Diesel Trouble Codes

P0603 — Internal Control Module Keep Alive Memory Error (7.3 Power Stroke)

The PCM detected an internal fault or loss of data in its keep-alive memory, which stores learned adaptations and settings when the ignition is off. On the…

Updated September 2, 2026

What it means

The PCM detected an internal fault or loss of data in its keep-alive memory, which stores learned adaptations and settings when the ignition is off. On the 7.3L Power Stroke this is a PCM internal KAM/ROM error, very common on this platform, usually a PCM power/ground or a failing PCM, not an engine fault.11

Most likely causes

  1. PCM power/ground supply interruption or voltage drop causing KAM loss — Intermittent loss of battery voltage to the PCM keep-alive circuit can corrupt KAM. NHTSA reports of P0603 with total electrical loss, gauges full tilt, ABS light, no restart until batteries recharged point to power/ground issues.21
  2. Failing or internally faulty PCM — P0603 is a PCM internal KAM error; P0605 is the related ROM error. Both are described as PCM internal memory faults on the 7.3L Power Stroke.13
  3. Corrupted KAM due to repeated low-voltage events or battery disconnects — Keep-alive memory stores learned adaptations when ignition is off; loss of data is flagged as P0603.1

How to diagnose

  1. Verify battery condition and charging system voltage; inspect PCM power and ground circuits for corrosion, loose terminals, and voltage drop under load.
  2. Check for other electrical symptoms such as intermittent stalling, gauge sweep, ABS light, or total electrical loss reported with P0603.
  3. Inspect PCM connectors for moisture, corrosion, or pin damage; confirm keep-alive memory power feed is present with key off.
  4. Review freeze frame and related codes; P0603 often appears with other PCM memory codes such as P0605.
  5. If power/ground integrity is confirmed good and code returns after clearing, PCM internal failure is likely.

Parts and tools you may need

Rough cost and difficulty

Diagnostic time for electrical checks is typically 1–2 hours. PCM replacement or professional reprogramming is significantly higher; costs vary by source and labor.

When to see a pro

If the PCM is suspected failed, have it tested by a qualified diesel shop. Do not attempt high-pressure fuel or safety-critical repairs without proper training. PCM replacement/reprogramming requires professional equipment and calibration. If you experience sudden loss of all electrical systems, gauges full tilt, or no restart, seek immediate professional diagnosis.

Sources

  1. Curated DTC seed — 7.3 Power Stroke (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎

  2. NHTSA owner report 10222074 ↩︎

  3. Curated DTC seed — 7.3 Power Stroke (curated) ↩︎