My TP sedan is now running beautifully. The only problem remaining is the transmission being reluctant to change up.

I did a transmission service yesterday. Drained the fluid, replaced the filter, cleaned the magnets and filled up to the correct level with Mitsubishi transmission fluid. This didn't solve anything but at least I'm now working with known conditions.

The up and down changes are smooth as silk but the change pattern is far too agressive. i.e. If I don't back off the throttle dramatically, all changes happen at 4500 to 5500 rpm depending whether it is in economy or power mode. This is fine for top performance but I just want to drive quietly.

I've been reading the manual for the 2nd gen transmission, which I think is virtually the same. In economy mode, at anything less than 80% throttle and in power mode at less than 50%, it should change from 1st to 2nd at approx 10kph. Mine does not change until about 35/40 kph even if I back right off.

The TPS is adjusted spot on and I'm sure the TCU is working, so I am beginning to suspect one of the following:

(1) vehicle speed sensor (in the speedo)
(2) ignition pulse signal
(3) pulse generator B (on transmission)
(4) pulse generator A (on transmission)
(5) lock up clutch control solenoid valve
(6) pressure control solenoid valve
(7) shift control solenoid valve

Some of these will be easy to check and some a pain in the A, so I was hoping to eliminate a few suspects.

The 2nd gens have a diagnostic connector for the transmission control unit. Does anyone know whether the TCU for the TP has diagnostics and, if so, where is the connector?

regards
Coldamus

Thanks, Magna_Buff,

I have the chart for the diagnostics, so will have a go at it tomorrow.
I think now it has to be one of the pulse generators or, as you said, a wiring fault. I checked for visible faults and could not see any but will have to trace the continuity right through to the TCU. If I can get this fixed, it will be like a new car. It has only done 65,000 km and never been off the bitumen.

P.S. I can swap bits with my TP wagon if necessary. It is EFI but most should be the same except TPS. I got to the TCU but couldn't figure out how to get it out. I could not feel any bolts or any way to take the top off it - see pic.

regards
Coldamus

there are 4 screws on each side of the unit
to the floor pan one has an earth wire
you may have to pull the 2 wire connectors out to undo that side floor screws

check the wiring connections to the throttle body

I have had the throttle butterfly stick so make sure that is free moving

after the led testing and diagnostics reset tcu

just checking was the oil level in the middle of high and low on the dipstick
after the oil change
car running gearbox in neutral on flat ground?


Yes, I was very particular about the oil level. Before the oil change, it was over-full. I put in exactly 4 litres, then checked it and kept adding a hundred ml at a time until it was just right.

Thanks for the chart. All the changes are happening as if it was at full throttle. The 1-2 shift is where the problem is most apparent but it also happens on 2-3 and 3-4. It is not a problem on 3-4 because in the city, I obviously have to back off completely way before then. The biggest problem is when moving off from traffic lights. Even on 20% throttle, it starts revving out. To get it to change, I have to back off so much that there's a danger of being hit from behind by other traffic.

I still have my thinking cap on
was starting look into the isc servo at the throttle body because of the high revs

thumb nail
this is where to stick the probes then count the pulses

This morning I checked the two pulse generators and four solenoids. They all check out OK - i.e. their resistance is within range and the solenoids click when 12v is applied.

I could not find any diagnostic connector for the TCU. I dropped down the glove box in my wagon too and could not find one there either.

It is beginning to look as if the TCU is the only possible culprit. Damn! I really don't want to swap the TCU over with my wagon because then I'm likely to have two cars with transmission problems. Also the TCU is so hard to get at that I'm not keen on doing it more than once. I might wait till tomorrow and ring Mitsibits to see how much they want for a used one.

Before I do anything more I will see if I can confirm 12v and earth to the TCU.

the diagnostic plug is hidden away you may need a mirror
I take the glovebox right out 3 screws at the bottom of the glovebox to undo

wonder if it is throttle pedal switch at fault if it works its adjustable -if not its stuffed

Stop the presses. I found the diagnostic connector. On both of mine, it is not on a free cable. It is fixed in position in the upper rim of the glovebox cavity. Also it is a plug rather than a socket. Although large and about the size shown in your illustration, it only has two pins.

