96-98 PCM repair procedure W/Pictures - Page 2 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > ZJ Grand Cherokee Forum > 96-98 PCM repair procedure W/Pictures

Rough Country Jeep Suspension Deals at Rockridge 4WD!Engo winches available at www.rockridge4wd.com! Free shippRoad Race Motorsports Stage 2 Power Pack

Reply
Unread 12-19-2011, 11:45 PM   #16
GotMoose
Registered User
1994 ZJ 
 
Join Date: Jul 2009
Location: , California
Posts: 54
Yea, it is likely a custom design for Jeep. Then they are bound by a contract not to tell anyone anything...

GotMoose is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 08:21 AM   #17
ZeeJay1997
Registered User
1997 ZJ 
 
Join Date: Dec 2008
Location: Sweet Home, Alabama
Posts: 6,560
Quote:
Originally Posted by JS97ZJ View Post
ZeeJay, How's your new ride?
My new ride is my old ride... still chugging along without a hitch. Sometime in 1Q12 I will probably swap the ZJ for something more practical and efficient.
ZeeJay1997 is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 10:05 AM   #18
JS97ZJ
Registered User
1997 ZJ 
 
Join Date: Dec 2009
Location: Dingmans Ferry, PA
Posts: 2,035
Quote:
Originally Posted by ZeeJay1997 View Post
My new ride is my old ride... still chugging along without a hitch. Sometime in 1Q12 I will probably swap the ZJ for something more practical and efficient.
I could have used MeanGreen's OBD3 scanner when repairing your unit. It more than likely would have given me more insight as to what was dropping out after 3 days of operating normally.
Being able to re flash it would also taken out the possibility that the programming wasn't the final solution. After re-flowing you unit, it ran like a dream. I guess I'll just have to place yours in the WTF file? (blue screen anomalies)
Is the replacement PCM running without ty's? And one other question. The PCM I worked on...Can you disco the battery to reset it and go for another 3 days before it acts up again?
JS97ZJ is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 12:01 PM   #19
ZeeJay1997
Registered User
1997 ZJ 
 
Join Date: Dec 2008
Location: Sweet Home, Alabama
Posts: 6,560
Quote:
Originally Posted by JS97ZJ View Post
Is the replacement PCM running without ty's? And one other question. The PCM I worked on...Can you disco the battery to reset it and go for another 3 days before it acts up again?
I had to tie one of them because some knucklehead broke the lock tabs off.

In regard to cut offs, it's really wierd. I think it has something to do with the volatile memory because once it starts cutting off (after 3 or so days), although the malfunction resets the monitor circuits to "not ready" (as does disconnecting the battery), the only way to make the malfunction go away, is to disconnect the battery. Go figure...
ZeeJay1997 is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 05:59 PM   #20
coralman
new wrangler prototype
 
coralman's Avatar
1998 ZJ 
 
Join Date: Jul 2010
Location: florida
Posts: 4,522
I've got two from california versions I think. I'm thinkiing about opening one of em. Thr second cardone I have has been doing fine. But you always have that creppy feeling. "Creppy" is my new word,lol, half of creepy and crappy.
coralman is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 09:21 PM   #21
JS97ZJ
Registered User
1997 ZJ 
 
Join Date: Dec 2009
Location: Dingmans Ferry, PA
Posts: 2,035
Quote:
Originally Posted by ZeeJay1997 View Post
I had to tie one of them because some knucklehead broke the lock tabs off.

In regard to cut offs, it's really wierd. I think it has something to do with the volatile memory because once it starts cutting off (after 3 or so days), although the malfunction resets the monitor circuits to "not ready" (as does disconnecting the battery), the only way to make the malfunction go away, is to disconnect the battery. Go figure...
If we knew how long it takes for the PCM to finally settle in after the battery has been disconnected we might have the answer to your PCM's troubles. If it was a component break down I don't think it would take 3 days to show it's face.????
Software glitch?
JS97ZJ is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 09:36 PM   #22
MeanGreenZJ
Web Wheeler
 
Join Date: Apr 2011
Location: Mean Street in a desperate part of town
Posts: 1,710
The PCM settles in after the battery has been disconnected when a drive-cycle has been completed.


Quote:
Originally Posted by JS97ZJ View Post
If we knew how long it takes for the PCM to finally settle in after the battery has been disconnected we might have the answer to your PCM's troubles. If it was a component break down I don't think it would take 3 days to show it's face.????
Software glitch?
MeanGreenZJ is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 09:52 PM   #23
Candymancan
Registered User
1998 ZJ 
 
Join Date: Aug 2010
Location: Virginia
Posts: 3,822
MM i always wondered what they used to keep water out of the PCM, never relised it was encased in 2 inchs of gel on both sides lol
__________________
2013 6.2 V8 Camaro SS 4k miles
1998 5.9 V8 ZJ 160k miles
1998 4.0 I6 Laredo ZJ 210k miles
Candymancan is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 10:03 PM   #24
ZeeJay1997
Registered User
1997 ZJ 
 
Join Date: Dec 2008
Location: Sweet Home, Alabama
Posts: 6,560
This is just a WAG (or something to discuss) based on fighting this thing for 3 years. I think the problem I'm seeing is a malfunction of the circuits or software that does this:

