Injector Cylinders 3–6 Voltage Above / Below Normal Matrix
Voltage faults on injector circuits 3–6 are diagnosed by state measurement and multi-cylinder resistance comparison before parts replacement.
Fault Overview
Covers FMI 3 (voltage above normal) and FMI 4 (voltage below normal) conditions on injector circuits for cylinders 3–6. These indicate control circuit voltage out of expected range, often open, short-to-power, or short-to-ground conditions depending on driver design.
Engine & Platform Coverage
Symptoms
- •Injector voltage high
- •Injector voltage low
- •Cylinder 3–6 circuit voltage fault
- •Injector driver voltage fault
Possible Causes
- 1.Open control wire (high voltage on some drivers)
- 2.Short to power or ground
- 3.High-resistance connection
- 4.Failed driver
- 5.Oil-contaminated connector affecting voltage
Wiring & Circuit Notes
Full path inspection from ECM to each injector connector for the affected cylinders. Focus on pass-through and under-cover sections. Voltage codes frequently accompany or precede current codes when connectors degrade. Oil intrusion changes voltage readings before a full open or short develops.
DVOM Specs & Sensor Tests
Voltage on the control circuit in commanded and non-commanded states. Resistance of the coil. Voltage drop under actuation if measurable. Compare all cylinders 3–6 to each other and to specification.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
6 steps locked behind Technician Mode- 1Step 1 — Identify Affected Cylinders and FMI Type: Identify affected cylinder(s) and FMI type. FMI 3 (high voltage) and FMI 4 (low voltage) have different root causes depending on driver design.
- 2Step 2 — Measure Voltage on Control Circuit in Both States: Measure voltage on the control circuit in commanded and non-commanded states. Compare to expected values for the driver type.
- 3Step 3 — Measure Coil Resistance: Measure coil resistance on all affected cylinders and compare to specification and to each other.
- 4Step 4 — Continuity and Short Tests: Perform continuity and short tests on the signal wire from the injector connector to the ECM.
- 5Step 5 — Inspect Connectors for Oil and Pin Condition: Inspect connectors for oil and pin condition. Voltage codes frequently accompany or precede current codes when connectors degrade.
- 6Step 6 — Compare Readings Across Cylinders 3–6: Compare readings across all affected cylinders. A shared pattern points to a common power, ground, or harness issue.
- 7Step 7 — Isolate by Disconnection or Swap: Isolate by disconnection or swap if practical to confirm individual vs shared fault.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
Typical Repair Costs
Harness or connector repair $100–300; injector if internal fault confirmed $300–700; driver evaluation last. Total $120–700 per circuit.
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.
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AI Diesel Tech — The Technician's Diagnostic Engine
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Summary
Use the AI Diesel Tech diagnostic engine to run this code through a structured, evidence-gated sequence and get a confirmed root cause before any parts are replaced.