Yaris Mmt - No Drive

[sceh]

Possibly not a new topic but a variant.

My Yaris will, fairly frequently, have no drive but there is no gearbox warning light as there used to be. If I switch off and then on again after a few minutes it will usually go again after 3-4 tries.

Curiously I just tried using an OBD2 scanner and this started just after reading codes. However, no codes from the ELM scanner related to anything other than not being able to read an oxygen sensor. The engine runs fine.

Why no gearbox light?

thanks

[MikeSh]

Can you be a bit more specific about the symptoms? "... have no drive" is rather vague.

What circumstances does it happen? Cold, hot, in traffic, while in D, when moved from N to D, ... ?

[sceh]

No drive means the engine runs OK but in D or R or manual select there is no traction so the car does not move at all. It happens when it is cold mainly because it rarely has time to get warm but I tired running the engine for while yesterday and it seemed better. I don't really have decent statistics yet. However, there is no engine warning light or gearbox light and no flashing N

[MikeSh]

OK, still a bit vague though.

Does it not give traction only when you go from N to D or R, or does it sometimes 'drop out' at some point when driving (eg. when you stop at lights) and then fail to work for a while?

If the former, can you hear it engaging when you select D or R? They often make a bit of a clunk, especially if you increase the idle revs a little bit. If it isn't engaging I'd expect the detectors to notice and give a fault. But it depends where they are in the linkages - if they only detect the actuator travel they might not 'see' a bad link between the actuator and gearbox.

On the other hand it might be the clutch not engaging properly.

[sceh]

it drops out when driving and when I stop and restart the engine, I hear the clink when I go into D or R but there is no drive. Increasing the revs makes no difference

[sceh]

If it were the clutch not engaging would there not be an error code and warning?

[MikeSh]

it drops out when driving and when I stop and restart the engine, I hear the clink when I go into D or R but there is no drive. Increasing the revs makes no difference

Dropping out while driving sounds rather like a linkage or gearbox problem (same as you can get with a manual (this is a manual gearbox at heart)). So probably beyond the reach of the MMT detectors which is why no indication.

Actually, that's a point - does the dashboard indicator go to or stay in D or R when this happens? If it goes to N it might be the selector itself that is playing up - bad contact or something.

If it were the clutch not engaging would there not be an error code and warning?

Again, if there is a hang in the mechanism it may not be detected - the clutch bearing/plate travel is very small, so it's hard to actually detect 'engagement'.