SPN 974 FMI 2 – Remote Accelerator Pedal Supply Voltage Out of Range Fault Code (Symptoms, Causes & Fix)
The SPN 974 FMI 2 fault code indicates that the remote accelerator pedal supply voltage is out of range. This diesel engine fault code suggests an issue with the electrical signal from the accelerator pedal position sensor to the ECM (Engine Control Module). When the ECM detects a voltage outside the expected range, it triggers this diagnostic trouble code.
What SPN 974 FMI 2 Means
The SPN 974 FMI 2 fault code specifically relates to the remote accelerator pedal's supply voltage being outside its normal operating range. This can occur if the voltage signal from the accelerator pedal position sensor is too high or too low, which the ECM interprets as a potential fault in the sensor circuit or related components.
Common Causes of This Fault Code
- Faulty accelerator pedal position sensor
- Damaged or corroded wiring harness
- Poor electrical connections at the pedal sensor
- Defective ECM or faulty ECM pin connections
- Voltage reference faults
Symptoms Drivers May Notice
When the SPN 974 FMI 2 fault code is active, drivers may experience symptoms such as erratic throttle response, reduced engine power, or unexpected acceleration behavior. In some cases, the engine may enter a derate mode to prevent further issues.
How Technicians Diagnose This Fault
Diagnosing the SPN 974 FMI 2 fault involves a systematic approach:
- Start with a visual inspection of the wiring harness for any visible damage or corrosion.
- Check the electrical connections at the accelerator pedal position sensor for tightness and corrosion.
- Use a multimeter to measure the supply voltage at the pedal sensor to ensure it is within specifications.
- Perform a continuity test on the wiring from the ECM to the pedal sensor.
- Use a diagnostic tool to monitor live data from the accelerator pedal position sensor to check for erratic readings.
Common Misdiagnosis
Technicians often make mistakes such as replacing the accelerator pedal assembly without verifying the wiring integrity or assuming ECM failure without performing proper voltage and continuity checks. Overlooking corroded connectors that can cause intermittent voltage issues is also a common error.
Can You Keep Driving?
While it may be possible to continue driving with the SPN 974 FMI 2 fault code active, it is not advisable. The issue can lead to unpredictable throttle response and potential safety concerns. Additionally, the engine may enter a derate mode, reducing power and performance.
Mechanic's Diagnostic Tip
Always verify the integrity of the wiring and connectors before replacing any components. Many issues related to the SPN 974 FMI 2 fault code stem from simple electrical problems that can be resolved without part replacement.
Frequently Asked Questions
- What tools are needed to diagnose SPN 974 FMI 2? A multimeter and a diagnostic scan tool are essential for checking voltage and continuity.
- Can a faulty ECM cause this fault code? Yes, a defective ECM or poor ECM pin connections can contribute to this fault.
- Is it safe to drive with this fault code? It is not recommended due to potential throttle response issues and safety concerns.