TRIP DEFINITION
The term “Trip” has different meanings depending
on what the circumstances are. If the MIL (Malfunction
Indicator Lamp) is OFF, a Trip is defined as
when the Oxygen Sensor Monitor and the Catalyst
Monitor have been completed in the same drive cycle.
When any Emission DTC is set, the MIL on the
dash is turned ON. When the MIL is ON, it takes 3
good trips to turn the MIL OFF. In this case, it
depends on what type of DTC is set to know what a
“Trip” is.
For the Fuel Monitor or Mis-Fire Monitor (continuous
monitor), the vehicle must be operated in the
“Similar Condition Window” for a specified amount of
time to be considered a Good Trip.
If a Non-Contiuous OBDII Monitor, such as:
Oxygen Sensor
Catalyst Monitor
Purge Flow Monitor
Leak Detection Pump Monitor (if equipped)
EGR Monitor (if equipped)
Oxygen Sensor Heater Monitor
fails twice in a row and turns ON the MIL, re-running
that monitor which previously failed, on the
next start-up and passing the monitor is considered
to be a Good Trip.
If any other Emission DTC is set (not an OBDII
Monitor), a Good Trip is considered to be when the
Oxygen Sensor Monitor and Catalyst Monitor have
been completed; or 2 Minutes of engine run time if
the Oxygen Sensor Monitor or Catalyst Monitor have
been stopped from running.
It can take up to 2 Failures in a row to turn on the
MIL. After the MIL is ON, it takes 3 Good Trips to
turn the MIL OFF. After the MIL is OFF, the PCM
will self-erase the DTC after 40 Warm-up cycles. A
Warm-up cycle is counted when the ECT (Engine
Coolant Temperature Sensor) has crossed 160F and
has risen by at least 40F since the engine has been
started.

This problem never occurs when the Catalyst monitor is not complete. Also it never has pending or active codes prior to or after failure.
ZeeJay1997 is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 10:12 PM   #25
JS97ZJ
Registered User
1997 ZJ 
 
Join Date: Dec 2009
Location: Dingmans Ferry, PA
Posts: 2,035
Quote:
Originally Posted by MeanGreenZJ View Post
The PCM settles in after the battery has been disconnected when a drive-cycle has been completed.
I read an article somewhere that, on GM vehicles, the PCM's need to go through a series of different cycles of idle, acceleration, highway speeds, and slower speeds plus a few on and off cycles before the PCM is considered set to it's optimum proformance levels.
I worked on ZeeJay's unit, and thought that I had it repaired. When I received his, I installed it in my Jeep and it did what I expected it would do, shutting off until the ty-wraps were installed. I ran it for a couple of days and let it kick the hell out of me, then did the repair.
After I re-installed it back in my Jeep, it ran perfectly. If I would have kept it in my Jeep one more day I would have found the symptoms that Zee was getting. Gas gauge was dropping out (at first with no other symptoms) then a stumbling. It wouldn't show up for 3 days. If you reset the system by disconnecting the battery the 3 day cycle would start all over again.
Question here is why 3 days? What is considered a cycle or final cycle that our PCM's need to be finally optimized?
JS97ZJ is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 10:23 PM   #26
JS97ZJ
Registered User
1997 ZJ 
 
Join Date: Dec 2009
Location: Dingmans Ferry, PA
Posts: 2,035
Quote:
Originally Posted by Candymancan View Post
MM i always wondered what they used to keep water out of the PCM, never relised it was encased in 2 inchs of gel on both sides lol
Zee's gel was missing in his PCM. The ASD and 12v regulator chips had been replaced, and as you can see in some of the pictures, the back of his case was cut out and an abortion was performed.
JS97ZJ is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 10:28 PM   #27
ZeeJay1997
Registered User
1997 ZJ 
 
Join Date: Dec 2008
Location: Sweet Home, Alabama
Posts: 6,560
Quote:
Originally Posted by JS97ZJ View Post
Zee's gel was missing in his PCM.
Yeah, i did that...
ZeeJay1997 is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 10:40 PM   #28
MeanGreenZJ
Web Wheeler
 
Join Date: Apr 2011
Location: Mean Street in a desperate part of town
Posts: 1,710
Below is a PDF of the Chrysler drive cycle that lists the conditions that must be met before the PCM is ready with all monitors active after disconnecting the battery.

http://img.neons.org/archives/chrysler_drive_cycle.pdf
MeanGreenZJ is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 10:56 PM   #29
foxman97
Registered User
1997 ZJ 
 
Join Date: Jun 2011
Location: shawnee, oklahoma
Posts: 119
Wow.... Thanks man I really appreciate you going out of your way to do this. Now i only need to find a jy that has and is willing to sell a PCM for my initial screw-up.
__________________
[QUOTE=BlackDaddyZJ;13008903]in all of that i dont hear no, which by my logic and calculations actually means yes:2thumbsup:[/QUOTE]
foxman97 is offline   Reply With Quote Quick reply to this message
Unread 12-20-2011, 11:03 PM   #30
ZeeJay1997
Registered User
1997 ZJ 
 
Join Date: Dec 2008
Location: Sweet Home, Alabama
Posts: 6,560
Quote:
Originally Posted by ZeeJay1997 View Post
This problem never occurs when the Catalyst monitor is not complete. Also it never has pending or active codes prior to or after failure.
Catalyst Monitor Drive Trace
Pre-Conditioning Requirements:
- MIL must be off.
- No DTCs present.
- Fuel level is between 15% and 85% full.
- ECT above 70 F.
- Engine must have run at least 90 seconds
- Engine between 1,350 & 1,900 rpm.

This is interesting because if the fuel is below about 1/4 tank when it fails, the fuel gauge pegs to zero. It also occurs only in the RPM range mentioned above.

So how does a catalyst monitor kill a PCM? (this is a rhetorical question)
ZeeJay1997 is offline   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.