OBD Guide
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P1681

Control Module Not Programmed

P1681 is an OBD-II diagnostic trouble code meaning: Control Module Not Programmed. Common causes: replaced ecu without programming, ecu software failure. Estimated repair cost: ~$556.

Severity
🔴 High
Can you drive?
Do not drive — repair immediately
Approx. repair cost
~$556 (est.)

Symptoms

  • Engine won't start
  • Check Engine Light Is On
  • Loss of engine power
  • Incorrect transmission operation
  • Malfunctions of the car's electronic systems

Causes

  • Replaced ECU without programming
  • ECU software failure
  • Problems with ECU power supply
  • Unsuccessful attempt at flashing
  • ECU memory damage

How to Fix

  1. Check battery voltage and ECU power supply circuit
  2. Read all error codes using a diagnostic scanner
  3. Check the repair history to see if the ECU needs to be replaced
  4. Reprogram the ECU at an authorized dealer
  5. If necessary, replace the ECU

Related codes

P1682P1683P1684

Error P1681 by Vehicle Brand

AcuraBuickCadillacChevroletChryslerDodgeGMGMCHondaInfinitiJeepOldsmobilePlymouthPontiacSaturnVolkswagen

FAQ

What does the P1681 code mean?

P1681 is an OBD-II diagnostic trouble code that indicates: Control Module Not Programmed

What causes a P1681 error code?

The most common causes of P1681 include: Replaced ECU without programming; ECU software failure; Problems with ECU power supply; Unsuccessful attempt at flashing.

How do I fix a P1681 diagnostic trouble code?

To fix P1681: Check battery voltage and ECU power supply circuit. Read all error codes using a diagnostic scanner. Check the repair history to see if the ECU needs to be replaced. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P1681?

Do not drive — repair immediately

How much does it cost to fix P1681?

The estimated repair cost for P1681 is ~$556. Actual cost depends on your vehicle, location, and labor rates.

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