Computer flash
07-23-2012, 10:37 AM
#1
Member
Thread Starter
Join Date: Mar 2011
Location: Denver, CO
Posts: 190
Likes: 0
Received 0 Likes
on
0 Posts
Year: 2000
Model: Cherokee
Engine: 4.0 Inline 6
Computer flash
I have read the instructions to flash the computer. I installed new injectors and want to flash the computer to adjust for them. However, it says to touch the positive and negative terminals together for 30 seconds. The ground wire for my negative cable is bolted with a rusty bolt that will break if I wrench any further, even with PB blaster, so I cant get it off, which means the cables are too short to get them to touch. If I touch them together with wire or a metal wrench or something, will that have the same effect?
07-23-2012, 10:55 AM
#2
Member
Join Date: May 2012
Location: WoodinVille
Posts: 209
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1994
Model: Cherokee
Engine: 4.0
Simply just un hook your battery, discharge all current that might be in the wires by turning he key. Wait a few min. The hook it all back. Computer reset and you've not fried anything.
07-23-2012, 10:59 AM
#3
CF Veteran
Join Date: Jan 2011
Location: Las Vegas
Posts: 1,894
Likes: 0
Received 4 Likes
on
4 Posts
Year: 1999
Model: Cherokee
Engine: 4.0
21. Disconnect your battery terminals and hold them together for 30 seconds. After those 30 seconds, reattach the terminals to the battery.
22. Turn your ignition to the "ON" position - DO NOT START YOUR JEEP.
23. Turn your headlights on, wait 10 seconds, then turn them off.
24. Turn the ignition to the "OFF" position.
25. Start your Jeep. Your ECU is now reset and will "relearn" the proper fuel trim levels for the new injectors over the next 50 warm up cycles.
22. Turn your ignition to the "ON" position - DO NOT START YOUR JEEP.
23. Turn your headlights on, wait 10 seconds, then turn them off.
24. Turn the ignition to the "OFF" position.
25. Start your Jeep. Your ECU is now reset and will "relearn" the proper fuel trim levels for the new injectors over the next 50 warm up cycles.
07-23-2012, 11:14 AM
#4
Member
Join Date: May 2012
Location: WoodinVille
Posts: 209
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1994
Model: Cherokee
Engine: 4.0
07-23-2012, 11:36 AM
#5
Member
Thread Starter
Join Date: Mar 2011
Location: Denver, CO
Posts: 190
Likes: 0
Received 0 Likes
on
0 Posts
Year: 2000
Model: Cherokee
Engine: 4.0 Inline 6
07-23-2012, 12:04 PM
#6
Member
Join Date: Nov 2010
Location: Salt Lake City, Utah
Posts: 170
Likes: 0
Received 0 Likes
on
0 Posts
Year: 90
Model: Cherokee
Disconnect the cables from the battery. Then discharge the system by turning the ignition to the "On" position and wait for a few minutes. Turn key to the On not the Start position.
Is it the ground pigtail to the body metal that is rusted? If that's the case, then why not go ahead and break it and install another bolt/screw for a known good ground connection to the vehicle. Funky grounds can cause some really irritating issues.
Is it the ground pigtail to the body metal that is rusted? If that's the case, then why not go ahead and break it and install another bolt/screw for a known good ground connection to the vehicle. Funky grounds can cause some really irritating issues.
Last edited by tgordon; 07-23-2012 at 12:07 PM.
Trending Topics
07-23-2012, 01:40 PM
#8
Senior Member
Join Date: Aug 2011
Location: Landers, CA
Posts: 760
Likes: 0
Received 6 Likes
on
5 Posts
Year: Several
Model: Cherokee
Engine: 4.0
None of those will reset the computer on OBDII systems. Internet bull and wishful thinking. Renix there's no long term memory to reset.
Use a scanner capable of getting into the memory - you'll see it does nothing except clear codes temporarily.
You have to disconnect the battery for at least 8 hours to reset the PCM long term memory back to default on OBDII.
You'll have to fix those cables someday - now is a good time.
When you do reset it, it goes back to the original default anyway - not what you want.
Once it runs a few minutes in closed loop, the memory resets itself to the higher flow of the new injectors - it cuts down on open time to achieve Stochiometric.
It will run slightly rich for a short time until it finds the "sweet spot." 5 minutes running it should run fine - it's reset the short term memory.
But the short memory is volatile - turn off the key and it has to start all over.
As you run it, the short term memory slowly trains the long term memory. It may or may not set a code at first - may even set a CEL
As you drive it that info slowly goes into the long term deep memory. Eventually the long term memory becomes totally reset to the new settings. It "learns."
The reason the long term memory does not immediately reset is so you can change batteries and disconnect power to work on it without it totally resetting everything.
The long term remembers things like tire size, TPS voltages, IAT, MAP variatoins, etc.
