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 October 15, 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.

Specs and test values

CheckNormal readingWhen to measureSource
Battery and charging voltage12.6–12.7 V at rest when fully charged; about 13.5 V runningEngine off, then running with loads onDieselHub

Parts and tools you may need

Tools you’ll need

Rough cost and difficulty

Likely repairPartsShop laborWho usually does it
Wiring or connector repair$10–$1001–4 hrsDIY with tools and a manual
Battery or charging-system repair$150–$5000.5–2 hrsEasy DIY
ECM/PCM replacement (programmed)$600–$2,0001–3 hrsShop

Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

If the PCM is suspected failed, have it tested by a qualified diesel shop. Do not attempt high-pressure oil 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.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources

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

  2. NHTSA owner report 10222074 ↩︎

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

Repair videos: P0603 on the 7.3 Power Stroke

Third-party videos, not ours — picked for this engine. Confirm anything against the factory service information for your truck.

What Is The P0603 Code On A 7.3 Powerstroke? How To Fix It? — Auto Almanac · 28K views

7.3l Powerstroke rough running, cuts out, etc. The fix! — Pro Diesel Repair · 165K views