OBD Guide
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P1803

Immobilizer ECU Signal Error

P1803 is an OBD-II diagnostic trouble code meaning: Immobilizer ECU Signal Error. Common causes: malfunction of the immobilizer control unit, damage to the key reader antenna. Estimated repair cost: $33–167.

Severity
🔴 High
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$33–167 (est.)

Symptoms

  • Engine won't start
  • The engine stalls immediately after starting
  • The immobilizer indicator is flashing
  • No response when turning the key
  • Immobilizer error message on dashboard

Causes

  • Malfunction of the immobilizer control unit
  • Damage to the key reader antenna
  • Dead battery in the ignition key
  • Damage to the transponder chip in the key
  • Problems with system wiring or connectors

How to Fix

  1. Check the battery in the ignition key
  2. Diagnose the immobilizer control unit
  3. Check the integrity of the reader antenna
  4. Check the condition of the wiring and connectors
  5. Reprogram keys or control unit
  6. Repair only from an authorized dealer

Related codes

P0513P0633P1610

FAQ

What does the P1803 code mean?

P1803 is an OBD-II diagnostic trouble code that indicates: Immobilizer ECU Signal Error

What causes a P1803 error code?

The most common causes of P1803 include: Malfunction of the immobilizer control unit; Damage to the key reader antenna; Dead battery in the ignition key; Damage to the transponder chip in the key.

How do I fix a P1803 diagnostic trouble code?

To fix P1803: Check the battery in the ignition key. Diagnose the immobilizer control unit. Check the integrity of the reader antenna. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P1803?

Yes, but get it checked soon

How much does it cost to fix P1803?

The estimated repair cost for P1803 is $33–167. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat