Thanks for the quick answers, the VSS tip, and the link to the service manual! Using the manual, I wasable to quickly locate the MSS and check it out visually, finding no apparent connection problems. I have a trusted friend who is the parts dept manager at my local Honda dealership and was previously a respected technician at a different Honda dealership. When I phoned him to order the mainshaft speed sensor, he told me that MSS code 15 problems frequently signify serious internal tranny trouble and that I should have a good tech run a full diagnostic on the tranny before going to the expense of replacing the MSS. He says the main problem that sets the MSS off is when the tranny countershaft spins at a different speed than the mainshaft and that serious internal clutch wear is typically what causes that phenomenon. I had AAA tow the car to the Honda dealership today for said diagnostic and will let you know what they say. Does their countershaft/mainshaft comment ring true to you? This car doesn't owe me anything and I've been lusting after a 5-spd anyway so if they tell me it needs serious tranny work I'll probably just sell it as is.

 

The code description indicates a fault in the MSS circuit. I don't think code 15 would be set by mainshaft slippage. The fact that resetting the TCU causes a brief period of acceptable shifting suggests the trans may be OK otherwise. When I had a bad VSS on my 97 Acura TL, it would shift OK after a TCU reset, until the code for VSS fault was again set, then shifting would immediately become very hard for the 1-2 shift. I'm not an expert on transmissions, so it's certainly possible that I'm wrong. I hope the Honda techs get to the bottom of your problem.

good luck

 

Honda dealer kept it for three days and test-drove it multiple times (they say); it coded (15 again) but wouldn't misbehave for them so they've advised me to try replacing the MSS and they didn't charge me.
I've ordered the part and will let you know if the problem shows up again after I replace it. Thanks again for your help and the quick answers.

 

You changed the sensor mainshaft?
Solve your problem?

Sorry for the English, I'm Brazilian.

Grateful.