Diesel Trouble Codes

P0606 — Control Module Processor Performance (5.9 Cummins 24-Valve (VP44))

P0606 on the 1998.5–2002 Dodge Ram 2500/3500 5.9L Cummins 24-valve (VP44) means the Powertrain Control Module (PCM/ECU) has detected an internal processor…

Updated September 2, 2026

What it means

The PCM’s internal processor self-test has failed, indicating the control module may not be operating correctly. Generic definition: the PCM has detected an internal fault in its processor or its self-test routine, indicating the control module may not be operating correctly.1

Most likely causes

  1. Internal PCM processor fault / failed self-test — The PCM reports its own processor is not performing as expected. This is the generic definition for P0606 on this platform.1
  2. Corrupted or unstable PCM power/ground supply causing processor errors — Intermittent voltage drop or poor ground can make the PCM’s processor report a self-test failure. Diagnose power and ground integrity to the PCM before condemning the module.1
  3. Internal PCM hardware failure — A failing PCM can set P0606 when its internal circuitry degrades. Related PCM internal faults on this platform are described for P0602 programming error and P0605 ROM error.23

How to diagnose

  1. Verify the code is present and active with a scan tool; record freeze-frame data.
  2. Inspect PCM connectors for corrosion, bent pins, and secure seating; check for moisture intrusion.
  3. Check PCM power feeds and grounds for correct voltage and low resistance; load-test circuits.
  4. Clear codes and perform a PCM self-test/relearn drive cycle; confirm P0606 returns.
  5. If code returns with clean power/ground and connections, the PCM internal processor fault is indicated.
  6. Compare with related PCM internal codes P0602 and P0605 if present.
  7. Do not replace the VP44, lift pump, APPS, or sensors to address P0606; those systems are unrelated to a processor self-test failure per platform facts.
  8. If PCM replacement is required, ensure correct part number and proper programming for the 1998.5–2002 5.9L Cummins 24-valve.
  9. After repair, verify no codes return and engine runs normally.

Parts and tools you may need

Rough cost and difficulty

Diagnostic time is typically 0.5–1.0 hr. PCM replacement and programming can be several hundred to over a thousand dollars depending on part source and labor. Costs vary by region and shop.

When to see a pro

If P0606 persists after verifying power, ground, and connections, have the PCM tested or replaced by a qualified diesel technician. PCM programming must match the 1998.5–2002 5.9L Cummins 24-valve calibration. Do not attempt high-pressure fuel system or PCM internal repairs yourself.

Sources

  1. Curated DTC seed — 5.9 Cummins 24-Valve (VP44) (curated) ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — 5.9 Cummins 24-Valve (VP44) (curated) ↩︎

  3. Curated DTC seed — 5.9 Cummins 24-Valve (VP44) (curated) ↩︎