gary s

Been working on this for awhile,you think you find something still not it. I thought since the code was basically a pump code I'd just change it to an aftermarket pump bought off ebay. No codes for a couple of weeks but then there it was again. Did a smoke test with a home made smoker built off of youtube and found nothing leaking anywhere on the Jeep,even changed the cap.I found that the wiring plug was loose and the large S shapes hose that connected to the pump seemed cracked,most likely from pulling the old pump off. Replaced the hose and used a cable tie to hold the plug tight, 4 days later the code is back. Does anyone think the new aftermarket pump is bad? Since all signals originate in the pcm could it be bad? Can the plug contacts be bad?,somewhere I saw a replacement plug is available. I guess the next step is to check for continuity and grounds on the wire from the pcm to the pump,I can't see where that could be the problem but I should check.

Ordered it new in March '01

CCKen

Here's some data pertaining to the LDP:

Diagnostics possible causes:

P1494-LEAK DETECTION PUMP SW OR MECHANICAL FAULT

When Monitored: Immediately after a cold start, withbattery/ambient temperature between 40 deg. F and 90 deg. F and coolant temperature within 10 deg. F of battery/ ambient.
Set Condition: The state of the switch does not change when the solenoid is energized.

POSSIBLE CAUSES

WIRING HARNESS INTERMITTENT
LDP SWITCH SENSE CIRCUIT SHORTED TO GROUND
LDP VACUUM SUPPLY
LEAK DETECTION PUMP
LDP SWITCH SENSE CIRCUIT OPEN
POWERTRAIN CONTROL MODULE


Wiring diagram:



.
LDP connector pin out:



.
Note in the wiring diagram that the LDP relay control coil is powered from the generator (I think). You may want to remove the connector and check for voltage at pin cavity 2 in the harness connector with the engine running/alternator on line.

gary s

Thanks,I'm away from it for now but when I get back will check those pins out and see what I'm getting.

gary s

Here is a follow up on my problem. I could not find anything wrong and frankly did not want to throw any more parts at it so I took it in to the dealer. The aftermarket pump was bad so they changed it and that code was now gone. But then p 0456 came back which I have been fighting on and off for a year also. They then smoke checked it changed the gas cap and the solenoid where you connect the smoker to. After a few days light is back on- same code. They said nothing is left in the system except the engine computer. At this point I think I'm good because I took it to a professional,spent over 450 to get it into compliance and no emission parts have been modified or removed so I should be able to get a waiver. Will find out Friday if I qualify

gary s

Decided to take it in for the emissions test,needed to actually fail the test and then show receipts from a qualified mechanic for over $450 to get waiver. Light has gone out again and it passed. If it comes on again I'll guess it's something in the ECM but in the meantime I'm good for 2 more years!

mo8414

Two years to work on moving to another state lol I don't know how you guys can handle having to get checked like that just to drive. I think half the cars in my state would be off the road if that were the case here(michigan) glad you passed for now though

gary s

Yea it is a pain, I do have a winter place in Florida trouble is to license it there I have to drive it there for them to check it out,they won't issue plates with out it being checked. Then with it licensed there I'd have to insure it there too - catch 22. It would not be as bad if they treated you like human being when you go in,you can tell by the pic it's not a beater but they act like your like a criminal. So here is the last follow up- light still comes on and off at time but no codes are present, Si I'm guessing that it must be something in the ECM. If I still have it in 2 years I might just try a reman ECM,I have seen them on ebay for 150

nujeepguy

i looked up the gen, 8w-20-2 in wiring .
i see no reference to evap stuff on this page. no "8w" numbers..

"relay control coil is powered from the generator (I think). Y"
i found nothing about the evep pump like shown here so the wiring is misleading!! wonder where it is connected?
i have a tough time tracing this stuff.jfwiw.

even the ref to s166 takes you back to orig page??