SPN 597 FMI 2 is a fault code that indicates a problem with the service brake switch signal on a Freightliner truck. The service brake switch is a device that sends a signal to the engine control module (ECM) when the driver applies or releases the service brake pedal. The ECM uses this signal to control various functions, such as the engine brake, the cruise control, the fan clutch, and the idle shutdown timer.
The fault code SPN 597 FMI 2 means that the ECM has detected an erratic, intermittent, or incorrect signal from the service brake switch. This could be caused by a number of reasons, such as:
- A faulty service brake switch or wiring
- A loose or corroded connector or terminal
- A short or open circuit in the service brake switch signal wire
- A mismatch between the service brake switch configuration and the actual switch installed
- A software glitch in the ECM or other modules
To troubleshoot this fault code, you need to follow these steps:
- Verify the fault code using a diagnostic tool, such as ServiceLink. Check if there are any other related codes, such as SPN 168 (Battery Voltage), SPN 625 (CAN Communication), or SPN 3597 (Low Pressure Pump Output Sensor). If there are, troubleshoot and repair them first.
- Check the service brake switch operation using the diagnostic tool or a multimeter. The service brake switch should have continuity when the pedal is applied and no continuity when the pedal is released. If the switch is not working properly, replace it.
- Check the wiring and connectors of the service brake switch circuit. Look for any signs of damage, corrosion, loose connections, or short or open circuits. Repair or replace any faulty components as needed.
- Check the configuration of the service brake switch using the diagnostic tool. Make sure that the switch type and source match the actual switch installed on the truck. If the configuration is incorrect, reprogram the ECM or other modules accordingly.
- Clear the fault code and test drive the truck. If the fault code does not reappear, the problem is solved. If the fault code reappears, contact the dealer or manufacturer for further assistance.
The following table summarizes the possible causes and solutions for the fault code SPN 597 FMI 2:
| Cause | Solution |
|---|---|
| Faulty service brake switch or wiring | Replace the switch or repair the wiring |
| Loose or corroded connector or terminal | Clean and tighten the connector or terminal |
| Short or open circuit in the service brake switch signal wire | Repair or replace the wire |
| Mismatch between the service brake switch configuration and the actual switch installed | Reprogram the ECM or other modules |
| Software glitch in the ECM or other modules | Update the software or replace the module |