My wife has a 2001 Honday Odyssey LX with about 110K miles. Hopefully unrelated history, we got a new transmission at 75K due to the recall.
Over the last few months, she has experienced intermittent "Check" engine light and "TCS" light coming on (they come on at exactly the same time), but then going off on their own. TCS is the traction control system. This first happened while she was on a roadtrip, and by the time she got home (1,000 miles later), the lights had gone off. It has happened again a few times in the meantime, but before she gets it to the shop, the lights are off.
The owner's manual indicates that an improperly installed gas cap may cause the check engine light to come on, and that appeared to fix it maybe once. The manual also says the TCS light may indicate a significant problem with the brakes, but they've been "checked" by two different shops with no problem.
The dealer checked the codes, said we needed a new EGR valve. Sounded strange, so I got a second opinion at a local small shop recommended by coworkers. He saw the same codes, replaced the EGR valve and followed some "bulletin" that said the Odyssey has a known issue with carbon buildup in the lines and to clear them with a drill bit or something like that. He then cleared the codes on the computer, and the lights were off.
My wife then drove the car for 2 days, and then headed out on another road trip. Of course, the lights came back on. She called the shop, he said that since she had just filled the car up with gas, it might be the gas cap improperly installed or maybe the gas cap seals have gone bad.
So I called ahead and found her a gas cap at a Honda dealer. She stopped, got the new gas cap, and they offered to check the codes (kudos to Glenwood Springs, CO Honda dealer - very helpful to a woman on the road!) which again say the EGR valve.
Any idea what this really is? Why would EGR valve also set off the TCS light?