Hey all - just installed a new cylinder head and timing chains on Mums TS 2.6, and now the auto is playing up... :(

Didn't touch the transmission obviously while doing the cylinder head, but did undo the transmission mount ( to allow enough engine movement to get the bloody crank pulley off!) so figured I had bumped a trans sensor connector block maybe.

Symptoms - engages reverse and drive fine, and will take off the first time in first gear ok.

But wont shift up until close to 5000rpm, and then shifts into third gear (limp mode) with a thump and stays in third even if I come to a stop. Switching off ignition and restarting will bring back first gear until that high rev thump and third again.

My reading of the workshop manual tells me the only way to clear the fault codes is with the diagnostic computer - true? How else could I clear the transmission ECU codes and start again (having cleaned and checked all the connectors I might have disturbed)?

The transmission was behaving fine until I spent two days mucking about on the engine!

A big thank you for the genius engineer that decided to bury the transmission ECU under the heater assembly :( What a fundamentally stupid design. I usually say positive things about the Magnas, but this drives me nuts...

I would be checking all the wiring around the trans, and any you have removed when doing the head, you may well have moved something, like sensor wiring on the box, TPS etc. AFAIK the second gen trans puter doesn't store fault codes (I could be wrong) but goes into limp mode when it finds a sensor signal is missing. Definitely sounds electrical to me. A mechanical fault in the box would put it in limp mode straight away, rather than what yours is doing. My bet is the TPS connector.

FYI if takeoff is in 1st its not in limp mode. limp mode will take off in 3rd and stay in 3rd until it is sorted (atleast this happened on Peter_Pan's KR verada when it was limping)

Same thing you are explaining, takeoff in 1st, redline, clunk into 3rd happened to Peter_Pan's car when he blew his gearbox trying to keep up with me!

Nope, it starts off ok then goes into limp mode. TCU detects a problem, goes into limp mode but switching it off allows him to start in first. So its electrical, not mechanical. Don't assume the gearbox is "blown" until you have done more basic checks. Probably one of the shift solenoids, or wiring to one, was damaged in the head work.

Checked all the connections and wiring, and all looked ok... Ran out of time so will be looking again on Monday (didn't even get time to sit down with a multimeter and interrogate the ECU). Picked up a spare ECU from pickapart anyway just to have it on hand (the car lives way out in the country).

I always assumed electrical, so fingers crossed its a dodgy connection. The engine bay is pretty grubby as it had some serious oil leaks before and lives 10km up a dirt road! One task is serious cleanup - wish I could have done it before doing the head (but the car was dead and wasnt going anywhere near the pressure wash...) as I hate working on grubby engines. You get grubby and spend too much time cleaning around things...

But as pointed out, its starting in first so the ECU is probably fine - its doing exactly what its supposed to when it senses a fault. And the fact its revving out in first before going into limp does point to the TPS (or maybe the transmission's road speed sensor).

Feeling fairly foolish now. Just a wire for Pulse Generator A yanked out of the plug next to the transmission mount. Looked perfectly fine externally, but the mulitmeter showed the fault - a light tug on the wire and it fell out... Thought they had plenty of slack in them to allow a bit of engine movement with the mounts off, but I guess not!!

Bypassed the plug and voila :)

Anyone want a TCU...? :)

Haha! Told you so! Anyway, good that it was a quick fix. Often, finding the problem is the hard part.

Those wires and connectors cop a lot of heat in normal use and are bound to get a bit iffy after a few years.

On the 2.6 manual its the reverse light switch that does that when you drop that side of the engine.

Never doubted you mate ;) As soon as you said the TCU is fine because it starts in first, the light immediately dawned!!

Took me a little time today, as it behaved itself once just to confuse me!!! That yanked connection must have transmitted current just long enough for a couple of gears changes and then quit again, leaving me scratching my head. But the TCU was diligently giving me fault codes that pointed at the Pulse Generators, so was just a matter of going over everything with a multimeter ;) The system works :)

Although its a bit tricky getting fault codes with a digital multimeter - an analogue one would show the long and short pulses much clearer!!

All good. I applaud your fault finding skillz! lol

All good. I applaud your fault finding skillz! lol

Mate - I have owned, restored and driven daily about 15 old French cars over the last 15 years. Fault finding skills is one thing you develop really well :)

Its taken me a little while to get my head around the illogical and weird way the Japanese screw their cars together, but once adjusted its a breeze!

Tres bien mon ami.

Hi Renoman,
My TR is now doing the exact same faults as your was.

Can you tell me more about the connection that "loose" and intermittent.
My TR starts ok in first but as soon as i get it into 2nd it Revs out to third and gets stuck in limp mode.
I have checked TPS, Air Intake sensor, hoses, dizzy cap and given it a trans flush.
I am near certain this is electrical fault of a sensor fault to the TCU.

If you can let me know where the wire for "pulse generator A" is found then i can see if this is the cause or not.

Thanks

Disregard please.

I jumped the gun a bit. All i needed to do was give the TPS connector a really good clean.
Was filled with gunk and stuff and this caused my TPS to play up and cause limp mode to occur.
So glad that is all it was because finding a new TPS was getting difficult as not all wreckers having one to suit my magna.

Sometimes it the easiest basic fault that is the cause and usually for me these easy basic faults are the ones i overlook first!

Thanks