Automatic transmission.

[Doug.V]

I have a 1990 240SX. With an Automatic transmission. It shifts well from first to second, but after that nothing ! Will not shift to third? Had to drive home at 25mph ! Where should i start? Any help appreciated.

[excitebike]

I am having a similar problem and I was wondering, how does 'Drive' work for you? Or are you limited to using 1 and 2...

[wiwalsh]

I also have an auto transmission (wish I had a manual, but thats a different story). It could be that your overdrive switch is dammaged or you have a loose connection between there and the transmission. I would check this switch. Do you have an orange light to the right of the dash that says "O/D OFF"?

Scott

[excitebike]

You bring up a good question. I assumed it had nothing to do with overdrive, because you can't even activate the Drive position... er, it works like 2nd. But I've tripped the O/D button without seeing the light. Do you know if the shift mechanism is electronically controlled?

[wiwalsh]

The transmission is controled by a computer, and a bunch of sensors. The transmission is smart enough to diagnose most problems so try this. (I know its a long procedure but it should definately help.

Here are some things to check out. First there is a self diagnostic procedure. This works on my 89 auto transmission. It should work on others. I know its a little crazy, but this sequence of events gets the transmission to go into diagnostic mode and a series of flashes will come up on your O/D Off indicator. This is straight from my FSM.

1) Start the car and warm it up to normal engine operating temperature.

2) Turn the engine off, moving the key to the full off position without removing the key.

3) Set the overdrive switch in the "ON" position

4) Move the selector lever to the "P" range.

5) Turn the key to the on position (Do not start the car)

Does the OD Off indicator lamp come on for about 2 seconds?(if yes, go to step 6, if not go to Diagnostic B below)

6) Turn key to the off position

7) Move lever to the "D" range

8) Set overdrive switch in the "OFF" position.

9) Turn key to on position (Do not start the car)

10)Move selector lever to the "2" range

11) Set overdrive switch in the "ON" position

12) Move selector lever to the "1" range.

13) Set overdrive switch in the "OFF" position.

14) Depress accelerator pedal and fully release it (remember car is off already at this point)

15) Set overdrive switch to the "ON position

At this point there should be a series of flashes on your OD Off lamp. I wont put all of the errors on here, but what you will see is a long flash and then a series of shorter flashes. If all the shorter flashes are the same, your transmission is "okay". If one, or several of the flashes are longer than the rest, then count which one is the longest and post it back here. Actually, I will give you the list of errors. There is 1 lead flicker followed by 10 judgment flickers. This sequence will end when you turn the key to the off position.

These error codes are for an '89 I would assume they still apply All flickers the same - okay

1st judgement flicker is longer than others - Revolution Sensor Circuit

2nd judgement flicker is longer than others - Speed Sensor Circuit

3rd judgement flicker is longer than others - Throttle Sensor Circuit

4th judgement flicker is longer than others - Shift solenoid A Sensor Circuit

5th judgement flicker is longer than others - Shift solenoid B Sensor Circuit

6th judgement flicker is longer than others - Overrun clutch Sensor Circuit

7th judgement flicker is longer than others - Lock-up Solenoid Circuit

8th judgement flicker is longer than others - Fluid temperature Sensor Circuit and A/T control unit power supply

9th judgement flicker is longer than others - Engine revolution signal Circuit

10th judgement flicker is longer than others - Line pressure solenoid Circuit

All flashes the same length (including the start flicker) could indicate low battery, battery has been disconnected for a long time, battery is connected conversely

Diagnostic B, if OD light dowsnt come onCheck Inhibitor switch, overdrive switch, kickdown switch, or idle switch circuit is disconnected or A/T control unit is dammaged.ped ped

[atomicdog]

thanks for the detailed post. could you also point out where the transmission computer is located? thanks a lot

[wiwalsh]

I believe the A/T control unit is just above the ECU on the passenger side. I havent actually looked for it, but from the diagram I have, I think thats right. Just to be clear, passenger side below the glove box, behind the outside corner plastic molding.

hope this helps, and good lick getting to the unit if it is actually there.

[topless@vabeach]

wiwalsh where did you get the info on the transmission test? I was looking for that info not to long ago. Is there a website or do you have the maint manual?

DJ

[wiwalsh]

FSM. if you really want to know this information that is the only way to get it.

[atomicdog]

Ok I finally got a chance to run the diagnostic and the instructions you provided worked just fine. My overdrive light bulb had burned out and I just replaced it now (For those of you who run into this problem and don't feel like looking for a replacement bulb you can just put in a LED with a small resistor, 1k or so, attached to one of the LED legs instead of a bulb). Anyways now to my question. All the flickers were the same length. Your post indicated there could be a battery problem. My car starts and all the lights and radio work, but the car has no power (it doesn't move at all). Could a battery problem cause this kind of problem? If so would replacing the battery fix this, or is there another diagnostic I can run to further pinpoint this problem? thanks a lot

[wiwalsh]

Well, not quite. There are two different scenarios that may be interpreted as all the same length. If everything is okay, there will be a break, a long lead flicker and then the rest of them are the same length. These will be relatively short (1/2 second each?). If the battery is the error, then you will have continuous long flickers (roughly 1 second or more each). there will be no lead flicker. this is how the FSM discribes them (hope all the spaces work out)

everything okay (1 is on 0 is off)

Lead 1 2 3 4 5 6 7 8 9 10

oo11111oo11oo11oo11oo11oo11oo11oo11oo11oo11oo11

All the same length: Battery problem

oo11111oo11111oo11111oo11111oo11111oo11111oo11111