Engine

P1602 — Engine Control Module Not Programmed

Severity: medium Drive with care, to a shop

What P1602 means

The engine control module (ECM) found that it has no valid calibration or vehicle data, such as the VIN, in its memory. Normally a new or used module is programmed for the specific vehicle and matched to the immobilizer before use. Without that, the ECM cannot properly control the engine.

Symptoms

  • No-start after ECM replacement
  • Security or immobilizer light on or flashing
  • Check Engine light on
  • Rough or unstable running if the engine does start
  • Other modules cannot communicate with the ECM

Possible causes

  1. New ECM not flashed for this vehicle
  2. Used module from a donor vehicle not adapted
  3. Interrupted programming from a voltage drop or lost connection
  4. Incorrect VIN or calibration data stored in the module
  5. Failed ECM or damaged memory

How to diagnose

  1. Scan all modules and confirm P1602 is current
  2. Find out whether the ECM was replaced or reprogrammed recently
  3. Check battery voltage, terminals and grounds
  4. Compare the VIN and calibration number in the module with the vehicle
  5. Check communication between the ECM, immobilizer and other modules
  6. Inspect ECM power, grounds and connectors for corrosion
  7. Repeat programming using the factory procedure with proper equipment

Common fixes

  • Flash the ECM with the correct calibration for the vehicle
  • Write the VIN and perform immobilizer and key matching
  • Redo an interrupted programming session with stable power
  • Replace a faulty ECM and program the new one
  • Repair power, ground or network wiring problems

P1602 on different brands

Subaru · manuals
Engine control module programming error: the module has not received a valid calibration.
Mazda · manuals
Communication error between the immobilizer module and the engine control module.

Questions and answers

What does P1602 mean?

The engine control module reports that it lacks its calibration or VIN data. It usually appears after the module was replaced or a flash failed.

Can I fix P1602 myself?

Clearing the code will not help, because the module must be programmed for the vehicle. That needs special equipment and software access, so most owners go to a shop.

Why won't my car start with this code?

Without calibration or immobilizer matching, the ECM will not allow the engine to start. This protects against running on invalid data.

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.