MA61 Auto troubles - No Overdrive

[demios]

I've been playing with Impurist's newest MA61 and it's got some issues with selecting overdrive. We've already replaced the fluid and changed the filter, which did make everything feel a lot smoother, but it still won't stay in 4th.

We finally went for a decent drive and got the car up to 100km/h, and when I turned overdrive on, it tried to get into gear, but slipped back to 3rd almost immediately and stayed that way while we were driving. Occasionally every 5 minutes or so it'd try to shift again, but end up staying in 3rd. Also, it didn't try to shift into 4th every time I toggled the Overdrive switch.

I'm thinking that it might be a solenoid, but my understanding is once they die, they're dead and don't occasionally toggle like this. My other thought would be associated wiring or the computer, but I'd assume I'd get an engine fault light if that were the case?

Anyway, does anyone have any suggestions or advice on how to diagnose it before I just replace the solenoid and see what happens?

[thechuckster]

auto won't stay (or engage?) in O/D if the engine temp isn't up to normal. The MA61 trans ECU piggybacks off the Engine ECU sensor. it'll also disable O/D if it thinks road speed is under a limit (60km/h i think) or engine speed is low (idle?)

If the solenoid was faulty, it would never engage 4th.

TSRM: MK2 TSRM On-Line
it may help but it is for a chassis that came with a 5MGE motor.

The TSRM suggests 4 signals from the ECU, the coding on this page suggests at least idle (IDL), rpm, and two others (temp? and ??). <deleted, see below>

The TSRM has a fault diagnosis section that you can follow.

It uses the OD light for displaying error codes, requires the DG pin to be grounded.

edit: OD1 has the temp signal from the ECU, L1-L3 seem to be TPS related, maybe it doesn't get an RMP signal and relies on SP2 to indicate engine/input speed. Anyway, heaps of diagnosis things in that TSRM to keep you busy.

[wilbo666]

Charles, I think the 5mge stuff is a bit different to 5me

I had a feeling that 5me had a temp sensor in auto for the auto...?

Cheers
Wilbo

[thechuckster]

fair enough, i was thinking it might have been a bit more advanced seeing as it got the star wars dash and overly-complicated climate control

If the 5ME is like the RA65 auto, the coil-side of the o/drive relay earths thru a temp switch that goes closed-circuit when the engine coolant is warm (any idea where that temp sensor is physically located?). If that's the case, it shouldn't be able to energise the solenoid with a cold motor. If it has a similar cruise setup to the rA65, the cruise ECU can also de/energise the solenoid.

If it's briefly engaging - is the light going on/off or is it just the gearbox that's dropping in/out of overdrive.

[demios]

I haven't noticed any lights for Overdrive on the car, it's just a toggle switch next to the shifter. I've tried looking for one, but haven't been able to see one.

When I've tried to test it, the car's been at running temp, and I've been doing 90+km/h. After the oil and filter change, I'll turn overdrive on, it'll try to upshift to 4th, go back to 3rd and stay there for 5 minutes or more.

Before the oil and filter was changed, it'd try to shift into 4th, but keep on dropping back to 3rd. Was really frustrating when driving around 70km/h in traffic.

I haven't had a chance to diagnose the issue further, and probably won't until the weekend, but I had a bit of a read through the TSRM you linked. Looks like it will be quite helpful. Thanks!

[thechuckster]

on the RA65, the over-drive switch is next to the shifter and the switch itself lights up when pressed.

A quick fix/test might be to bypass the switch/relay/sensor and just wire up 12V from an IGN source, feed it thru a switch and connect it to the solenoid. If the gearbox still drops in/out then it's inside the box, if it stays engaged - point finger at electronics.