DPF Regeneration Fuel Quantity / Post-Injection Adaptation
Regen fuel quantity faults are diagnosed by correlating commanded quantity with temperature response and injector performance before aftertreatment component replacement.
Fault Overview
Issues related to the quantity of fuel used for in-cylinder post-injection or HC dosing during regen, including adaptation limits and quantity rationality faults. Quantity adaptation faults often point back to uneven injectors or pressure control problems rather than the aftertreatment hardware itself.
Engine & Platform Coverage
Symptoms
- •Regen fuel quantity
- •Post injection quantity
- •HC dosing adaptation
- •Regen fuel too high low
- •Post injection fault
Possible Causes
- 1.Injector contribution imbalance affecting post-injection
- 2.Fuel pressure instability
- 3.Adaptation limits reached
- 4.Wiring or driver issues on the dosing circuit
- 5.Temperature feedback errors causing quantity over- or under-command
- 6.Software calibration problems
Wiring & Circuit Notes
Inspect post-injection or HC doser driver circuits for voltage drop and integrity under the high-duty conditions of regen.
DVOM Specs & Sensor Tests
Commanded post-injection or HC quantity during regen. Rail pressure stability. DOC temperature response to the commanded quantity. Injector contribution data. Adaptation status if available.
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 — Monitor Commanded Regen Fuel Quantity and Rail Pressure During Forced Regen: Monitor commanded regen fuel quantity and rail pressure during a forced regen. Quantity adaptation faults often point back to uneven injectors or pressure control problems.
- 2Step 2 — Observe DOC Temperature Response: Observe DOC temperature response to the commanded quantity. Correct quantity with poor temperature response confirms a DOC or leak issue.
- 3Step 3 — Check Injector Contribution/Balance: Check injector contribution/balance. Uneven injectors affect post-injection delivery and adaptation.
- 4Step 4 — Verify Dosing Circuit Voltage and Current: Verify dosing circuit voltage and current. Inspect post-injection or HC doser driver circuits for voltage drop under regen conditions.
- 5Step 5 — Evaluate Temperature Sensor Feedback: Evaluate temperature sensor feedback. Errors in temperature feedback cause quantity over- or under-command.
- 6Step 6 — Correct Combustion or Pressure Issues That Force Abnormal Quantity: Correct combustion or pressure issues that force abnormal quantity.
- 7Step 7 — Retest Quantity and Light-Off After Repairs: Retest quantity and light-off after repairs to confirm the regen system is operating within calibration.
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
Injector service $300–2,000+; rail pressure control repair $200–800; circuit repair $100–300; temperature sensor service $120–400; software update if applicable.
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Summary
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