Hi Guys,
I have very recently purchased a used Toyota MR2 Spyder 2000 Sequential Manual from the RAC driving centre (unregistered) at 30 000 kms. I have since passed registration however, the vehicle has an intermittent issue with the transmission (which is the stock 5-Speed Sequential). I have taken her to a Toyota dealer who performed a diagnostic and found the following error codes:
P1646 - Transmission ECU Malfunction
P1647 - Car Communication Malfunction
P1882 - M/T Code Shift Sensor Malfunction

When cruising normally in 4th gear at approx 60kmph (no high rev transitions or labouring engine) the smt warning light appears and the car will not allow any gearshifts up or down using neither the steering wheel shifter buttons nor the shift lever. There are no clunks or abnormal noises. The car is still able to drive in 4th however, the car stalls once the car comes to a standstill (then the check engine light comes on). The car will not register as being back to neutral until the key is placed in the off position and then put back on. The engine then starts as normal with no error lights showing.

To fix this we got the Toyota dealer to carry out a transmission fluid flush (with the correct synthetic oil as this was a suggested fix on some forums) and a 30000 km service was completed - no other issues were found.
 
The problem still persists.
 
I was looking to see if you guys had any experience with this issue or other similar issues and what you would suggest to remedy or diagnose the issue as it is a wonderful car to drive!

Many thanks in advance for any help you may be able to provide!

Callum

I had similar issues and it most likely will be the sensor, seems when sensors have issues it throws Ecu & tcu codes. I'll look in the bgb on your codes for troubleshooting and if it's easy to change the sensor!

Thanks that would be amazing! We'll be heading down to Toyota to order the replacement sensor over the next few days, if you could identify the specific name/any further detail as to how difficult it would be to fit that'll be excellent

So had a look and p1882 comes up as shift stroke sensor, which is at the back of the gsa which is behind the hpu.
First picture is of the gsa, then of the gsa sensors and last one on how to change it.



Hope this helps, all 3 stroke sensors are the same, and you'll need sequential m/t grease not the same as fluid!
You can look up part number at toyodiy.com

Thankyou so much! I've been in contact with Toyota who appear to have no idea further driving suggests that the problem occurs in gears other than fourth but always when sitting on a specific rpm for an extended duration: 5 seconds or greater (approx 2200 rpm)
Does this still support a faulty gear shift sensor or could it be something else also?

i couldn't say, i googled your code and not enough consistent issues to confirm. some say it skips 4th gear straight to 5th or don't get any forward gears only reverse or it stalls.
To confirm if it is the sensor they've swapped it with clutch sensor to see if it throws the code.
 
Toyota dont seem to have many experts on the smt but rather follow what the computer tells them. 
Terry at road and track in qld has plenty of experiance with the smt, an ex spyder owner in sydney went to castle hill toyota a few years back and they seemed to know there stuff and heard parramatta toyota does too.
 
 

Hi My 2002 MR2 spyder has been having intermittent problem of engaging reverse gear. Now completely cannot engage reverse, and it bleeps and can hear thumping sound as if its trying to engage. Others gears are ok and there is no smt fluid leak. Hv checked fluid levels and they are ok.

hmmm i have read a few people over in the states having similar issues and it was the tcu (transmission control unit)
First thing check is a light showing on dash board like this ( ! ) this would mean a code is being thrown and get that checked.
Next if no code
Try a full relearn which would mean either get a obd2 reader with techstream and it will completely relearn all the gears and wipe all the data to start fresh! Or you can go to Toyota to do this too!

Before you start changing anything!

You can read more on what others do jump on spyderchat.com more of us on there

Aussiespyder is completely correct. Forst step that needs to be done by a toyota dealer is a full relearn. As clutches wear time goes on, a relearn needs to be done. This is one of the most common issues, and if not sorted out in a reasonable time can also cause compunding issues.

The most common reason a transmission ecu ever failed in one of these cars was a roof leak. The car you bought doesnt have any roof issues does it? As the ecu and tcu are bot located under the passengers side storage bin, which is a location prone to moisture collection, which as you can imagine causes issues with electronic components.