435 is a diagnostic trouble code (DTC) that indicates an issue with the Diesel Exhaust Fluid (DEF) pump. It typically points to a "DEF Pump Speed Low" condition where the pump is not operating at the expected speed.

What are the symptoms of SPN 5435?

Common symptoms when SPN 5435 is active include:

• Illuminated Malfunction Indicator Lamp (MIL)
• Derate condition with reduced engine power
• Increased NOx emissions
• Poor DEF consumption

Is it safe to drive with SPN 5435?

While it may be possible to continue driving for a short distance, it's best to diagnose and repair the underlying issue promptly. Ignoring SPN 5435 can lead to further damage to the aftertreatment system.

What systems are related to SPN 5435?

SPN 5435 is associated with the Selective Catalytic Reduction (SCR) system, which uses DEF fluid to reduce NOx emissions in diesel engines. The DEF pump supplies fluid to the SCR system.

What are common causes of SPN 5435?

Potential causes for SPN 5435 include:

• Faulty DEF pump
• Clogged DEF lines or injector
• Wiring issues with the DEF pump
• Low DEF fluid level
• Contaminated or degraded DEF fluid

How do you diagnose SPN 5435?

To diagnose SPN 5435:

1. Retrieve fault codes and freeze frame data
2. Check DEF level and quality
3. Inspect DEF pump wiring and connectors
4. Perform a DEF pump flow test
5. Check for restrictions in DEF lines and at injector

What repairs are needed for SPN 5435?

Common repairs for SPN 5435 are:

• Replacing the DEF pump
• Cleaning/replacing clogged DEF injector
• Repairing damaged wiring
• Replacing contaminated DEF fluid

What is the FMI associated with SPN 5435?

The most common Failure Mode Identifier (FMI) for SPN 5435 is FMI 7, which indicates a mechanical system not responding properly or out of adjustment.

Can low DEF level cause SPN 5435?

Yes, if the DEF tank runs empty, air can enter the system and the pump may not be able to prime and provide adequate flow, triggering SPN 5435.

Will a failed DEF pump always set SPN 5435?

A faulty DEF pump is a primary cause of SPN 5435, but it will not always set the code. The pump speed must drop below a certain threshold before the fault is triggered.

Can a clogged DEF injector set SPN 5435?

Yes, a restricted DEF injector creates excessive back pressure on the pump. This increased load can cause the pump speed to drop, setting SPN 5435.

Will contaminated DEF fluid set SPN 5435?

Contaminated or degraded DEF can clog the pump, lines, and injector, all of which could lead to SPN 5435. Always use high-quality DEF that meets ISO 22241 specifications.

Is SPN 5435 specific to certain engine makes?

SPN 5435 can appear on any vehicle using the J1939 protocol. However, the exact fault description may vary slightly between manufacturers.

What other codes may appear with SPN 5435?

Related codes that often appear with SPN 5435 include:

• SPN 3361 FMI 31 – DEF Dosing Unit Error
• SPN 3031 – DEF Tank Temperature Sensor issues
• SPN 1761 – DEF Tank Level Sensor issues

Can SPN 5435 cause engine damage?

SPN 5435 itself does not cause engine damage. However, the root cause, such as contaminated DEF fluid, could harm other components if not addressed promptly.

Will clearing SPN 5435 fix the problem?

No, simply clearing SPN 5435 without repairing the underlying issue will not solve the problem. The code will likely reappear until the root cause is diagnosed and corrected.

What is the urgency if SPN 5435 appears?

SPN 5435 should be diagnosed and repaired promptly to prevent escalation to more severe derate conditions. In cold weather, heater issues can prevent thawing, triggering additional faults.

How much does it cost to repair SPN 5435 issues?

Repair costs for SPN 5435 vary but typical estimates are:

• DEF pump: $800-2000 (€680-1700)
• DEF injector: $500-1500 (€425-1275)
• Wiring repairs: $100-300 (€85-255)

Can SPN 5435 cause a vehicle to shut down?

If SPN 5435 is not resolved promptly, it can escalate to more severe derate conditions and eventually lead to a vehicle speed limit or shutdown.

How can SPN 5435 be prevented?

To help prevent SPN 5435:

• Maintain proper DEF levels with quality fluid
• Address any DEF leaks or engine issues promptly
• Allow for periodic SCR system maintenance
• Avoid excessive idling which can degrade DEF

By understanding SPN 5435, its causes, symptoms, and diagnostic steps, technicians can efficiently troubleshoot and repair DEF pump issues to restore proper emissions control.