P1494 CHRYSLER, DODGE, JEEP: EVAP LEAK DETECTION PUMP PRESSURE SWITCH CONDITION
POST UPDATED IN May, 2023
P1494 CHRYSLER, DODGE, JEEP: EVAP LEAK DETECTION PUMP PRESSURE SWITCH CONDITION
The EVAP (evaporative emission control system) system captures and keeps fuel vapors in a sealed tank. In this way, they cannot escape into the environment. Although these systems generally use a vacuum to check the system for proper operation, many manufacturers use an air pump. This air pump is known as a leak detection pump. To determine if fuel vapors are leaking, the air pump pressurizes the system to around 0.25 PSI during the self-tests
A diaphragm operates the leak detection pump. It consists of a sealed vessel divided into two halves by the diaphragm, which has a constant pressure by a spring. The lower half is connected to the EVAP. One side of the diaphragm has an opening to allow atmospheric air to enter. On the other hand, the upper half is connected to the engine vacuum, and one side to the atmospheric opening.
The pump diaphragm is connected to a metal shaft. It activates an on/off switch as the diaphragm moves up and down during the pumping process. The PCM uses this switch for diagnostic purposes but also to know the position of the diaphragm regarding the PCM. This position is the basis for a pump solenoid activation mechanism during a normal operating condition.
If the PCM has detected that the reed switch or leak detection pump control switch has not changed once the self-test process has begun because of a failure of the solenoid, the control circuit, or the diaphragm itself, the fault code P1494 OBDII will be set.
Reasons to set the P1494 OBD2 DTC P1494 OBD2 code :
Steps to troubleshoot the P1494 OBDII diagnostic code: