Help abs lock and wont turn off, cherokee wont even roll
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Newbie
Joined: Jan 2020
Posts: 11
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From: Michigan
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0
I read something about it last night before I posted my last message. I know a little about all of the different computers (ECUs) on these Jeeps, and for vehicles in general. What I read makes sense to me with what I know.
It was saying there is a dedicated primary ECU (a non-PCM ECU) to also throw a code for in these situations. There is also a backup ECU to throw a code for the first primary non-PCM ECU.. to throw a code in this situation should the first ECU have been taken out by a high surge of electricity somehow in some way... There is a chain reaction of events.
The different sources all mentioned the ABS Module (this module is just one of many Primary ECUs.. second in command behind the PCM of course). They say in general the ABS Module is ussually on the top of the list as a module to be reporting a problem by throwing a code when there is an issue with alternator fielding and the pulse width modulation communication to the PCM. So, it makes sense why your Jeep had its ABS Module freakout during the episode, and for why it has a code remaining afterwords.
In semi-modern vehicles, the first suspect is always the PCM. This is because the alternator fielding is regulated internally by the PCM. I believe there are ways to test your PCM to see exactly what is happening inside of it right now. I still would not want to mess around and would not recommend attempting any diagnosis or any fix to this other than maybe trying to replace the PCM and see if it goes away. It is not that the regulator pulse width modulation function has failed.. It is a loss of communication on the pathway between the alternator and regulator function of the PCM and the whole PCM interface to it.
I do not understand it all? I have not really looked into trying and understanding it in all honesty. I am not sure what type of back-up plan is in place for in this situation. Maybe there is a set charge rate in play now? The alternators charge rate effects the vehicles fueling, timing, spark, air-intake, and overall engine functions... If certain accessories are on that require more electrical energy such as air conditioners, high beams, the heater, radio amps, a winch, a snow plow, old-school police lights & sirens, etc... The alternator needs to work harder and the different engine functions all need to pick-up to compensate for this.
It is a bit involved all of the circuitry involved on this particular malfunction.
I do not think it matters what type of battery you have when it comes to super-heating the internals. The amplitude of this type of electricity is able to cause major destruction to occur. The by-products are highly explosive. Although, I am not sure what type of worst-case explosion could result? I would not want to find out personally first-hand. If it were to happen while driving... It would not take much to have a fateful outcome. The implications are disastrous.
It was saying there is a dedicated primary ECU (a non-PCM ECU) to also throw a code for in these situations. There is also a backup ECU to throw a code for the first primary non-PCM ECU.. to throw a code in this situation should the first ECU have been taken out by a high surge of electricity somehow in some way... There is a chain reaction of events.
The different sources all mentioned the ABS Module (this module is just one of many Primary ECUs.. second in command behind the PCM of course). They say in general the ABS Module is ussually on the top of the list as a module to be reporting a problem by throwing a code when there is an issue with alternator fielding and the pulse width modulation communication to the PCM. So, it makes sense why your Jeep had its ABS Module freakout during the episode, and for why it has a code remaining afterwords.
In semi-modern vehicles, the first suspect is always the PCM. This is because the alternator fielding is regulated internally by the PCM. I believe there are ways to test your PCM to see exactly what is happening inside of it right now. I still would not want to mess around and would not recommend attempting any diagnosis or any fix to this other than maybe trying to replace the PCM and see if it goes away. It is not that the regulator pulse width modulation function has failed.. It is a loss of communication on the pathway between the alternator and regulator function of the PCM and the whole PCM interface to it.
I do not understand it all? I have not really looked into trying and understanding it in all honesty. I am not sure what type of back-up plan is in place for in this situation. Maybe there is a set charge rate in play now? The alternators charge rate effects the vehicles fueling, timing, spark, air-intake, and overall engine functions... If certain accessories are on that require more electrical energy such as air conditioners, high beams, the heater, radio amps, a winch, a snow plow, old-school police lights & sirens, etc... The alternator needs to work harder and the different engine functions all need to pick-up to compensate for this.
It is a bit involved all of the circuitry involved on this particular malfunction.
I do not think it matters what type of battery you have when it comes to super-heating the internals. The amplitude of this type of electricity is able to cause major destruction to occur. The by-products are highly explosive. Although, I am not sure what type of worst-case explosion could result? I would not want to find out personally first-hand. If it were to happen while driving... It would not take much to have a fateful outcome. The implications are disastrous.
I just ordered a plug and play ECM (I hope that’s right because I can only find results for TCMs and ECMs) if that’s wrong stop me soon so I don’t end up with the wrong part coming in. Will keep you updated on the results of that
Banned
Joined: Feb 2019
Posts: 1,359
Likes: 169
From: NC
Year: 2004
Model: Grand Cherokee (WJ)
Engine: 4.0
It sounds right. They come as plug & play. ECM Electronic Control Module and ECU Electronic Control Unit and PCM Powertrain Control Module are all synonymous to mean the main engine computer. I wish they would always say PCM because that is the actual correct terminology for the part. But, it is usually ECM or ECU. Any part on your Jeep that ends with 'Module' is also an ECU or ECM. Only the PCM is the dedicated term used for being the main engine computer.
As an aside.. In medicine there are terms used to describe an abnormal heart rhythm. Many many practitioners use the term 'arrhythmia' to describe this.. It is wrong though. 'A-' means 'abscense of' when it is attached to the front of a word like that. If someone has an abscense of a heart rhythm, they not only have an abnormal heart rhythm.. in fact, what they have is a heart that is no longer beating is what they got. The correct terminology is dysrhythmia. A little nitpicky and all since everyone uses the two terms interchangeably. That, and a true cardiac flatline is namely called asystole instead of an arrhythmia. It is just one thing a professor of mine made a point on when we were learning about the heart. A little off-track there but, same similar thing...
Back to your ECM.. After the purchase, have you been asked for the VIN and mileage of your Jeep?
As an aside.. In medicine there are terms used to describe an abnormal heart rhythm. Many many practitioners use the term 'arrhythmia' to describe this.. It is wrong though. 'A-' means 'abscense of' when it is attached to the front of a word like that. If someone has an abscense of a heart rhythm, they not only have an abnormal heart rhythm.. in fact, what they have is a heart that is no longer beating is what they got. The correct terminology is dysrhythmia. A little nitpicky and all since everyone uses the two terms interchangeably. That, and a true cardiac flatline is namely called asystole instead of an arrhythmia. It is just one thing a professor of mine made a point on when we were learning about the heart. A little off-track there but, same similar thing...
Back to your ECM.. After the purchase, have you been asked for the VIN and mileage of your Jeep?
Thread Starter
Newbie
Joined: Jan 2020
Posts: 11
Likes: 0
From: Michigan
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0
It sounds right. They come as plug & play. ECM Electronic Control Module and ECU Electronic Control Unit and PCM Powertrain Control Module are all synonymous to mean the main engine computer. I wish they would always say PCM because that is the actual correct terminology for the part. But, it is usually ECM or ECU. Any part on your Jeep that ends with 'Module' is also an ECU or ECM. Only the PCM is the dedicated term used for being the main engine computer.
As an aside.. In medicine there are terms used to describe an abnormal heart rhythm. Many many practitioners use the term 'arrhythmia' to describe this.. It is wrong though. 'A-' means 'abscense of' when it is attached to the front of a word like that. If someone has an abscense of a heart rhythm, they not only have an abnormal heart rhythm.. in fact, what they have is a heart that is no longer beating is what they got. The correct terminology is dysrhythmia. A little nitpicky and all since everyone uses the two terms interchangeably. That, and a true cardiac flatline is namely called asystole instead of an arrhythmia. It is just one thing a professor of mine made a point on when we were learning about the heart. A little off-track there but, same similar thing...
Back to your ECM.. After the purchase, have you been asked for the VIN and mileage of your Jeep?
As an aside.. In medicine there are terms used to describe an abnormal heart rhythm. Many many practitioners use the term 'arrhythmia' to describe this.. It is wrong though. 'A-' means 'abscense of' when it is attached to the front of a word like that. If someone has an abscense of a heart rhythm, they not only have an abnormal heart rhythm.. in fact, what they have is a heart that is no longer beating is what they got. The correct terminology is dysrhythmia. A little nitpicky and all since everyone uses the two terms interchangeably. That, and a true cardiac flatline is namely called asystole instead of an arrhythmia. It is just one thing a professor of mine made a point on when we were learning about the heart. A little off-track there but, same similar thing...
Back to your ECM.. After the purchase, have you been asked for the VIN and mileage of your Jeep?
Banned
Joined: Feb 2019
Posts: 1,359
Likes: 169
From: NC
Year: 2004
Model: Grand Cherokee (WJ)
Engine: 4.0
It sounds like you definitely have the correct part coming to you if they asked all of those things.
I have good belief replacing the PCM will resolve the whole issue for you too. Seeing as how nearly 100% of all modern vehicles today presenting with this code it is a PCM issue. The odds alone are very much in your favor for it to be the reason. The serpentine belt problem happening like it did is the only reason why I have a shadow of doubt. A lot of different things could have taken place over time because of this. It may have been better for you if the serpentine belt would have just thrown itself off instead. Who knows how long it was actually happening prior to the major symptoms experienced? It could have been occuring for some time, and it may have been demanding unreasonable expectations out of the charging system if it was an ongoing issue that was happening.
I have good belief replacing the PCM will resolve the whole issue for you too. Seeing as how nearly 100% of all modern vehicles today presenting with this code it is a PCM issue. The odds alone are very much in your favor for it to be the reason. The serpentine belt problem happening like it did is the only reason why I have a shadow of doubt. A lot of different things could have taken place over time because of this. It may have been better for you if the serpentine belt would have just thrown itself off instead. Who knows how long it was actually happening prior to the major symptoms experienced? It could have been occuring for some time, and it may have been demanding unreasonable expectations out of the charging system if it was an ongoing issue that was happening.
Last edited by Noah911; Jan 5, 2020 at 12:11 PM.
Thread Starter
Newbie
Joined: Jan 2020
Posts: 11
Likes: 0
From: Michigan
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0
It sounds like you definitely have the correct part coming to you if they asked all of those things.
I have good belief replacing the PCM will resolve the whole issue for you too. Seeing as how nearly 100% of all modern vehicles today presenting with this code it is a PCM issue. The odds alone are very much in your favor for it to be the reason. The serpentine belt problem happening like it did is the only reason why I have a shadow of doubt. A lot of different things could have taken place over time because of this. It may have been better for you if the serpentine belt would have just thrown itself off instead. Who knows how long it was actually happening prior to the major symptoms experienced? It could have been occuring for some time, and it may have been demanding unreasonable expectations out of the charging system if it was an ongoing issue that was happening.
I have good belief replacing the PCM will resolve the whole issue for you too. Seeing as how nearly 100% of all modern vehicles today presenting with this code it is a PCM issue. The odds alone are very much in your favor for it to be the reason. The serpentine belt problem happening like it did is the only reason why I have a shadow of doubt. A lot of different things could have taken place over time because of this. It may have been better for you if the serpentine belt would have just thrown itself off instead. Who knows how long it was actually happening prior to the major symptoms experienced? It could have been occuring for some time, and it may have been demanding unreasonable expectations out of the charging system if it was an ongoing issue that was happening.
PCM came today, installed it, Jeep started right up no problem and ran better!
Took it up and down the road and my ABS light did come on, but did not pull any over voltage codes like I was before the repair. I am no longer pulling the P0622 code (THANK GOD)
with that ABS light on I believe that the huge voltage pull towards the ABS system had just damaged my module. So I’ll go to my local Jeep graveyard and pull on for a decent price unless you guys have a different idea what’s causing that light.
only codes I’m currently pulling are o2 sensor codes and as said earlier I have no catalytic converter. So it has nothing to with (I believe) with the ABS light coming on.
I appreciate everyone’s help and input once again!!
Banned
Joined: Feb 2019
Posts: 1,359
Likes: 169
From: NC
Year: 2004
Model: Grand Cherokee (WJ)
Engine: 4.0
Check for a blown ABS fuse. That could be it. Maybe the module is toasted? It is no big deal really. Unless, you get yourself into a situation where having a working active ABS system would have helped prevent an accident.
The code staying on means your ABS system is not going to activate. This is a real-time code. If there is a problem with the ABS system and it gets fixed, this code will always immediately go off right after fixing whatever is the reason for the ABS light being on. Never should there be a need to try re-booting systems or any computers for this code. Always and never are some of the strongest of imperatives too. There are just a few other reasons outside of having an actual fault of the ABS parts for the ABS light to show. In an emergency situation, the ABS system may still be activated if any of those things were the reason for the ABS light still remaining as illuminated.
You do not need ABS though, and some people prefer it without having ABS. There are for sure situations where ABS will serve to save your tail. I do not believe they can fail you at inspection time with having an ABS light illuminated either.. I am not 100% sure based on the rules in play for in your particular county and state where the Jeep gets registered.
You could take a little piece of black electrical-type non-translucent tape and cover it up if it were annoying for you to see the ABS light on all of the time. I have heard this being done as an alternative instead to fix the ABS CEL hehe!
I am very glad the other code went away for you. This is great news!
The code staying on means your ABS system is not going to activate. This is a real-time code. If there is a problem with the ABS system and it gets fixed, this code will always immediately go off right after fixing whatever is the reason for the ABS light being on. Never should there be a need to try re-booting systems or any computers for this code. Always and never are some of the strongest of imperatives too. There are just a few other reasons outside of having an actual fault of the ABS parts for the ABS light to show. In an emergency situation, the ABS system may still be activated if any of those things were the reason for the ABS light still remaining as illuminated.
You do not need ABS though, and some people prefer it without having ABS. There are for sure situations where ABS will serve to save your tail. I do not believe they can fail you at inspection time with having an ABS light illuminated either.. I am not 100% sure based on the rules in play for in your particular county and state where the Jeep gets registered.
You could take a little piece of black electrical-type non-translucent tape and cover it up if it were annoying for you to see the ABS light on all of the time. I have heard this being done as an alternative instead to fix the ABS CEL hehe!
I am very glad the other code went away for you. This is great news!
Last edited by Noah911; Jan 14, 2020 at 01:48 PM.
Thread Starter
Newbie
Joined: Jan 2020
Posts: 11
Likes: 0
From: Michigan
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0
Check for a blown ABS fuse. That could be it. Maybe the module is toasted? It is no big deal really. Unless, you get yourself into a situation where having a working active ABS system would have helped prevent an accident.
The code staying on means your ABS system is not going to activate. This is a real-time code. If there is a problem with the ABS system and it gets fixed, this code will always immediately go off right after fixing whatever is the reason for the ABS light being on. Never should there be a need to try re-booting systems or any computers for this code. Always and never are some of the strongest of imperatives too. There are just a few other reasons outside of having an actual fault of the ABS parts for the ABS light to show. In an emergency situation, the ABS system may still be activated if any of those things were the reason for the ABS light still remaining as illuminated.
You do not need ABS though, and some people prefer it without having ABS. There are for sure situations where ABS will serve to save your tail. I do not believe they can fail you at inspection time with having an ABS light illuminated either.. I am not 100% sure based on the rules in play for in your particular county and state where the Jeep gets registered.
You could take a little piece of black electrical-type non-translucent tape and cover it up if it were annoying for you to see the ABS light on all of the time. I have heard this being done as an alternative instead to fix the ABS CEL hehe!
I am very glad the other code went away for you. This is great news!
The code staying on means your ABS system is not going to activate. This is a real-time code. If there is a problem with the ABS system and it gets fixed, this code will always immediately go off right after fixing whatever is the reason for the ABS light being on. Never should there be a need to try re-booting systems or any computers for this code. Always and never are some of the strongest of imperatives too. There are just a few other reasons outside of having an actual fault of the ABS parts for the ABS light to show. In an emergency situation, the ABS system may still be activated if any of those things were the reason for the ABS light still remaining as illuminated.
