OBD Guide

U0640

Lost Communication With EVAP Fuel Vapor Temperature Sensor Circuit

U0640 is an OBD-II diagnostic trouble code meaning: Lost Communication With EVAP Fuel Vapor Temperature Sensor Circuit. Common causes: evap temperature sensor circuit open, short circuit in wiring harness. Estimated repair cost: $17–50.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$17–50 (est.)

Symptoms

  • Check Engine light is on
  • Problems starting the engine
  • Increased fuel consumption
  • Unpleasant smell of gasoline
  • Dips during acceleration

Causes

  • EVAP temperature sensor circuit open
  • Short circuit in wiring harness
  • Fuel vapor temperature sensor malfunction
  • Bad contacts in connectors
  • Problems with the engine control unit

How to Fix

  1. Check the integrity of the wiring harness to the sensor
  2. Inspect and clean the connector contacts
  3. Check the resistance of the temperature sensor
  4. Replace the fuel vapor temperature sensor if necessary
  5. Scan the ECU for additional errors

Related codes

Error U0640 by Vehicle Brand

FAQ

What does the U0640 code mean?

U0640 is an OBD-II diagnostic trouble code that indicates: Lost Communication With EVAP Fuel Vapor Temperature Sensor Circuit

What causes a U0640 error code?

The most common causes of U0640 include: EVAP temperature sensor circuit open; Short circuit in wiring harness; Fuel vapor temperature sensor malfunction; Bad contacts in connectors.

How do I fix a U0640 diagnostic trouble code?

To fix U0640: Check the integrity of the wiring harness to the sensor. Inspect and clean the connector contacts. Check the resistance of the temperature sensor. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with U0640?

Yes, but get it checked soon

How much does it cost to fix U0640?

The estimated repair cost for U0640 is $17–50. Actual cost depends on your vehicle, location, and labor rates.

See also: Russian version · NationStat