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Discussion Starter · #1 ·
A couple years ago my Jeep Liberty blew a head gasket, so I did the head gasket job and all went well. It ran perfectly for a few months then one day I started it up to move it for snow removal and it stalled, hasn't started since. I ran the codes, replaced nearly all the sensors but still nothing. Ran the codes again, there aren't any so a friend suggested it could be the ECM so I bought a rebuilt one with identical numbers to save a few hundred $. Installed it and still nothing. Talked to a local mechanic who suggested the ECM needs to be taken to a certified MOPAR dealer to have it flashed. Has anyone ever encountered this, know anything about it? Does this sound like it might be worth a try? Lost here but don't want to give up on it as it's a great little Jeep.
 

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Knowing some details would help us help you.
Jeep cranks over but will not start at all ?

what model year (MY) and which eng trans?

You claim you changed sensors WHY?

Do you have a scanner or code reader or ?


KEEP YOUR ORIGIONAL MODULE....
 

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some info I see now ..... this is a

2002 liberty could this be a diesel engine ? :dunno:
 

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Discussion Starter · #4 ·
I have a code reader, wish I had a scanner, and the codes thrown at first suggested either one of the in or out engine speed sensors, since they are relatively inexpensive I replaced both. Engine cranks but won't start or fire at all, fuel rail has plenty of pressure. So then I replaced the cam position sensor, still nothing. The last time I hooked up my code reader I got nothing so I discussed this with a few friends of mine who are quite mechanically inclined and 2 of the 3 said they think it is probably the ECM, one of them said it might even be the smart key but i have 2 smart keys and it won't start with either.

This is a 2002 Jeep Liberty Sport with the 3.7L engine, gas fired, auto transmission.

I would greatly appreciate any help/tips.
 

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If you can post fuel PSI -
spec is (49.2 psi +/–5 psi) And cold weather is demanding.
IIRC there is a schraider valve on fuel rail fuel pressure gauges are available as a loaner or rental.

- There is a quick test we use - as someone tries to start jeep spray carb clean, starting fluid into TB, did the engine fire and try to start?
- OR with a good scanner look at fuel trims a large correction + would make pump suspect.

When you are crankiing engine are the injectors pulsing - use a noid light OR remove inj connector and jump the 2 wires with a test light - flashing as someone cranks eng? this will tell us if PCM is controlling system.


TMI:
FYI you don't have an ECM you have a PCM - acronym overload.
ECM is a term related to diesels. Why make things simple IDK.

You say smart key, the system is 'SKIS' - there is a key shaped symbol in gauge cluster. The Skis will not prevent starting how it operates is the engine would start for @3 seconds then shut down as the system disables injectors. Ther would be illuminated or flashing key symbol.

Where did you get a PCM? I think only a junk yard would sell an unflashed unit

KEEP THE ORIGINAL PCM! let me know if you have it.
 

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Discussion Starter · #6 ·
I bought the PCM from www.moduleexperts.com and I do still have the original one. I just visited their website again and found a page that suggests the PCM I got from them will need to be programmed/flashed, apparently everything newer than 1996 isn't a plug n play thus will need to be programmed/flashed. I submitted a question to their "Contact" page asking if I need to get it programmed/flashed from a certified Jeep Dealer Service Center. Hopefully I will hear back from them soon. I should have contacted them a couple years ago when I first installed the unit I bought from them but it wasn't until recently when I learned of the possible need for programming or flashing. It seems I recall the salesman telling me as long as the numbers are identical it should work. ?? I am far from an electronics whiz. Sometimes I wish I could just find a 1970's model Jeep in great shape and sell all my newer electronic controlled vehicles, it was so much easier to diagnose and repair them.

I will have to see if some of the parts stores around the area will loan me a fuel pressure guage. "starting fluid into TB", I don't know what the TB is, at least I don't think I know or just don't recognize the acronym.

OK, so it sounds like the "smart key" is not a possibility.
 
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