OBD Guide
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U1818

Lost Communication With Engine Control Module On Powertrain Expansion Communication Bus

U1818 is an OBD-II diagnostic trouble code meaning: Lost Communication With Engine Control Module On Powertrain Expansion Communication Bus. Common causes: open or short circuit in the can bus, poor contact in ecu connectors. Estimated repair cost: $56–278.

Severity
🔴 High
Can you drive?
Do not drive — repair immediately
Approx. repair cost
$56–278 (est.)

Symptoms

  • Check Engine Light Is On
  • Loss of engine power
  • Unstable engine operation
  • Disabling some vehicle systems
  • Errors in other systems

Causes

  • Open or short circuit in the CAN bus
  • Poor contact in ECU connectors
  • Malfunction of the engine ECU itself
  • Problems with ECU power supply
  • Contact corrosion in wiring harness

How to Fix

  1. Check the integrity of the CAN bus
  2. Inspect the ECU connectors for oxidation
  3. Check the power supply and ground of the ECU
  4. Scan all systems for other errors
  5. If necessary, replace the ECU

Related codes

U0100U0121U0140

FAQ

What does the U1818 code mean?

U1818 is an OBD-II diagnostic trouble code that indicates: Lost Communication With Engine Control Module On Powertrain Expansion Communication Bus

What causes a U1818 error code?

The most common causes of U1818 include: Open or short circuit in the CAN bus; Poor contact in ECU connectors; Malfunction of the engine ECU itself; Problems with ECU power supply.

How do I fix a U1818 diagnostic trouble code?

To fix U1818: Check the integrity of the CAN bus. Inspect the ECU connectors for oxidation. Check the power supply and ground of the ECU. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with U1818?

Do not drive — repair immediately

How much does it cost to fix U1818?

The estimated repair cost for U1818 is $56–278. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat