Saturday, January 27, 2007

Mechanical update...

We are at the Elks lodge in Sierra Vista (map), visiting some friends here for the weekend.

Thursday afternoon found us at W. W. Williams in Tucson. They were able to get to us within an hour or so, and a transmission tech came out with a code reader to diagnose the unit. Unfortunately, after digging out the diagnostic connector and plugging the reader in, the reader could not find any signal from the transmission computer (ECM).

I am only a little surprised by this. We had no transmission diagnostic connector at all when we got the coach, at least none that we could ever find. During the conversion process at Infinity Coach, we rerouted some of the harnesses for the transmission, including relocating the ECM, and Infinity added the diagnostic connector. It is unclear, however, that the connector was ever tested by connecting a code reader. So add to my list of projects tracing the four wires in the connector back to the rest of the harness to see why no signal is available.

The diagnostic thus unavailable, the tech opted to go with us on a test drive instead. He only needed one run around the block to determine that the transmission was fine (whew) and that the problem was actually a momentary drop-out of engine power. He had the service manager ride around the block with us to confirm this. The service manager also sniffed the tranny fluid and informed me that what I was smelling is normal for (and unique to) TranSynd fluid. So out came an engine tech for another ride around the block.

The engine diagnostic connector works fine, and the test drive with the engine tech aboard and an engine code reader connected revealed that the throttle position indication was dropping out during acceleration. The indication on his code reader was very clear, whereas one has to really be staring at the display on our built-in reader, which is perhaps why we did not detect this ourselves, even though we thought to look there several times.

That took us through the end of the day, and we parked for the night in their customer parking area outside the gate. I spent a couple hours yanking out the cables and connectors for our throttle pedal, and testing it with a meter. The Throttle Position Sensor tested good, which seemed to suggest the problem lay elsewhere. In an incredible stroke of luck, however, they had another coach in the shop which they were converting to DDEC-II, which is the same engine control system we have on Odyssey, and they already had an entire throttle pedal assembly on order for that project, scheduled to arrive Friday. Now DDEC-II is an ancient system, and no shop stocks something like an entire throttle assembly for this system, so this lucky coincidence really saved us a lot of time and money in the diagnostic process.

Yesterday morning they handed me the new pedal assembly and Louise and I installed it temporarily for a test. The engine tech came aboard with his code reader, and we went around the block several times, with nary a hint of the problem. I couldn't understand how the old pedal tested good, yet the new one seemed to fix the problem, but we were willing to accept it as luck. So we bought the pedal for $230, finished installing it in a more permanent manner, paid our shop bill, and headed out to find a much-needed laundromat.

With all the lead-up, I'm sure by now you can guess that the problem came back almost immediately after we pulled out of the shop driveway. The laundromat we were headed to turned out to be defunct anyway, so we called the shop, drove back, swapped back to our old throttle pedal, returned the pedal we bought, and discussed next steps. The next step, it turns out, is to replace the ECM, which, on Odyssey, is a several hour project owing to the number of items that need to be removed first before the ECM mounts are accessible. By this time it was after 2pm on Friday afternoon, and they decided that they probably could not get the ECM completely swapped before the day was out. That would have stranded Odyssey inside the gates for the weekend, so we decided to get a fresh start on the problem first thing Monday.

The consensus was that the throttle drop-out was not actually harming anything, and so we decided to drive the 80 miles down here to Sierra Vista for a visit. We'll stay here at the Elks again tonight, and tomorrow afternoon we will head back to Tucson and spend the night outside the shop so that we can get a 7am start the next day on the ECM.

So the current status is that we're pretty sure the transmission is fine, and that we have not damaged anything further in the last thousand miles or so since the troubles began. Yet everyone is stumped as to the source of the problem. We're taking the very expensive step of replacing the ECM as the next step in the diagnostic process, but no one has any evidence that this will correct the problem. Moreover, what step will follow that is a big question mark -- I've already tested the wiring from the ECM to the throttle and it all checks out, and the ECM is not detecting any problem on its own. We have our fingers crossed that there is a glitch in the ECM itself, but that's hard to fathom with no other symptoms. The other thing that concerns me is that the problem only occurs under acceleration, and seems most prominent around the shift points, which may indicate some sort of synchronization problem between the engine and transmission ECM's.

In other news, Louise's dad will be celebrating his 70th this March, and they have invited us to join them on a cruise from South America to San Francisco. So even though we just returned from a cruise in Hawaii, and, left to our own devices we would probably not do another cruise in 2007, it looks like we will be spending the better part of a month cruising in March. I'll post the details here as I have them.

1 comment:

  1. Sorry to hear about your mechanical troubles. But I am impressed with your electrical knowledge. I too am having a electical problem with some exterior fog lights and unfortunately because of my limited knowledge, have to take it into the dealers. Any suggestions on or what I can study to improve my electrical awareness?

    Also in one of your pics, it looks like you have a deck on top of Odessey. That is WAY COOL.

    All the best,


Share your comments on this post! We currently allow anyone to comment without registering. If you choose to use the "anonymous" option, please add your name or nickname to the bottom of your comment, within the main comment box. Getting feedback signed simply "anonymous" is kind of like having strangers shout things at us on the street: a bit disconcerting. Thanks!