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1999 DODGE RAM VAN

5.9L V84WDAUTOMATICgas
Repairs0Labor505Torque3691Fluid9DTC645Battery0Maintenance0Recalls0
P1398moderate severityPowertrain

Misfire Adaptive Numerator At Limit

on 1999 Dodge Ram Van 5.9L V8 · 4WD

What this code means

The PCM misfire adaptive learning has reached its maximum correction limit. The system can no longer compensate for the detected misfire condition, indicating a persistent misfire problem that exceeds the adaptive range.

Symptoms

  • Check Engine Light
  • Noticeable engine misfire
  • Rough idle
  • Poor acceleration
  • Failed emissions test

Common causes

  • Worn spark plugs or ignition coils
  • Fuel injector malfunction
  • Low compression in one or more cylinders
  • Vacuum leak at specific cylinder
  • Crankshaft position sensor signal issue

Diagnostic steps

  1. Check for companion misfire codes (P0300-P0312) to identify affected cylinders
  2. Inspect spark plugs and ignition coils
  3. Perform fuel injector balance test
  4. Run compression test on suspected cylinders
  5. Check for vacuum leaks

Repair notes

Identify and repair the root cause misfire using companion codes; this code will clear once the misfire is resolved.

Other Powertrain codes on this vehicle

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