SPN 3510 FMI 4 — Sensor Supply Voltage 1 Below Normal
Supply 1 low voltage is resolved by isolating the shorted branch or sensor. Bank-specific cascades where only Supply 1 family fails while Supply 2 remains healthy is the most documented pattern on this fault class.
Fault Overview
SPN 3510 FMI 4 indicates sensor supply bank 1 voltage is below the minimum threshold. A shorted sensor on Supply 1, harness short to ground on that bank, and a failed supply driver are the primary causes. Bank-based isolation reduces unnecessary parts replacement on the healthy supply bank.
Engine & Platform Coverage
Symptoms
- •Multiple Supply 1 sensor codes active simultaneously
- •Supply 1 voltage collapsed or below OEM reference
- •Supply 2 remains healthy
- •Bank-specific sensor cascade
- •Multiple low-voltage codes on Supply 1 family only
Possible Causes
- 1.Shorted sensor on Supply 1 bank collapsing the reference
- 2.Harness short to ground on Supply 1 branch
- 3.Failed ECM supply driver for bank 1 — less common
- 4.Moisture intrusion at a Supply 1 branch connector
- 5.Chafed harness on Supply 1 routing
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
5 steps locked behind Technician Mode- 1Single Action Gate — Measure Supply 1: Measure Supply 1 voltage at the ECM reference output and at a known Supply 1 sensor. Key-on engine off. Supply 1 should be near OEM reference — typically 5V. A collapsed or low reading confirms the bank is loaded down.
- 2Binary Decision Gate — Branch Isolation by Group: Disconnect Supply 1 sensors by group — one branch at a time. Recheck Supply 1 voltage after each disconnection. Recovery of Supply 1 voltage after disconnecting one sensor or branch identifies the offender.
- 3Override Manager — Confirm Supply 2 Remains Healthy: Verify Supply 2 voltage is normal throughout the Supply 1 isolation process. If Supply 2 is also affected, the fault may be at the ECM supply output rather than a bank-specific branch.
- 4Safety Interceptor — Repair Shorted Sensor or Harness: Repair the identified shorted sensor or harness branch. Confirm Supply 1 voltage recovers to OEM specification after repair and before reconnecting all other loads.
- 5Resume Point — ECM Only If Bus Stays Dead With All Loads Removed: Proceed to ECM diagnosis only if Supply 1 remains collapsed with all sensor loads removed and power/grounds are confirmed good. This confirms the ECM supply driver is the source.
- 6Verification Loop — Post-Repair Supply Confirmation: After repair, verify Supply 1 is within OEM specification. Confirm all related sensor codes clear. Monitor for return of Supply 1 low conditions.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
2 steps locked- 1Repair shorted sensor at identified Supply 1 branch.
- 2Repair harness short to ground at identified location.
- 3Replace ECM only if Supply 1 remains collapsed with all loads removed and power/grounds are perfect.
- 4Verify Supply 2 remains healthy throughout repair process.
Unlock full diagnostic steps, DVOM tests, and repair procedures.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
Start Diagnosing This Fault Now
AI Diesel Tech walks you through every evidence gate in the correct order. Choose the plan that fits your shop.
Related Resources
Related Fault Codes
Related Systems
Related Fault Codes
Related Sensor Locations
Common Symptoms
Related Articles
AI Diesel Tech — The Technician's Diagnostic Engine
AI Diesel Tech diagnostic logic is built by an ASE Certified Diesel Technician and engineered for professional shop use. Trusted by technicians nationwide — used in shops, fleets, and training programs.
Summary
SPN 3510 FMI 4 is a bank-based isolation diagnosis. Supply 1 low voltage requires measuring the bank, disconnecting sensors by group, and repairing the shorted branch before any ECM replacement.