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Unread 08-09-2008, 12:48 PM   #1
eparke
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Does PCM Need to be Programmed?

I did not get any replies on my last post - perhaps it was kind of vague or redundant to other posts?
Anyway, I am wits end with this jeep - 1997 Grand Cherokee with a 5.2 liter motor.
I took it to the dealer and the invoice reads: "No response from PCM, Test powers and grounds, all good. Check Communication with cluster and VTSS=OK Suspect Bad PCM".
They want to replace the PCM at $685.00 but I am hesitant, and this is why: I walked back into the shop area - you know, where customers are not supposed to go. I see this sign that says, "UPSELL". I am not kidding. I asked the service guy about it and he just laughed it off.
So now I am not sure if they are really telling me the truth, or just trying to "UPSELL" me. I told him I could get a PCM from Napa for just over $200 and he said that I would still need to bring the jeep to the dealer to have it programmed. Does anyone know of any truth to this?

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Unread 08-09-2008, 01:09 PM   #2
tiggamonsta
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Not sure if this helps, but this is from Autozone's website.

...The PCM is a pre-programmed, dual microprocessor digital computer...


Leads me to think you do not need to program it.
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Unread 08-09-2008, 01:18 PM   #3
nashmd454
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the best thing you can do is look at the pcm you have and get the #'s off of it...then go on ebay and find one that is similar (identical) and get it for about $150...way less than the stealership...and it is so easy to install. There you go.
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Unread 08-09-2008, 01:32 PM   #4
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The one I got from the stealership was like half that, brand new, and programmed. Not sure what UPSELL is, but seems like they're trying to rape you for cash
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Unread 08-09-2008, 02:07 PM   #5
95ZJL
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absolutely not there is no need to reset or reprogram that ecu if you disconnect it from the main harness it automatically resets itself. Once it is reconnected your air/fuel will be off whack until it adjusts
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Unread 08-09-2008, 03:02 PM   #6
EagleStorm
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you will need to program in the VIN but a 97 jtech pcm comes programed
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Unread 08-09-2008, 06:23 PM   #7
ratmonkey
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98+ you need to program the vin into it.
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Unread 08-09-2008, 07:01 PM   #8
eparke
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Maybe PCM is not bad?

Okay, I located a used PCM to troubleshoot my problem here and there is no change in behavior from this jeep with the "New" PCM.
My neighbor keeps telling me to change the cps even though when I checked it out with the meter according to the Chilton manual, it seemed to be fine.
I do remember working with the stator on my ATV and I seemed to be happy with what the volt meter was telling me, but I changed out a coil in the stator and it fixed the problem. Has anybody tried checking the cps with a meter and it looked good but still turned out to be bad?
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Unread 08-09-2008, 09:28 PM   #9
VulcanJeep
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The only 100% real way to check the CPS is to stick a new one in. You might want to carry a spare anyhow...
UPSELL?? I wouldn't be giving that dealer any of my business! Take a photo of that sign, and see if the media wants it.
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Unread 08-10-2008, 06:40 AM   #10
Kolak
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Any replacement PCM should be reprogrammed with the correct VIN and mileage. On occasion, VIN mismatches will cause odd behavior.

That said, what are your symptoms? What code(s) are stored?

"Upsell" doesn't necessarily mean they're trying to sell you something they don't think you need, but rather means they are to suggest other maintenance procedures that might need attention at a specific mileage level. That's just sales talk - at restaurants for example, when you order an entree they tell the staff to suggest a glass or bottle of wine -that's a form of upselling.
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Unread 08-10-2008, 09:17 AM   #11
eparke
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The symptoms are:

1. I cannot get any codes. The battery is good, the connections are good. The starter turns the engine over fine, but it will not fire. I don't get a "Check Engine" light, but do get a "Check Gauges" light.

2. I know there is gas in the tank, but the gauge shows none. I turn the key on and the gas light goes out but comes back on in about 3-5 seconds. Before I took it to the dealer, I would get the fuel pump to come on sporadically. Now it comes on every time I turn the key to the run position.

3. The red alarm L.E.D. on top of the dash does not flash when the alarm is set with the door or the remote like it used to. Also, when the key is turned to the run position, the red L.E.D. will come on solid red after about 30 seconds.

4. The dealer checked all grounds and power and all seemed to be good. The invoice reads, "No response from PCM, test powers and grounds, all good. Check communication with cluster and VTSS=OK suspect bad PCM".

5. I tried a different PCM (used) but I get the exact same symptoms with both PCM's. If I am frying the PCM, I don't want to buy a new one just to ruin it also.

At this point, I am thinking to change out the CPS just to eliminate that as a possibility - even though it checks out to be okay using the ohm and volt meters.
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Unread 08-10-2008, 09:21 AM   #12
eparke
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Another thing I see as a potential problem

Another thing is that it loads up on gasoline. If I leave the key switch on, the fuel pump does not turn off after the few seconds (I believe it is supposed to?). And the cylinders seem to load up on fuel, eventually making it impossible to turn over the engine due to too much fuel in the combustion chamber. I have to remove the spark plugs and turn the engine over to pump out all of the gasoline.
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Unread 08-10-2008, 09:46 AM   #13
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Quote:
Originally Posted by eparke View Post
Another thing is that it loads up on gasoline. If I leave the key switch on, the fuel pump does not turn off after the few seconds (I believe it is supposed to?). And the cylinders seem to load up on fuel, eventually making it impossible to turn over the engine due to too much fuel in the combustion chamber. I have to remove the spark plugs and turn the engine over to pump out all of the gasoline.
I believe that is virtually impossible with fuel injection. The injectors would have to be stuck open for any fuel to get in the cylinders. The injectors are closed until you start cranking the engine. The pump is running for a few seconds to build the fuel pressure in the fuel rail. Then it shuts off until you start the engine.
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Unread 08-10-2008, 11:35 AM   #14
jeepinjoe123
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sounds like cps to me look up no-bus happens alot in the cherokees fixed a friends jeep that was doin the same stuff gas gauge and stuff wouldnt work on that either
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Unread 08-10-2008, 01:08 PM   #15
EagleStorm
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Take it to the dealer let them replace the pcm but when they write up the repair order bring up the point that if it dont fix it you dont pay It's there diag your going on if they are wrong you have all ready paid for the diag If the part they replace dont fix it they can remove it be nice not pissy do the asking before you put you name on the RO if they dont agree then they are not sure of there diag
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