EVAP System - Leak Detection Pump Heater Operation

SOURCE: Kia Technician Times

TITLE: Leak Detection Pump Heater Operation

APPLIES TO: 01 Sephia
01 Spectra

SERVICE TIP:

As reported previously, 2001 model year Sephias and Spectras have a heating element
built into the EVAP system Leak Detection Pump.

The following is to clarify questions we have received regarding the operation logic of the Leak Detection Pump.

Actual operation (energizing) of the heating element for the Leak Detection Pump is tied into the ECM's diagnostic routine for the leak detection; the ECM will only energize the heater (by providing a ground to the circuit) when a leak test can be expected to run afterwards. Since an EVAP leak test is not run after every drive cycle, the heater is not always switched on.

Before the leak detection diagnostic function is "released", certain monitoring conditions have to be met (some twice). Once the initial conditions have been fulfilled, the heater will be switched on shortly after engine start in preparation for the upcoming leak test, and remains on until the ignition key is turned off. Note that additional conditions such as "elapsed time after engine shut off" etc. have to be met as well before the actual EVAP leak test runs. In practice, this means that the heater may be switched on during several consecutive trips (until an EVAP leak test has run) but afterwards it can also mean the heater is not switched on during several trips.

When diagnosing for related DTC's such as P1448 (2001 MY) or P1404 (2002 MY) and when testing the Leak Detection Pump heater function, be aware that the <0.5 Volt reading called for in "idle" mode on the BOB overlay is only obtained during the "heater on" phase. Although not all parameters can be controlled, typically the best time to look for "heater on" status is after refueling; even though the EVAP leak test won't run until the fuel level drops to <85%, the heater will be activated in advance.