Replacing engine computer

Tiny
DINDLE24
  • MEMBER
  • 1999 JEEP CHEROKEE
  • V8
  • 4WD
  • AUTOMATIC
  • 170,000 MILES
What is the level of difficulty in changing an engine computer and are there special tools needed?
Do you
have the same problem?
Yes
No
Thursday, June 26th, 2008 AT 6:24 PM

44 Replies

Tiny
OBXAUTOMEDIC
  • MECHANIC
  • 3,711 POSTS
Level of difficulty is simple, no special tools, the only thing is just like with your home computer be ware of static electricity.

Location if you don't already know is left side front of engine compartment.
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:20 PM
Tiny
412KIMBO
  • MEMBER
  • 1 POST
  • 1999 JEEP CHEROKEE
  • V8
  • AWD
  • AUTOMATIC
  • 119,000 MILES
I am having this issue when I accelerate uphill it seems to happen mostly my overhead console flashes liftgate open and computer tries locking the doors continually. I have been having problems with stalling but a new throttle position sensor fixed it. I still have idling issues it idles rough as can be. Do u believe the problems are linked somewhere like the PCM? Also if this helps my door locks automatically lock, but after being locked it would continue to lock itself. I am utterly confused. There is a total lack of engine power sound like it is running fine just lacks the gitty up i'm used too with a 4.7
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:22 PM (Merged)
Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
I'm going to break this down b/c I don't see your problems being related. I'm assuming the "liftgate open" light problem is intermitent. I would try liberally spraying the latch assemblies down with some type of spray lubricant and working the hatch and doors a few times. The ajar switches are inside the doors attached to the latches and are prone to sticking. I don't recomend using WD-40 or any other type of "rust breaker" for this. They are corrosive and can make the problem worse.
On your door locks. My thought is you have a lock/unlock switch that is defective and from body vibration may be trying to lock itself. As a rule, these switches are pretty sensitive.
Your performance issue. You can have a shop hook the vehicle up to a perfornance diagnostic unit, but I think you'll find it's just the "nature of the beast". They are not known for excessive horsepower. Hope this helps.
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:22 PM (Merged)
Tiny
SKYLYNN01
  • MEMBER
  • 1 POST
  • 1999 JEEP CHEROKEE
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 163,894 MILES
I went and got my jeep inpected and they said that re flash or replace on board computer. What does that mean? And what is the price ranges?
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:22 PM (Merged)
Tiny
CRZYDRVR
  • MEMBER
  • 432 POSTS
I believe they are talking about the engine computer. It is located behind the drivers side headlight next to the air filter housing. Your better bet would to try to locate a used one. Around here they are in the range of $50- $100
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:22 PM (Merged)
Tiny
CRISTABERTRAND
  • MEMBER
  • 1 POST
  • 1999 JEEP CHEROKEE
  • V8
  • 2WD
  • AUTOMATIC
  • 172,500 MILES
I hit a bump the other day and my check engine light came on. I unplugged my battery to rest it. The next day I tried to crank it, it cranks but has no spark and does not turn over. None of my gauges register, but my lights work? I heard it could be my rollover button? But I am not sure of that, or my ASD relay, I unhooked then rehooked it but still nothing. Under my odemeter it says No Bus? All my fuses appear to be ok? Can u help me?