I don't know whether this is good or bad news but the diagnosis shows normal operation and no error codes. (just continuous regular pulses). Just to be sure, I checked my station wagon as well. Same thing.

Beggar. I'm back to square 1. I will check the accelerator pedal switch although from my reading of the manual, that should only be used to put the trans in second gear when idling in drive. Still I am running out of ideas so I'm glad you mentioned it.

Otherwise it is starting to look as if it is a mechanical / hydraulic problem such as the end clutch. The guy who reconditioned the transmission on my wagon is an expert, so I may have to refer it to him.

Edit: I checked the accelerator pedal switch and it does have a fault. The bracket that the switch is mounted on has been broken off and welded back on. It is positioned about one cm out of place, so the switch is not depressed when the pedal is at rest (foot off throttle). In fact the switch is never depressed. I will have to fix it but am sure it has no bearing on the current problem.

I also checked the transmission oil temperature sensor and that is working properly. Next to check is the kickdown servo switch. However I am going to have to take a break - can't spend all the holidays on this.

Ahah! I might have found the problem. I took one last look at it and checked the kickdown servo switch. It is supposed to be closed circuit with ignition off and open circuit with the engine idling in drive (handbrake on). It is difficult to ensure the meter is getting a good earth but mine shows several hundred ohms in both cases. i.e. it does not switch. I checked the station wagon and that definitely switches. So I guess I'm off to Mitsibits tomorrow. (a wrecking co. in Greenacre that sells both new and used Mitsubishi parts).

Thanks for all the help. After I've replaced it, I will let you know if the problem is solved.

My TP sedan is now running beautifully. The only problem remaining is the transmission being reluctant to change up.

I did a transmission service yesterday. Drained the fluid, replaced the filter, cleaned the magnets and filled up to the correct level with Mitsubishi transmission fluid. This didn't solve anything but at least I'm now working with known conditions.

The up and down changes are smooth as silk but the change pattern is far too agressive. i.e. If I don't back off the throttle dramatically, all changes happen at 4500 to 5500 rpm depending whether it is in economy or power mode. This is fine for top performance but I just want to drive quietly.

I've been reading the manual for the 2nd gen transmission, which I think is virtually the same. In economy mode, at anything less than 80% throttle and in power mode at less than 50%, it should change from 1st to 2nd at approx 10kph. Mine does not change until about 35/40 kph even if I back right off.

The TPS is adjusted spot on and I'm sure the TCU is working, so I am beginning to suspect one of the following:

(1) vehicle speed sensor (in the speedo)
(2) ignition pulse signal
(3) pulse generator B (on transmission)
(4) pulse generator A (on transmission)
(5) lock up clutch control solenoid valve
(6) pressure control solenoid valve
(7) shift control solenoid valve

Some of these will be easy to check and some a pain in the A, so I was hoping to eliminate a few suspects.

The 2nd gens have a diagnostic connector for the transmission control unit. Does anyone know whether the TCU for the TP has diagnostics and, if so, where is the connector?

regards
Coldamus

as i dont have much time to read the rest of the thread... the places i'd be looking is kickdown servo switch, fluid level or TPS as theya re the easiest to check and cos there is no other problems other than the transmission being reluctant to shift correctly.

wouldn't be any of the shift solenoids as the transmission still selects gears. Lockup clutch solenoid doesn't have anything to do with your problem. if it was the Pressure Control solenoid, you'd be faced with many other problems... trust me :P

the TCU has a diagnostics. yours being a TP, it remembers error codes where as TM/TN does not. take out the eci multi fuse (should be there even if your car is not efi) and that should clear errors.

get me on msn if ya wanna have a chat... i can send you a full service manual for the automatics.

Magna_Buff,

I haven't figured out yet how to fix the accelerator pedal switch. It might be easiest to break the weld and get the bracket welded back again in the right place.

Yes, the gear changes are quite smooth, particularly kickdown downshifts. I'm still not wholly confident that the kickdown servo switch is the cause of the problem. If I understand correctly, the switch does not initiate any gear changes or kickdown. It just informs the TCU of the state of the kickdown servo. I tried leaving its connector off (trying to simulate switch open) but I could not tell any difference when I drove it around the block. Tomorrow I will either buy one or swap the one from my wagon.

BCX7,
Thanks for the advice. I'll see how we go tomorrow. I printed out the service manual for the TR auto which seems identical (175 pages) so should have enough info. to go by.

Mitsibits were closed, so I swapped the kickdown servo switch from my wagon to the sedan. Ran around town trying to buy a pair of right angle, internal circlip pliers. Eventually got a pair at Total Tools. Had some trouble getting the circlips back in again after swapping the switches. It would be nice to have three hands.

Connected the wires up and took it for a drive. It seemed better on the 2-3 and 3-4 shifts but still reluctant to change 1-2.

Then I attacked the throttle pedal switch. It is impossible to work on it in the car so I disconnected the throttle cable, cut the wires to the switch and took out the whole assembly. As you can see in the first pic, the adjustable stop misses the switch altogether. I thought this was because the bracket had been broken off and welded back on. In fact, that is the factory weld and the switch is supposed to have a spring steel lever that extends past the microswitch. The stop presses the lever which then presses the microswitch when the accelerator pedal is at rest. The lever had broken off and you can see the remnants of it in the pic. The switch itself was Ok so I made up a lever using a leaf from a feeler gauge and attached it with a small bolt, nut and solder. As you can see in the second pic, this solved the problem.

I reinstalled it in the car and joined up the wires again (properly with soldered joints and heatshrink sleeves). Then I took it for another drive. It seems to move off from rest more positively now but I still have to back off the throttle a lot to initiate the change from 1-2.

I suppose I am being very picky. It is really not bad now - just a little annoying to be revving unnecessarily in 1st gear when trying to drive smoothly and conservatively.

All the symptoms scream "TPS, TPS" but I've checked it again and again. The only thing left to check now is the vehicle speed sensor in the speedo. However the manual only refers to that as follows: A faulty speed sensor may fail to activate the "fail safe" system or may activate the system when no fault is present.

There is no mention of it being used to signal shift points but I might as well check it and be sure.

that is a terrific fix up job

ellimiation of all possible electrical faults leaves the internal mechanical ones

next if you want to adjust the kick down band itself
do you have that procedure in the manual


Thanks. Yes I have the procedure. I've read it and it looks easy enough. However I will leave that until I've driven it some more. Short drives around the block are not enough to get an overall view of how it performs. Also, no-one wants to buy my wagon, so I will have to start fixing that - just valve stem seals and some cosmetic bits and it will be ready for rego. It is too good to waste and I actually prefer it to drive.

Yes, it screams TPS! Have you checked the connecting pins on the ECU, where the TPS connects. The pins in the plug may be corroded, or on the socket on the loom.
If both seem OK, try jamming the multimeter pins into the GND and TPS return pins (IE plug the loom into the ecu, and connect test leads into back of loom plug), pop the meter on the dash and make sure the meter reflects the throttle position. Also testing just the TPS does not allow for problems in the loom, where the TPS is working, but not getting the REF 5V to power it.

the tps reading is 0.5 volts if you are getting 5 volts you are on the wrong wire

Sorry for lack of reply. I have been away.

It is a carby model so there's no ECU, only TCU. I don't know which pins on the TCU to check.

However this issue is almost solved. I think I posted in another thread that the answer was in replacing the secondary diaphragm on the carburettor. When the secondary throttle was not working, I was inadvertantly using lots of throttle movement to get just a moderate amount of power. The TCU, through the TPS, interpreted the wide throttle opening as a high power situation, so it wouldn't change up until a higher speed.

Now that the secondary throttle is working, I am getting heaps more power, so need far less throttle to take off normally. The transmission now changes almost perfectly and is certainly OK in all the higher gears. It is still a little slow to make the 1-2 change and I've been looking for a way of adjusting the TPS linkage so that I can get part throttle before the TPS starts turning. In fact it may just be that I need to increase the idle speed as it currently idles at about 450 rpm.

the tcu is about right at that the idle with the car in drive should be abour 500 rpm at the lights...this is set by the tcu if this anoys you put the car in neutral at the lights then engage drive

carby i used to idle at 1100 rpm in neutral

efi sat steady at 1000 rpm in neutral

if both cars setup and sensors all worked well