tico1447

In February I bought a 2006 Grand Cherokee, Herman, but he has a tendency to act up.

When he is cold and I make a turn (right or left) under acceleration, I hear a tone, lose power and the engine and traction control icons blinks. Then a few seconds later they all go out and the Jeep runs fine. Two trips to the dealer, two to my transmission shop and two to my mechanic and it still acts up. The dealer ran their computer on it twice and even "flashed" the computer which seemed to help for a few days.

Now a new problem popped up yesterday. At idle at a light when the car has reached operating temperature, the oil light begins to blink. So into the Firestone dealer for an oil change and new oil sending unit. About ten minutes away from the Firestone and it started again. If I give it just a little throttle, the light goes out. And I have let it sit like this for a few minutes with the radio off and windows open and the engine sounds fine, no tapping or any noise that would indicate there is an oiling issue. If this were a 1970s or '80 car I would just raise the idle, but...........

I really love this Jeep but I have had enough of computer operated vehicles. Herman is about to find a new owner!

Does anyone have any ideas as to what the heck is going on?

Thanks
Ed

dave1123

Yeah...well...you're going to have to go WAY back to find a vehicle that ISN'T computer controlled in some respect. Jeeps aren't too bad back as far as '94 or so and the '99 to '04 Grand Cherokees are okay, but once they started getting things like traction control and automatic terrain control, they get complicated. Even stuff like dual zone climate control and memory mirrors are a pain to fix.

My '00 WJ is the newest vehicle I'll ever own because I can still understand the systems and repair it easily enough, but it's a base model without all that garbage they call luxury. It doesn't have automatic headlights, power seats, and has a standard heater. It also has a simple transfer case that requires a shift lever to operate. It has the 4.0 straight 6 which is jeep's most reliable engine and a complete set of gauges. When it finally dies, I'll probably go get another one the same age.

Go get yourself a Mopar oil pressure sensor. A lot of aftermarket sensors are not accurate.

tico1447

A new wrinkle on Herman's peculiar operation.

The oil light only comes on after the vehicle is warm and I have run the A/C. If I do no run the A/C, the oil light never comes on. So it is just another nuisance that I will have to live with. Now I am not a computer wizard but am very logical. To that end it would seem the problems I am encountering are indeed computer related. If it were my desktop/laptop/tablet that this was happening to, I'd run my anti virus software. But I doubt there is anything that can be done to an automotive computer once it has been corrupted. The dealer did "flash" the computer and it seemed to work well for three or four days before it started to act up again. New PCMs are $600.00 and up from the dealers and used or "rebuilt" ones are $250.00 and up. And what exactly do they do to "rebuild" a PCM? Clean it?

Later!
Ed

dave1123

Basically clean it, put new capacitors in it, test the semiconductor chips, and clear the memory. Then they install a basic "run" program. When the dealer "flashed" the PCM, he refreshed the run program. Of course, that did not fix the problem what ever it was/is. It took a couple of days for the PCM to alter this program with incoming data from the engine and body module. These cars work on a CAN/BUS system where all the different modules talk to one another.

I have an intermittent ABS light that comes on for no reason. They tell me the PCM runs a diagnostic test of all systems and sets a light if it's not happy with this test. My ABS works perfectly even when the light is on but it will sometime pop on even when I'm sitting idling and not touching anything! If I shut the engine off and wait about 5 minutes, it will be off on the restart. I'm about to remove the bulb! I'll still get the "ding" when it sets, however.

tico1447

Thanks Dave for the reply. It makes things a bit clearer and understandable. It sounds like the only thing to do is to start replacing sensors until the problem goes away. But at this time, I think it is time for Herman to go. The car is absolutely beautiful and when it isn't acting up, it drives really well. But since the A/C seems to make it run bad, it just isn't feasible to drive around with the windows down. Oh, and he just did another dumb thing. I was re-caulking the new shower door I put in (who knew silicone has a shelf life in the tube?) on Saturday and all of a sudden I hear a horn and look outside and there he is is honking his horn. I run out and open the door and put the key and start it. Nothing! So I lock and unlock the doors. Nothing! So I open the hood and open the garage door to get a wrench to disconnect the battery and just as I reach in, the honking stops! Now here is where it really gets atrange. The windows were down a bit to keep it from getting too hot. It has begun to drizzle when the horn went off. Could this thing have a rain alarm?