Lady in distress
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:22 PM (Merged)
Tiny
JNOVACK
  • MECHANIC
  • 723 POSTS
It could be eather one or both or even one of the grounds on the jeep check all the grounds mostly the one under jeep that goes from frame to the exhaust to the trans this is one wire that goes to all 3 but would like to know code for check engine
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:22 PM (Merged)
Tiny
NATHAN HAMMOND
  • MEMBER
  • 1 POST
  • 1998 JEEP CHEROKEE
  • 4.0L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 160,000 MILES
Cannot seem to find the PCM on my vehicle. Looking into it possibly heating up and causing misfires and going into "limp home mode" constantly.
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:22 PM (Merged)
Tiny
JIS001
  • MECHANIC
  • 3,408 POSTS
Here is the location on the PCM engine control module in the diagrams below that also explain how to replace it. Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:22 PM (Merged)
Tiny
CHRIS417
  • MEMBER
  • 3 POSTS
  • 1998 JEEP CHEROKEE
  • 24,000 MILES
I just bought my 1998 jeep cherokee 4.0 automatic about 2 weeks ago, was running fine for the first week and now its running like garbage, the CEL came on and I got it checked out. The code was PO171. The truck has 240k on the body and the previous owner said the motor was replaced and now this current one supposevely has around 80k on it. 2 days ago I did a full mopar tuneup, cap rotar plugs wires air filter and I reset the ECU. The truck was running great for about 15 hours and then on day 2 it was back to how it used to be. Running really rough. At idle my truck clanks around like it wants to stall but the RPMs are normal. The truck has a very strong fuel smell like it is running very rich and also the MPG are wayyy down. Any help on what I should do? This is my only veichle. Thankyouu
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:23 PM (Merged)
Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
Is the engine light on again? If so is it the same code? Are you up to testing a couple of things? Did you replace the fuel filter too? You replaced plugs and wires correct? You will need a digital multi meter to run some test ok.
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:23 PM (Merged)
Tiny
CHRIS417
  • MEMBER
  • 3 POSTS
Yes check engine light is back on, it is the same code, I cleaned my throttle body today nd blew out all the plugs attached. Still runs the same. I did not replace the fuel filter, no idea how to even check it. And yes I did put in a new cap plugs and wires during the tune up, my dad is an electrician and works on cars sometimes so I am sure he has a multi meter.
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:23 PM (Merged)
Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
I think I would start with the fuel filter it just infront of the gas tank. P0171 is lean condition bank 1 and this can be a lack of fuel by having a plugged fuel filter so thats why I say start there and you have never replaced it so it won't hurt to do it anyway and eliminate that as the cause ok. Once that is done see how it runs and let me know and we will go from there.
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:23 PM (Merged)
Tiny
CHRIS417
  • MEMBER
  • 3 POSTS
1997-2001 cherokees have the fulter inside the tank, its part of the pump assembly. Cant afford to replace the pump or dump out 16 gallons of fuel with no where to put it all. Also the truck runs like garbage till I reset the ecu, once I reset it and start the truck back up it seem to run good for a few hours and then the next day its back to square one. That makes me feel like its an o2 sensor, I also checked all of my grounds and all the fuses to make shure the fuel pump fuse wasnt blown and its still basically new
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:23 PM (Merged)
Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
You have a standard cherokee or grand? On the grand cherokee it is just infront of the tank as I have 99 grand cherokee, on the standard cherokee it don't have an inline filter. With that yes it could be an o2 sensor. You don't have any vacuum leaks do you? If not then I will walk you though on testing the o2 if you want.
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:23 PM (Merged)
Tiny
2CP-ARCHIVES
  • MEMBER
  • 4,544 POSTS
  • 1998 JEEP CHEROKEE
  • 150,000 MILES
My oem brain needs replaced, can I buy a used one or does it need to be new
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:23 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,689 POSTS
A used one is a bad idea if your vehicle does not have the factory anti-theft system. If it does, you can use any computer. If the one you get isn't programmed for anti-theft, it will learn that from the Body Computer the first time you turn on the ignition switch, then work normally. If your vehicle doesn't have it but the used computer you get does, it will teach that programming to the Body Computer. At that point the engine won't start because both computers will be waiting for a disarm signal that is never coming. At that point you will need to replace both computers at the same time with ones without anti-theft programming.
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:23 PM (Merged)
Tiny
WALTKNY
  • MEMBER
  • 1 POST
  • 1997 JEEP CHEROKEE
Computer problem
1997 Jeep Cherokee 6 cyl Four Wheel Drive Automatic

i had to buy a used PCM for my 97 cherokee. Do I have to get it programed from the dealer or can I install it? And how? Just to be safe! It is out of a 97 and was tested and it was good. Please help ive put way to much into this jeep for just a work truck. Im hoping it will make me the $$$ for another one fer a TOY!
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:23 PM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,758 POSTS
You are really rolling the dice there. Just because it came out of a 97 doesn't mean it's even the right one for your truck and it definitely has to be programmed before use.
Was this
answer
helpful?
Yes
No
+2
Tuesday, August 11th, 2020 AT 6:23 PM (Merged)
Tiny
SKY.ROCKET123
  • MEMBER
  • 2 POSTS
  • 1997 JEEP CHEROKEE
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 170,000 MILES
Changed it twice ' car races and stall. Garage said the ecm computor is the problem. I go to from 1997 cluckers and one ran for 3 weeks then statred to do the same. The next one just raced. Am I doing some wrong. Does it have to be installled a special way I took the terminal off not to spike it ' three computer al know good? I match the computers what do you think am I doing something. Do they loose there info. Are they reprogramable? Help
thanks
Was this
answer
helpful?
Yes
No
Tuesday, August 11th, 2020 AT 6:23 PM (Merged)

Please login or register to post a reply.

Sponsored links