Chrysler Repair: P1494 DTC: 99 3.2L

Question
QUESTION: Hi Roland,

Stumbled upon your page while searching online for some tech advice. Read a few of your posts and you really seem to know your stuff!  :-)

I've got a '99 Intrepid ES 3.2L throwing the P1494 "Leak Detection Pump Switch or Mechanical Fault" DTC, but it only does it intermittently from a cold start after the vehicle has not operated for a period of 12 or more hours.

Once the code has been stored, I can clear it & the vehicle will shut-off, start & operate normally around-the-clock without re-triggering the DTC. The code only reappears after the vehicle has not operated for 12 or more hours, but sometimes it doesn't show up at all.

I've inspected the EVAP system for vacuum leaks & electrical issues but can't find anything amiss. Everything functions properly most of the time. Seems like the code should re-trigger consistently & fairly quickly if the pump/vacuum lines/electrical connections were faulty.

Not sure what to try next. Any insights you can offer are much appreciated. Thanks!

Dene

ANSWER: Hi Dene,
The engine controller checks the leak detection pump function only at cold starts which explains the timing of your observation.
The procedure to check out the circuit is:
disconnect the vacuum line at the pump and start the engine and either measure or feel for the presence of a vacuum on the disconnected hose end
then check the leak detection pump switch sense circuit
then check the leak detection pump electrical circuit
then replace the leak detection pump itself.
If still code occurs consider replacing the powertrain control module.
If you don't have the wiring for the system let me know.
Roland

---------- FOLLOW-UP ----------

QUESTION: Wow, you really do know your stuff! Excellent reply & timely, too.

If you can provide the wiring info., that would be great. Thanks!  :-)

Dene

Answer
Hi Dene,
The leak detection pump has a 4-wire plug with three wires.
on pin 2 is a light green/black with 12v via fuse 21 from the ignition switch in the "run" position"
on pin 3 is a white/dark green from pin 77 of the pcm which operates the pump solenoid
on pin 4 is an orange wire from pin 72 of the pcm which is the switch sense circuit.
So check the continuity and also for short circuiting to ground. The wires go through several disconnects so there could be an issue along one of the pathways.
Roland