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P0602 — Control Module Programming Error

Moderate

Quick answer

P0602 means the computer believes its programming is incomplete or corrupted. First move: common after interrupted software updates or battery problems during programming — a dealer/shop reflash is often the cure, not a new module.

What it means

P0602 reports that the computer believes its programming is incomplete or corrupted.

Internal-module codes sound terminal — "the computer is dying!" — but the module itself is the LAST suspect, not the first. Computers fail their self-tests for external reasons constantly: low voltage during cranking, a battery that was disconnected, corroded grounds, water in a connector, or an interrupted software update.

Like every code on this site, the diagnosis below runs cheapest-first — the order exists because the cheap causes really are the common ones.

Common causes

Ordered from most to least likely.

  1. 1.

    See the diagnosis steps

    This family shares its suspect list; the steps below walk it in order of cost and likelihood.

  2. 2.

    Wiring or connector damage

    The universal suspect for any circuit-flavored code.

  3. 3.

    The component named by the code

    Condemned by measurement, never by guess.

How to diagnose it, step by step

Cheapest and most likely checks first.

  1. 1 Establish the power story

    Was the battery recently dead, disconnected, jumped, or replaced? Did this appear after another repair? Power interruptions explain a large share of these codes — especially KAM errors, where it's the expected behavior.

  2. 2 Test voltage and grounds

    Battery health, charging voltage, and the main grounds — a computer browning out during cranking will fail self-tests through no fault of its own.

  3. 3 Inspect the ECM physically

    Find the module, check its connectors for corrosion or water staining, and its location for evidence of leaks (cowl drains clogging above an ECM is a known pattern on several platforms).

  4. 4 Clear and observe

    With power verified, clear the code and drive several days. A code that doesn't return was a transient. One that returns with clean power moves the conversation to reflashing (where supported) and finally module replacement — which usually requires programming to your VIN.

Parts & tools you may need

  • OBD-II scanner (code reader with freeze frame / live data)
  • Digital multimeter
  • Replacement component per the diagnosis (sensor, relay, solenoid, pump as found)

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Frequently asked questions

What does P0602 mean in plain words?
The computer believes its programming is incomplete or corrupted. Common after interrupted software updates or battery problems during programming — a dealer/shop reflash is often the cure, not a new module.
How much is a new ECM?
Hundreds to over a thousand with programming — which is exactly why the diagnosis order above exists. Most of these codes resolve for the price of a battery service or a cleaned ground.
The code appeared right after my battery died. Coincidence?
No — that's the cause, especially for P0603 (keep-alive memory). The computer lost its learned values when power dropped. Clear it, drive normally while it relearns, and expect it not to return.