Thanks again.
Ed

dave1123

I seriously doubt it, but moisture may have tripped one of the door switches and set off the security system. It probably stopped honking because the alarm "timed out". Have you started it since this happened?

tico1447

Yes. But since I had disconnected the battery after the alarm stopped, I pulled the three connectors off of the computer and cleaned two ground connections beside the battery. I started it and here's where it gets strange. No oil light, no traction control light and I was running the A/C. So of course I am thinking that cleaning the connections fixed every thing (with my fingers crossed). And this morning on my way to get parts for my other car, it started acting just like it always does, lose of power, blinking traction control light and blinking engine light. After a few minutes of driving, the car ran fine and the engine icon went out.

And since the sensors talk to each other as you stated, I doubt changing the computer will do any good. And changing sensors won't do any good either unless I wanted to spend a small fortune on that process. Anybody want to buy a really clean '06 Grand Cherokee with computer issues?

Later!
Ed

dave1123

It's not the sensors that talk to one another, it's the modules, as in PCM, Body Control Module, Transmission Control Module, ABS Module, Traction Control Module, and anything else that has computing power. For example, the body control module detects a burnt out tail light and informs the PCM, the PCM informs the VIC and displays it on the screen. Or maybe it's directly from the body module to the VIC, IDK. Most of the sensors are used for sending info to the PCM for fuel trim and ignition timing. Where it get complicated is when to PCM detects a drop in engine rpms, a drop in vacuum and vehicle speed, and an increase in throttle opening, it tells the transmission to downshift. Your problem is probably simple, but finding it is a killer.

tico1447

Thanks Dave. You have given me more information in your replies than the dealer does. Today it did as it usally does but today, the engine icon stayed on so there is now a stored code so I will see if the dealer can take it on Monday and see if they can track down the source. Otherwise I think it is time for the Jeep to go. It is just too unreliable to try to drive.

Thanks again for all of your input.

Later!
Ed

dave1123

If you want my opinion, dump it for an older model in good shape. The '99 to '04 WJ's are a lot less complicated.

tico1447

I dropped the Jeep off at the dealers Monday evening. Called late Tuesday to see what they found out. They said it had the misfire code in and the tech sent an e-mail to Star, the Chrysler tech hot line to get their input. They called me yesterday and said the Star folks told them to clean the fuel system because it has water in it. They had to order the cleaner and it will be done today. $248.00 for that and the diagnosis. They might have to drop the tank and flush it as well. Now I am not up on the latest computer technology regarding cars but I have done a restoration or four or five including and engine rebuild here and there. This might take care of the loss of power on occasion but I doubt it will be found to be the cause of the traction control problem when the car is cold. I'll let you know how it works out.

Later!
Ed

tico1447

Cleaning the fuel system didn't help. So they said it might have a blown head gasket. The tech tested and found out that wasn't blown after all. So then they said they were going to put in an O2 sensor, (hey didn't say which one) and if that works, then that was the problem. if not, they would put the old one back in. Tomorrow marks two weeks they have had the car.

I might take a day off and sit down with the service manuals to see if there is a trouble shooting chart for this problem. I also want to see if the books have resistance ratings for the myriad of sensors in this car. I am out of suggestions and feel the car needs to go. I seriously doubt there are any real technicians out there any more, just a bunch of folks that plug a computer into a car and wait for the computer to tell them which part to change.

Later!
Ed

dave1123

Yes, the diagnostic part of the PCM only goes so far, then it's up to the technician to figure out what to look at. Most of today's techs are just glorified parts changers. Bottom line, they are paid by the manhour. They do, however, have specialized scanners that can read separate modules, if they care to.

tico1447

Well, I picked up Herman Friday. So two and a half weeks and $500.23 later he is running pretty good (knock on wood). They ran the diagnostics and the computer told them nothing so they contacted STAR (excuse the spelling, it is the troubleshooting section at Chrysler) and they said to clean the fuel system which took four days since they had to order the kit. They also said they might have to drop the tank to clean out the water in there! What? They didn't drop the tank but the cleaning system didn't solve the problems so they again called Star and again had to wait two days to hear back from them. Now they said it sounded like a blown head gasket. That required a test drive with computer hooked up. That test showed no problems. Again, a wait for Star to call back. Now they said to change the O2 sensors. But they didn't have them in stock. Another three days passes and then they called Thursday to say the car was done and after two days of test drives everything was OK and the car has new pep. So I picked it up and so far it runs OK but it doesn't have any more pep. If anything it is kind of sluggish. But we can't have it all, can we?

Later!
Ed

CR-Snow

If your warning lights are back to functioning properly, I'd say you're clear to put that thing up for sale with a clear conscience. Sounds like a head ache and a half. Good luck