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Hey guys, I've got a 00 Dakota sport quadcab 4x4 with a 4.7. I've got a p1494 code that I can't figure out. I've tested the leak detection pump by putting a balloon on the canister side of the pump and then applying 12 v power to the proper pin and grounding the correct pin while having the vacuum line connected to the intake. This allows the balloon to inflate and hold the pressure when I remove the ground. I believe this means the LDP is good as far as functioning goes. I then tested power to the connector with the truck running. I have 12+ volts on the correct pin but I never seem to get the ECU to ground the ground pin. After a few minutes I get the p1494 code before the pump ever even functions. I have pulled the connector at the ecu and checked continuity between the LDP connector and ecu with no breaks between the corresponding wires. This leaves me to believe the ECU has an internal problem. Can anyone help confirm that has a better understanding of how the ECU sends ground? I don't want to buy a new ECU until I'm more confident I'm not missing something. Thanks guys.
You've probably seen this site in your searches, but it says the PCM is your least likely failure point. Not sure how accurate your balloon test will be. Maybe it will pump up the balloon, but not function enough to satisfy system requirements. First thing I'd do is check all the emission hoses, then head to a junkyard to snag a LDP. It is a very widely used part across many vehicle, so chances are you won't have a problem finding it and for cheap.
"Typical causes of P1494 could include the following-
Defective Leak Detection Pump
Damaged, burnt, shorted, disconnected, or corroded wiring in the LDP Switch Control Circuit, or in one or more control circuits of sensors that supply input information to the LDP/PCM. Refer to the manual for detailed information on which sensors could be implicated in setting P1494 on the application being worked on.
Damaged, restricted, dislodged, or leaking vacuum lines
Failed, or failing PCM. Note that this is a rare event, and the fault must be sought elsewhere before any controller is replaced."
Copied from an old post of mine....
Originally Posted by Dodgevity
Concentrate on these two things.... emission hoses and leak detection pump.
I had that code intermittently for years. It would come and go, but I was always able to find a window in which to get the emissions done.
I got tired of the light every few months though, so I started looking at all the hoses running from under the battery tray and found a cracked hose there and on a hose that ran to the PCV valve (if I recall correctly). I never would have known the hose was split if I didn't squeeze it, so squeeze and observe as you go along. It's usually the ends that crack. I cut the split ends off with a knife and reattached with zip ties. Also looked under the truck at the hoses running to charcoal canister and those seemed okay. Well the problem lessened in frequency, but didn't entirely go away. The final fix was to replace the NVLD pump (leak detection pump), which is located underneath the truck, roughly below the drivers seat in my quad cab.
The pump was one I got from a wrecked 2009 Chrysler PT cruiser. The pump is WIDELY used across many models and years of Chrysler vehicles, so I found the latest model vehicle that had one in the junkyard and it worked. Cost me only a few bucks and not a peep out if it since. If you search on the pump in ebay, it will show you the models that it fits. There are many aftermarkets (cheap too) but I stick to OEM with these things.
Last edited by Dodgevity; Jun 17, 2020 at 09:40 AM.
Dodgevity, thanks for the reply. I ended up picking up a used ldp from the junkyard and ran in to the same problem. both coils on the solenoid showed the same resistance and both seemed to function properly. I was about to throw in the towel and take the truck in but decided to do some more research. I found that the reed valve has a sensor on it that sends a signal to the computer telling it which state open or closed it is in. I bit the bullet and bought a new pump for $300 and it did the trick. I guess even though both LDP's functioned fine the switch in the reed on both were faulty and the computer did not like that. thanks again for the reply!
Pesky P1494
