My vehicle is a 1999 dodge 2500 club cab with the v-10 engine. I plugged my $100 dollor scanner in and retrieved the p1494 code. My tool descibed this as, leak detection pump switch or mechanical fault. Furture search revieled, manufacturers controlled auxilliary emission controls. Can anyone help me with an avenue to repair. Thanks

It's pretty difficult to figure that one out unless you have an enhanced scan tool that can enable the LDP test while you watch the switch state of the reed switch to see if it changes states.

Basically the LDP (Leak detection pump) is used to check for leaks in the EVAP system. The pump uses engine vacuum and a solenoid to control a diaphram pump. The pump shaft itself is attached to a reed switch that opens and closes as the diaphram moves. The pump actually pressurizes the EVAP system to check for leaks by monitoring the time the switch opens and closes. When the switch fails the engine computer can't run the test because it doesn't know what position the pump is in or if it is even working. The reed switch is inside the LDP.

I am not going to say the LDP is the problem, but most of the time it is. About all you can do is check the vacuum hose to be sure there is vacuum at the pump and inspect the electrical connector on the solenoid unless you can get hold of a scan tool and wiring schematic for the EVAP system.













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(This post was edited by Discretesignals on Jan 27, 2012, 6:59 PM)

   Once again you've been able to lead me to my problem. I inspected the vacuum system and found the vac. hose on the bottom of the throttle body had dropped off. great job.