SPN 1073 FMI 5 – Jake Brake Stage 2 Circuit Failed Open Fault Code (Symptoms, Causes & Fix)
The SPN 1073 FMI 5 fault code indicates an open circuit in the Jake Brake Stage 2 system of a diesel engine. This diagnostic trouble code is triggered when the Engine Control Module (ECM) detects a failure in the electrical circuit responsible for activating the second stage of the engine brake, commonly known as the Jake Brake. Understanding this diesel engine fault code is crucial for ensuring proper engine braking functionality.
What SPN 1073 FMI 5 Means
The SPN 1073 FMI 5 fault code specifically points to an electrical issue within the Jake Brake Stage 2 circuit. The ECM monitors the circuit for continuity and proper operation. When it detects an open circuit, it logs this fault code, indicating that the solenoid responsible for engaging the second stage of the Jake Brake is not receiving the necessary electrical signal to function.
Common Causes of This Fault Code
- Open circuit in the Jake Brake Stage 2 wiring
- Faulty Jake Brake solenoid
- Corroded or damaged connectors
- Faulty Engine Control Module (ECM) output
Symptoms Drivers May Notice
When the SPN 1073 FMI 5 fault code is active, drivers may notice a lack of engine braking power, particularly when the second stage of the Jake Brake is engaged. This can result in reduced braking efficiency, especially on downhill grades, leading to increased reliance on the service brakes.
How Technicians Diagnose This Fault
Technicians begin diagnosing the SPN 1073 FMI 5 fault code with a thorough visual inspection of the Jake Brake wiring harness, looking for signs of damage or corrosion. Using a multimeter, they check for continuity in the Jake Brake Stage 2 circuit to identify any open circuits. The Jake Brake solenoid is then inspected and tested for proper operation. Additionally, the ECM is checked for any additional fault codes that might indicate an ECM issue. Finally, technicians verify the power and ground supply to the Jake Brake solenoid to ensure it is receiving the correct voltage.
Common Misdiagnosis
A common misdiagnosis with the SPN 1073 FMI 5 fault code is replacing the Jake Brake solenoid without verifying the integrity of the circuit. Technicians may also mistakenly assume a mechanical failure without thoroughly checking the electrical connections. Overlooking corroded connectors as a potential cause is another frequent error.
Can You Keep Driving?
While the truck can continue to operate with the SPN 1073 FMI 5 fault code active, it is not advisable to ignore the issue. The lack of effective engine braking can lead to increased wear on the service brakes and potential safety concerns, particularly in hilly or mountainous terrain. Addressing the fault promptly is recommended to maintain optimal braking performance.
Mechanic's Diagnostic Tip
When troubleshooting the SPN 1073 FMI 5 fault code, always start with a thorough inspection of the wiring and connectors. Corrosion and damage are common culprits in electrical faults. Ensure all connections are clean and secure before considering component replacement.
Frequently Asked Questions
Q: Can a faulty ECM cause the SPN 1073 FMI 5 fault code?
A: Yes, a faulty ECM output can contribute to this fault code, but it is less common than wiring or solenoid issues.
Q: Is it safe to drive with a non-functional Jake Brake?
A: While it is possible to drive, it is not recommended due to reduced braking efficiency, especially in demanding driving conditions.
Q: How can I prevent this fault code from occurring?
A: Regular maintenance, including checking and cleaning electrical connections, can help prevent the SPN 1073 FMI 5 fault code from occurring.
