Electrical and sensors

P0602 — Control Module Programming Error

Severity: medium Drive with care, to a shop

What P0602 means

The control module ran a self-test and found that its software or calibration data is corrupt, incomplete or fails the checksum. This often happens after a reflash, a module replacement or a power loss during programming. A healthy module verifies its stored data every time it wakes up.

Symptoms

  • No-start after a reflash
  • Check Engine light on
  • Several modules setting faults at once
  • Security or immobilizer light on
  • Rough running or odd transmission behavior
  • Symptoms vary with the affected internal function

Possible causes

  1. Interrupted programming (voltage drop or power loss)
  2. Corrupt flash file
  3. Wrong calibration or software for the vehicle
  4. Weak battery or low system voltage
  5. Poor power or ground supply to the module
  6. Failed internal memory in the module itself

How to diagnose

  1. Scan all modules and note which one sets P0602, plus freeze frame data
  2. Test the battery at rest and during cranking, and check charging voltage
  3. Check module power and grounds: fuses, relays, connectors, corrosion
  4. Find out whether a reflash or module swap was done and which software version is installed
  5. Compare the software and calibration with OEM data and technical bulletins
  6. Clear the code and see whether it returns
  7. If it returns, reprogram with the correct OEM software using a stable power supply
  8. Only then consider the module itself faulty

Common fixes

  • Repair power and ground supply problems and replace a weak battery
  • Reflash the module with the current OEM software while on a battery maintainer
  • Load the correct calibration for the vehicle's configuration
  • Repair damaged wiring or connectors
  • Replace or repair the module, then program and match it to the vehicle

Questions and answers

What does P0602 mean?

It means a control module found a programming error: its software or calibration data is corrupt or fails the checksum. It most often shows up after a failed flash or a module replacement.

Can I just clear P0602?

Clearing works only if a one-time power glitch caused it. If the software is corrupt or wrong, the code comes back and the module must be reprogrammed.

Do I need a new ECM for P0602?

Not right away. Check the battery, power and grounds first, then reflash with the correct software. Replacement is needed only if the module's memory has truly failed.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.