My girlfriend's 2005 GC started saying "Service 4WD System" and "Service Elec Brake System" today on the message center. They are not always present, and when one message goes away, they both disappear. I tried to put the truck in 4LO, works just fine and everything feels fine.

I am planning on taking it in to Jeep on Monday for service, but any ideas on what could be going on? Seems like these two should be unrelated unless it is a computer issue.

It got an oil change at the dealership, including a tire rotation, about 300 miles ago...could an ABS sensor have been damaged or accidentally disconnected?

Any other ideas of what could be going on?

Mike

Probably unrelated, but our complex has a bunch of speed bumps and the first time the message sturned on was on while it was right after going over the bumps...

Sounds like it might be electrical

i get the "service AWD system" message about once a day, but it only flashes for a split second. i took it in to service today. i can't imagine anything is wrong with the AWD system, and i hope it is only a glitch.

My girlfriend's 2005 GC started saying "Service 4WD System" and "Service Elec Brake System" today on the message center. They are not always present, and when one message goes away, they both disappear. I tried to put the truck in 4LO, works just fine and everything feels fine.

I am planning on taking it in to Jeep on Monday for service, but any ideas on what could be going on? Seems like these two should be unrelated unless it is a computer issue.

It got an oil change at the dealership, including a tire rotation, about 300 miles ago...could an ABS sensor have been damaged or accidentally disconnected?

Any other ideas of what could be going on?

Mike

Probably unrelated, but our complex has a bunch of speed bumps and the first time the message sturned on was on while it was right after going over the bumps...


I had this same problem after putting in my Cold Air Kit. Eventually the message went away. It worried me at first tho. These computers are very very smart, and sometimes they just need a little time to fix themselves.

It is a glitch. There is a TCB to fix it...

Ok so we took the Jeep in and they said that the computer had to be reflashed with new software. Unfortunately this took the dealership all day to do. When we picked it up, after the service dept was closed, the messages popped up immediately.

Just one new thing, now we also have the check engine light on as well.

Not quite sure whats going on here, I thought it may be an ABS sensor that was damaged because that would relate to the original messages. However this new one is scary.

Back to Jeep tomorrow...will keep everyone posted.

Mike

Sorry for the extremely late reply to this, but if anyone else runs into this problem it is caused by a failed brake light switch at the base of the brake pedal. Although the brake lights continue to work normally, there is a position sensor that is linked to the transmission and 4WD system. I have had mine fail twice now and each dealership has said that they have never seen a failure before. Both times it was ~$100 for labor / diagnostics and ~$100 for the part. The tech said the install is very straightforward so I should just do it on my own next time. BTW the part has a 12 month warranty and the second time it failed was the 13th month after the first replacement...go figure : )

Hope this helps others!!

Def sounds like some sort of electrical short/problem.....GL with fixing it!

Ya its an electrical problem.

being that I just got my. Jeep I don't know all to much about it as of yet,, the tc button since it stays on what difference does it make off?

4 wheel drive low? we dont have that

ohh alright thanks im sure ill figure everything out quickly as soon as i start driving it and get my liscense

Sorry for the extremely late reply to this, but if anyone else runs into this problem it is caused by a failed brake light switch at the base of the brake pedal. Although the brake lights continue to work normally, there is a position sensor that is linked to the transmission and 4WD system. I have had mine fail twice now and each dealership has said that they have never seen a failure before. Both times it was ~$100 for labor / diagnostics and ~$100 for the part. The tech said the install is very straightforward so I should just do it on my own next time. BTW the part has a 12 month warranty and the second time it failed was the 13th month after the first replacement...go figure : )

Hope this helps others!!

thanks alot

do i need to change the switch or check the brake lights??

So our Jeep (2005 Grand Cherokee V8 AWD) likes to burn through these switches like nobody's business. I just had to purchase #4 and installed it on my own. It only cost $10 from the Jeep dealership and is called the "brake light switch." When you pick it up make sure it has a square mount just above the plunger and not a wing shaped one as they sent me home with the wrong one the first time.

Installation is a snap, two phillip's screws removes the kick cover under the dash. Then grab the old brake light switch near the pedal and rotate it counter-clockwise about 30 degrees (it will click). It should then just pop out of its mount. The cable harness has a zip tie clip holding the excess cable out of the way; I removed this clip from its mount to give me enough room to pry out the connector.

Next plug the new switch into the connector, push the brake pedal in a bit to keep it out of the way. Put it into the mount and rotate it 30 degrees clockwise to secure it. Be sure to put the cable tie back to keep the wires in their place. Finally put the kick guard back in place with two phillip's screws.

NOTE: when you let the pedal go and it hits the new switch, it will make a bad "crunch" sound. This is OK as I figured out by dissecting the old switch. It is just an adjustment of sorts for your brake pedal.

FYI if you see these two error messages "Service elec brake system" and "Service 4wd system" there are several possible causes of the failure.

* Faulty brake light switch: This has been my failure each of the four times; note that the brake lights continue to work normally when this switch fails. There are three sets of contacts inside the switch; two normally open and one normally closed. One of the additional sets not related to the brake lights must be failing.

* Faulty, dislodged, or disconnected ABS sensor at one of the wheels. If you recently had a service that had the wheels off (brake service, tire rotation, etc) start looking here.

* ECU firmware update. This is the first thing the dealer tried on ours, but it did not help on our Jeep.

* Transmission / Transfer Case sensor failure.

* Other: there are numerous components, sensors, cables, connectors, etc in this Jeep and it could be caused by something no listed above.

WTF?? I had a similar issuean hour ago at the gym. Someone came in and told me that my tailights were on and bright, as if I was pressing on brake pedal. Remote start wasn't working, I got in and started the car then the engine was running and it stayed on even as I turned key off and pulled it out!!! I tried to engage into drive it wouldn't work I revved it a bit and it didn't cut off, the "SERVICE AWD SYSTEM" or whatever it says was flashing on the dash along with a BUNCH of other lights like the ESP etc..etc..

I ended up pulling the big yellow IOD fuse and it shut the car off. I luckily had my predator in the glove box so I put the stock tune back in and used diagnostics menu to clear the code. I just got home and searched only to find this thread with similar things. WTF?!?!?! Is it my brake switch too?? I have LED tails, does that matter?