Electrical and sensors

P0605 — Control Module Read Only Memory (ROM) Error

Severity: medium Drive with care, to a shop

What P0605 means

During self-tests, the engine or powertrain control module verifies that the program and calibration data stored in its read-only memory (ROM) are intact. P0605 is set when that check fails because the data is corrupted or unreadable. The module may then control fuel, ignition, transmission or other functions incorrectly.

Symptoms

  • Check Engine light on
  • No-start or intermittent starting
  • Hesitation, power loss or limp mode
  • Unstable idle
  • Wrong shifting if the transmission module is affected
  • Sometimes no noticeable symptoms, depending on the affected function

Possible causes

  1. Internal failure of the control module
  2. Failed or interrupted software flash
  3. Low or unstable supply voltage during operation or programming
  4. Poor power or ground connections to the module
  5. Outdated or faulty software
  6. Water intrusion or corrosion inside the module

How to diagnose

  1. Scan all modules, save freeze frame data and note related power or communication codes
  2. Test battery condition and charging system voltage
  3. Check fuses, power feeds and grounds to the module, and inspect connectors for corrosion or moisture
  4. Inspect the module housing and connector for water, heat damage or signs of prior repair
  5. Check the software version and look for manufacturer service bulletins
  6. Clear the code and see whether it returns under the same conditions
  7. If it is persistent, have the module assessed by a shop with programming tools

Common fixes

  • Repair power supply and ground problems
  • Replace or charge the battery and fix any charging system fault
  • Reflash the module with current software at a dealer or properly equipped shop
  • Repair or replace the module, then program it to the vehicle

Questions and answers

What does P0605 mean?

The control module found an error in its read-only memory, where its program and calibrations are stored. It points to an internal fault or a failed software update.

Do I need to replace the module for P0605?

Not always. Check power, grounds, the battery and software updates first. If the code returns after clearing and reflashing, the module is usually repaired or replaced and programmed.

Can I drive with P0605?

Only carefully and to a shop. The car may go into limp mode or refuse to start, so do not put off diagnosis.

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.