You do not need ABS though, and some people prefer it without having ABS. There are for sure situations where ABS will serve to save your tail. I do not believe they can fail you at inspection time with having an ABS light illuminated either.. I am not 100% sure based on the rules in play for in your particular county and state where the Jeep gets registered.
You could take a little piece of black electrical-type non-translucent tape and cover it up if it were annoying for you to see the ABS light on all of the time. I have heard this being done as an alternative instead to fix the ABS CEL hehe!
I am very glad the other code went away for you. This is great news!
the light tends to come on after a few brake presses, not as soon as I start the jeep. Where I’m at in MI most of the roads are covered in ice, driveway included. Is it just realizing that something is wrong when hitting the brakes on ice thus sending the failure light on?
if it is the module for sure which it looks to be because upon checking the fuse, which was the first thing I did it was completely fine. I plan on going to one of the local Jeep graveyards and yanking an ABS module out of one of those Cherokees for the sake of comfort.
I definitely still need to put more miles on it still to see if any more codes come up buy after the two miles I took it today I’m a little more comfortable.
Regardless, progress is progress and it’s better than it sitting on my driveway wasting away!
Banned
Joined: Feb 2019
Posts: 1,359
Likes: 169
From: NC
Year: 2004
Model: Grand Cherokee (WJ)
Engine: 4.0
Here is what I would do if it were me. I would drive the Jeep someplace with a wide open space. Making sure there was no real chance of accidentally hitting something. I would definitely try to do this away from and off to the side of any street or roads. Definitely not near to any traffic.
I would get the Jeep up to speed some while driving on slick stuff like icy snow or wet saturated pavement. Then, slam on the brakes for a few.. I would want to try and activate the ABS system in order to see wether or not it will work how it normally should under those conditions.
I now drive one of those new TRD Tacomas, and I have been putting it through its paces plenty on icy snow covered dirt backroads. At times, I was probably activating this trucks ABS system at least 40 - 50 times a day every day while I was out running in the field. I had a lot of ground to cover and would gun it from a stop and slide right into position as I went along.. There was hardly any if ever anybody else around, and I could see for miles though.
Since you live where it snows you probably have perfect conditions right now to test for ABS activation. I would want to see if it works or not, in order to satisfy my own curiosity.
Since it is a real-time code. It does make some sense that there may possibly be a parameter needing set when you first drive, as the system does its checks?
I would get the Jeep up to speed some while driving on slick stuff like icy snow or wet saturated pavement. Then, slam on the brakes for a few.. I would want to try and activate the ABS system in order to see wether or not it will work how it normally should under those conditions.
I now drive one of those new TRD Tacomas, and I have been putting it through its paces plenty on icy snow covered dirt backroads. At times, I was probably activating this trucks ABS system at least 40 - 50 times a day every day while I was out running in the field. I had a lot of ground to cover and would gun it from a stop and slide right into position as I went along.. There was hardly any if ever anybody else around, and I could see for miles though.
Since you live where it snows you probably have perfect conditions right now to test for ABS activation. I would want to see if it works or not, in order to satisfy my own curiosity.
Since it is a real-time code. It does make some sense that there may possibly be a parameter needing set when you first drive, as the system does its checks?
Old fart with a wrench
Joined: Nov 2010
Posts: 14,398
Likes: 741
From: Manlius, east of Syracuse, NY
Year: 2000 XJ Sport & WJ Laredo
Model: Grand Cherokee (WJ)
Engine: 4.0L
I'd like to add that if the light only comes on after brake activation, it's entirely possible it's just a wheel sensor that's not reading the wheel speed. The back of the spindle stub where the u-joint is has notches that the sensor counts to determine that wheel's speed. If the notches are rusted they may be interfering with that reading. The ABS system gets activated when the wheel speeds differ from each other or vehicle speed.
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