Replacing Jeep computer

Reply

  #1  
Old 02-12-16, 12:42 PM
Forum Topic Moderator
Thread Starter
Join Date: Mar 2005
Location: USA
Posts: 44,323
Replacing Jeep computer

I replaced the computer this morning on my stepson's jeep. The instructions that came with the computer stated DO NOT disconnect battery before installation! Well that is kind of hard to do since one of the screws holding the computer in place is directly behind the battery. I removed the battery just like I did when I installed the the used computer 2 months ago. I assume it will work just fine.

Any ideas as to why they would have that statement at the top of the installation instructions?
 
Sponsored Links
  #2  
Old 02-12-16, 03:10 PM
Join Date: Jun 2010
Location: Canada (near The Motor City)
Posts: 617
I've read where some vehicles require a 9 volt battery plugged into the cigarette lighter to maintain voltage. What year Jeep is it anyway?

I guess I would find out why they have that statement BEFORE I disconnected the battery ...

Why would you do exactly what they said NOT to do and assume it will work just fine ??

Good luck.
 
  #3  
Old 02-12-16, 03:24 PM
Norm201's Avatar
Member
Join Date: Sep 2013
Location: USA
Posts: 6,196
I have to ask the same question? I understand that you could not place the computer in it's location without removing battery, but did you have to actually make electrical connection with the battery disconnected?
 
  #4  
Old 02-12-16, 03:50 PM
Forum Topic Moderator
Thread Starter
Join Date: Mar 2005
Location: USA
Posts: 44,323
It's 2002 jeep liberty. I replaced the computer [failing coils] 2 months ago with a junkyard computer. It ran great on the that computer but the oil light stayed on constantly [manually checked and found great oil pressure] When his income tax refund came he told me to go ahead and buy a rebuilt one with a warranty. If the old computer isn't returned [received by them] within 14 days of purchase they will charge my CC $100 and void the warranty. This was unknown until the package arrived yesterday.

I was supposed to install it tomorrow but but the highs are expected to be in the teens and I was trying to beat today's snowfall [only half successful] and more snow is expected Sun - Tues Both computers were installed in the exact same manner.
 
  #5  
Old 02-12-16, 04:10 PM
Temporarily Suspended
Join Date: Jul 2008
Location: NY
Posts: 10,986
When the battery is connected, power is always at the alternator & maybe some senors. It could be that when the new computer gets connected, it may have to read some of those sensors & the alternator. You could always reconnect the battery before you connect the computer.
 
  #6  
Old 02-12-16, 04:13 PM
Forum Topic Moderator
Thread Starter
Join Date: Mar 2005
Location: USA
Posts: 44,323
I haven't heard back from him so I assume it's still working fine. At any rate my jeep barely made it up my driveway when I came home - I ain't about to go back out if I don't have to!!
 
  #7  
Old 02-12-16, 04:14 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,637
Forget the battery for now.. Dont you have to progarm that computer? You have to vin check from what I know on the older cars to match the vin #'s to program it with a scan tool...
 
  #8  
Old 02-12-16, 04:18 PM
Forum Topic Moderator
Thread Starter
Join Date: Mar 2005
Location: USA
Posts: 44,323
I had to supply the vin# when I ordered the computer so maybe they did it. With the junkyard computer all I did was hook it up and the jeep ran.
 
  #9  
Old 02-12-16, 04:18 PM
Temporarily Suspended
Join Date: Jul 2008
Location: NY
Posts: 10,986
That's what counts. Stay put if the weather is bad. I'm going to do the same.
 
  #10  
Old 02-12-16, 04:34 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,637
IDK... You went the cheap way out I assume? Just guessing that you said the comp was pre flashed...

Read post here...

I wish I read your other thread regarding this.. I have had experience with this before...

JEEP PCM / ECM...REPLACEMENT LESSON LEARNED - Forums - CNET
 
  #11  
Old 02-12-16, 04:41 PM
Forum Topic Moderator
Thread Starter
Join Date: Mar 2005
Location: USA
Posts: 44,323
We didn't have the time/money to order a new computer back in december and the junkyard computer got him back on the road. The place I ordered the rebuilt computer from did have the lowest price and a lifetime warranty. All the other computers I found only had a 1 yr warranty. Didn't see any new computers for sale - all were rebuilt or used.

This was my first experience working with or replacing a computer.
 
  #12  
Old 02-12-16, 04:49 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,637
he place I ordered the rebuilt computer from did have the lowest price and a lifetime warranty.
Oh ok... Whew......

What do the instructions exactly say???
 
  #13  
Old 02-12-16, 04:53 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,637
Well OBD II says disconnect...


WHEN TO REPLACE YOUR PCM (AND WHEN NOT TO)
 
  #14  
Old 02-12-16, 04:59 PM
Forum Topic Moderator
Thread Starter
Join Date: Mar 2005
Location: USA
Posts: 44,323
Important Installation Information

critical steps
#1 do not disconnect the battery before installation
#2 make sure battery is fully charged and connections are corrosion free, replace battery if 3-4 yrs or older
#3 allow vehicle to run for 15 minutes on first startup

suggested steps
check all grounds and remove any corrosion/oxidation
check for electrical shorts or faulty sensors
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes