OBD Codes P0700 and U1146-Lost Communication With External Memory
Hi all - first post here but I wanted to share my experience in hope that someone can benefit. I'll try to keep it as brief as possible but with as much detail as possible. 2009 Caliber SXT 2.0 FWD, infamous CVT transmission with 118,000mi at current. Please forgive me if this should be posted elsewhere.
Last summer I was driving home from Chicago -> Pittsburgh and after about 4 hours at 75MPH in 90 degree weather, I had the "Transmission Temperature Indicator" light come on. I had never seen that before so I had the wife pull out the OM and it states, "During sustained high speed driving on hot days, the automatic transmission oil may become too hot. If this happens, the transmission overheat indicator light will come on and the vehicle will slow slightly until the automatic transmission cools down enough to allow a return to the requested speed."
I thought to myself, how stupid! Seems like poor engineering to me, if my car can't keep itself cool while driving. This is an actual thing that can happen and isn't indicative of something gone wrong?! But, the long trip was infrequent and wasn't much of a concern. We stopped to have lunch; the light was off when we started up again and we continued on. The light came on one or two more times during the trip. Because there was no instruction to pull over or cease opening the vehicle, we pressed on and made it home, albeit a little slower than we'd have hoped for.
The car ran fine the following day, weeks, and months. I often make Cleveland <-> Pittsburgh trips for work, and this spring I noticed a whine coming from the transmission while on such a trip. I was about 90 minutes into the drive and it was another hot day so I figured that must be some kind of cooling mechanism built in to the transmission, since I recalled hearing that noise shortly before the over temp light came on the previous year.
Well, as luck would have it, the over temp light came on shortly thereafter. I continued home at less-than-desirable speeds. At this point I figure I should probably check the transmission fluid level, only do discover the tube was capped with no dipstick, and a tag that says, "Dealer Service Only." This was quite a shock! Chrysler doesn't want me checking my own fluid level? I called my local dealership. They quoted a $98 fee to check the fluid level, and $300 for a drain and fill. Again, I was quite shocked at the cost. I had just paid less than half of that to have the transmission fluid changed in my 4.7 liter 4x4 Jeep Commander! And, I could even check the fluid level myself! At any rate, I decided against either action. The logic here was, I hadn't received any warning lights or odd behavior other than a transmission "whine" followed shortly thereafter by an over temp light, which my owner’s manual doesn't indicate anything is out of the ordinary.
Three weeks pass and we set off on another trip to visit my in-laws in Chicago. Now, this is the point where I made a decision in which I ended up regretting. I decided to take the Caliber, knowing it had been temperamental on long trips at highway speeds. The Jeep Commander is a much more comfortable and quiet ride (love that vehicle) but at a cost of 10 less miles per gallon, which adds up on an 8 hour drive.
About 150 miles into this trip, the over temp light comes on again. We decide to NOT turn around to get the Jeep, but to find the nearest car rental and continue on. We take the Sandusky OH exit and drive about 8 miles to the Enterprise Rent-A-Car, rented a vehicle, transferred over all our luggage and such, and continued on. The thought was, 4 days later, the car will be nice and cool. It should be able to get us home, or at least within our AAA 100 mile towing limit.
Following a fun 4[SUP]th[/SUP] of July weekend with the in-laws, we return to the vehicle to find it starts up without issue, sans over temp light as I had expected. Great! We transfer our belongings back into the Caliber, return the rental, and we’re on our way. Almost. As soon as I put the car into Drive, the check engine light came on and the car officially entered limp mode, which did not allow the RPMs to go above 2k.
Previously, the over temp light caused a “higher than usual” RPM condition, which I thought was limp mode, but alas, was not. It would take the RPMs from a nice 2.5k highway cruise, to a solid 4k, engine whirring transmission whining cacophony that could only trigger the famous Loaded Weapon quote (here, if you’re too young http://www.wpol.com/scotty.wav
). Fear of running the engine at redline was the only factor that forced a slowdown.
Needless to say we weren’t even going to attempt a drive home. I’ll spare everyone the details of the ridiculous level of customer service that AAA provided to their “plus” tier long-time member (me) by saying, we left the car in the Enterprise lot, rented another car to get home, and I drove the Jeep up the next day with a rented U-Haul car dolly and brought it home myself.
On the way, I pulled into the friendly neighborhood Auto Zone and asked them to read me the codes. The technician connected the reader and after a few fumbled button presses became wide-eyed and explained there were a grand total of 18 codes, and all were transmission related. After a long weekend and a long drive, I was done dealing with it. Drove it to the dealer and dropped it off.
After a few days they called me said told me to come get it. They had cleared the codes, drove the car “all around (which ended up being 6 miles according to the odometer) and couldn’t get any errors to return. The car was well again. I got a ride there the next morning, and after paying their $100 diagnostic fee the car was mine.
That is, until I started it up and noticed that the check engine light was on. I went back into the dealer’s service department and informed them of my discovery. He was surprised to hear the CEL came back on. I told him my ride had already left so I’d appreciate if they could take another look at it right there, which they agreed to do.
Twenty minutes later they informed me that the TCM was fried, and that they could order a new one, have it fixed by tomorrow for only $491. I was shocked at the cost, but frankly was tired of dealing with this and wanted it to just be over, so I agreed and got a ride to into work.
I didn’t take long until I was second guessing their diagnosis. From what I read on this forum and other internet sites, wiring is often an issue. That seemed to align with the symptoms, sometimes it worked, and sometimes it didn’t. Seems to me a “fried” TCM would not sometimes work. I was so confident in this that I got a ride back to the dealer after work, told them I wanted to look the car over myself first, and drove it home in limp mode.
I first checked the connections into the TCM and wiring under the dash. All looked pristine. The wiring was firmly connected into the TCM, and inspecting the leads showed no sign of corrosion. Next, I removed the driver’s side wheel and plastic wheel well trim, exposing the main wiring bundle coming from the cabin, over the wheel well, and the wiring into the side of the transmission. Again, I inspected every inch and found no kinks, tears, breaks, etc. All looked to be in great condition. The harness into the side of the transmission looked great, too.
Frustrated for not finding what I suspected would be a smoking gun, I drove to the auto parts store and picked up my own OBD reader. This is where I saw the P0700 and U1146. From what I’ve read, the P0700 is a generic code to signal the MIL. The U1146 was the root of my problem. The Chrysler Service Manual states “The first time the vehicle is started, the Transmission Control Module (TCM) receives hydraulic calibration data from an external EEPROM (located in the transmission) and stores this information in the EEPROM of the TCM. If the TCM can not read the external EEPROM in the transmission this DTC will set. It takes two consecutive failures to turn on the MIL.”
The Chrysler Service Manual lists the following possible causes for this, along with troubleshooting steps, in the following order:
- (T327) DATA IN/OUT SELECT CIRCUIT SHORT TO VOLTAGE
- (T313) CHIP SELECT CIRCUIT SHORT TO VOLTAGE
- (T302) CLOCK SELECT CIRCUIT SHORT TO VOLTAGE
- (T327) DATA IN/OUT SELECT CIRCUIT OPEN
- (T302) CLOCK SELECT CIRCUIT OPEN
- (T302) CLOCK SELECT CIRCUIT SHORT TO GROUND
- (T327) DATA IN/OUT SELECT CIRCUIT SHORT TO GROUND
- INTERNAL TRANSMISSION
- TRANSMISSION CONTROL MODULE
They all involved testing the circuits with a test meter. I didn’t have a test meter, and was pretty confident that the wiring was good. That only left the internal transmission, or the TCM, which they recommended be replaced. Being that was the lesser of the two costs, I put the car back together and drove it back to the dealership.
They called the next day and told me they got the new PCM installed and now the car will barely move. They think it’s defective and have ordered another one and that they’d call me again tomorrow. The next day they call and tell me the 2[SUP]nd[/SUP] replacement PCM won’t even program, so it’s gotta be the transmission. (Side note: Seems odd that they could determine it was the transmission, based on different behavior from two TCMs. You’d think if it was the transmission, the TCM behavior would be identical, but I’m not the expert here.) It’s hard to tell how accurate that is, since the tech probably talks techie to the service manager who then tries to comprehend it and then has to turn around and interpret it for the customer.
So, if you’ve made it this far you must at least be slightly interested in my story. I won’t leave you hanging so I’ll go ahead and tell you that I told them to replace the transmission. At least the replacement has a 3yr/100k warranty. I definitely don’t want a car payment, and anything I could pay cash for likely wouldn’t have a warranty. At least I knew the history of this car (owned since 18k miles) and believe it’s pretty solid otherwise. Oh, and the cost is $4,000.00 but the service manager was able to get the price down to $3,075. Still seems ridiculously high to me, but I’m over it. Lesson learned, here.
In summary, if I knew all of this before I began having these problems I would’ve traded in that Caliber at the first over temp light last summer. In retrospect it was just a warning sign of worse things to come. Now that you know all this, hopefully before you’ve experienced any CVT transmission issues, you can make more of an educated decision than I was able to. I’m not saying every over temp transmission is soon to catastrophically fail or every U1146 code is a failed transmission. This is just one man’s experience and I hope it helps.
If you really want to keep reading, while at the dodge dealership, one of the salesman made his best effort to get me into one of those new Dodge Darts. It doesn't have a CVT, but it's unlikely I'll buy another Dodge.