On some vehicles even "his and hers" AC temps, seat and mirror positions, etc. Fortunately Jeep is not that complicated - yet!
There is lots of wrong internet info - that's why it's good to ask here.
Just drive - it will take care of itself.
Use a scanner capable of getting into the memory - you'll see it does nothing except clear codes temporarily.
You have to disconnect the battery for at least 8 hours to reset the PCM long term memory back to default on OBDII.
You'll have to fix those cables someday - now is a good time.
When you do reset it, it goes back to the original default anyway - not what you want.
Once it runs a few minutes in closed loop, the memory resets itself to the higher flow of the new injectors - it cuts down on open time to achieve Stochiometric.
It will run slightly rich for a short time until it finds the "sweet spot." 5 minutes running it should run fine - it's reset the short term memory.
But the short memory is volatile - turn off the key and it has to start all over.
As you run it, the short term memory slowly trains the long term memory. It may or may not set a code at first - may even set a CEL
As you drive it that info slowly goes into the long term deep memory. Eventually the long term memory becomes totally reset to the new settings. It "learns."
The reason the long term memory does not immediately reset is so you can change batteries and disconnect power to work on it without it totally resetting everything.
The long term remembers things like tire size, TPS voltages, IAT, MAP variatoins, etc.
On some vehicles even "his and hers" AC temps, seat and mirror positions, etc. Fortunately Jeep is not that complicated - yet!
There is lots of wrong internet info - that's why it's good to ask here.
Just drive - it will take care of itself.
07-25-2012, 04:02 PM
#10
Member
Thread Starter
Join Date: Mar 2011
Location: Denver, CO
Posts: 190
Likes: 0
Received 0 Likes
on
0 Posts
Year: 2000
Model: Cherokee
Engine: 4.0 Inline 6
None of those will reset the computer on OBDII systems. Internet bull and wishful thinking. Renix there's no long term memory to reset.
Use a scanner capable of getting into the memory - you'll see it does nothing except clear codes temporarily.
You have to disconnect the battery for at least 8 hours to reset the PCM long term memory back to default on OBDII.
You'll have to fix those cables someday - now is a good time.
When you do reset it, it goes back to the original default anyway - not what you want.
Once it runs a few minutes in closed loop, the memory resets itself to the higher flow of the new injectors - it cuts down on open time to achieve Stochiometric.
It will run slightly rich for a short time until it finds the "sweet spot." 5 minutes running it should run fine - it's reset the short term memory.
But the short memory is volatile - turn off the key and it has to start all over.
As you run it, the short term memory slowly trains the long term memory. It may or may not set a code at first - may even set a CEL
As you drive it that info slowly goes into the long term deep memory. Eventually the long term memory becomes totally reset to the new settings. It "learns."
The reason the long term memory does not immediately reset is so you can change batteries and disconnect power to work on it without it totally resetting everything.
The long term remembers things like tire size, TPS voltages, IAT, MAP variatoins, etc.
On some vehicles even "his and hers" AC temps, seat and mirror positions, etc. Fortunately Jeep is not that complicated - yet!
There is lots of wrong internet info - that's why it's good to ask here.
Just drive - it will take care of itself.
Use a scanner capable of getting into the memory - you'll see it does nothing except clear codes temporarily.
You have to disconnect the battery for at least 8 hours to reset the PCM long term memory back to default on OBDII.
You'll have to fix those cables someday - now is a good time.
When you do reset it, it goes back to the original default anyway - not what you want.
Once it runs a few minutes in closed loop, the memory resets itself to the higher flow of the new injectors - it cuts down on open time to achieve Stochiometric.
It will run slightly rich for a short time until it finds the "sweet spot." 5 minutes running it should run fine - it's reset the short term memory.
But the short memory is volatile - turn off the key and it has to start all over.
As you run it, the short term memory slowly trains the long term memory. It may or may not set a code at first - may even set a CEL
As you drive it that info slowly goes into the long term deep memory. Eventually the long term memory becomes totally reset to the new settings. It "learns."
The reason the long term memory does not immediately reset is so you can change batteries and disconnect power to work on it without it totally resetting everything.
The long term remembers things like tire size, TPS voltages, IAT, MAP variatoins, etc.
On some vehicles even "his and hers" AC temps, seat and mirror positions, etc. Fortunately Jeep is not that complicated - yet!
There is lots of wrong internet info - that's why it's good to ask here.
Just drive - it will take care of itself.
03-15-2019, 03:50 PM
#13
CF Veteran
Why try and reset your ECU anyways? Start it run it and let the fuel trims adjust. It may run rough until the ECU goes into closed loop.
Thread
Thread Starter
Forum
Replies
Last Post
tleed
Stock Grand Cherokee Tech. All ZJ/WJ/WK Non-modified/stock questions go here!
3
10-04-2015 01:20 PM
xjcarolina
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
5
09-29-2015 08:43 PM
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)