Initial Inspection and Diagnostic Overview: Overview

Evaporative Emissions

Overview

There are changes to the Federal evaporative emission system for 2006 in both hardware and software, although Europe remains unchanged.

The hardware changes to the Federal evaporative emissions system (EVAP) are the deletion of the canister close valve and the fuel tank pressure sensor, which have been replaced with a combined unit incorporating a DMTL (diagnostic monitoring of tank leakage) pump and a COV (change-over valve) into one module.

The software changes will have more effect on the technician, as there is no longer the need to carry out extensive drive cycles to confirm the success of a repair.

DMTL conditions

The DMTL test is performed after the engine has stopped following a 10 minutes run, providing that the vehicle fuel tank is between 15 and 85 percent full and that the ambient temperature is above 0 degree C (32 degrees F) and less than 40 degrees C (104 degrees F).

The DMTL pump is driven to pressurize the fuel tank and the current is measured with the change-over valve in different states.

A comparison of the current draw in each state indicates the degree of any leak, and the ECM then sets the appropriate DTC.