1UZ - A340f stopped shifting in drive

[clyde7]

Hi.
I have a 1UZ, A340f using the factory ECU. The transmission has suddenly stopped shifting when in drive.

I have checked (at the ECU) BATT, B+, NSW, STA, IGSW and they all seem to have power when necessary. I measured there signal between NCO- and NCO+ and also between SP2- and SP2+. The signal has an increasing frequency as the RPM and speed increase (wasn't sure what else to measure but presumed the ECU is triggering on the rising/falling edge). Putting meters on S1 and S2 while driving in D show 12V and 0V respectively and don't change at the point I'd definitely expect a gear change. These solenoids click if I manually apply 12V.

I also tried removing the main transmission plug; R, L and 2 are all fine and when in D it 4 as, I think, is expected.

I was hoping to get some advice or suggestions as to what the problem may be.

Thanks in advance

 

[P Bateman]

Just to be clear, when you accelerate in Drive, the transmission stays in first and wont shift into second?

Does the transmission behave normally when you shift manually into 2 or L positions?

If thats all good, based on your measurements of S1 and S2, if it wont shift into second then I would be checking the S2 wire for an open circuit or poor connection. Not sure if the kickdown switch could cause problems if its stuck on so it may be worth inspecting as well.

Toyota gearboxes of this age can also be test driven with solenoids disconnected:

• L Positon should be first gear
• 2 Position should be third gear
• D Position should be overdrive

This tests all the clutches & brakes in the gearbox manually (without electronics) and is an easy way to find out if your issue is electrical or hydraulic/mechanical.

Let us know how you go.

 

[clyde7]

Just to be clear, when you accelerate in Drive, the transmission stays in first and wont shift into second?

Does the transmission behave normally when you shift manually into 2 or L positions?

If thats all good, based on your measurements of S1 and S2, if it wont shift into second then I would be checking the S2 wire for an open circuit or poor connection. Not sure if the kickdown switch could cause problems if its stuck on so it may be worth inspecting as well.

Toyota gearboxes of this age can also be test driven with solenoids disconnected:

• L Positon should be first gear
• 2 Position should be third gear
• D Position should be overdrive

This tests all the clutches & brakes in the gearbox manually (without electronics) and is an easy way to find out if your issue is electrical or hydraulic/mechanical.

Let us know how you go.

Thank-you so much for the response.

Yes that is right, it stays in first and won't shift to second. Even when pushing the RPM beyond where I know it should have changed.

Yes, the transmission seems to behave fine when I manually select 2 or L.

S1 and S2 measure about 16ohm to ground at the ECU plug, so I think the wire is okay. When I apply 12V to S1 and S2, at the ECU plug, I hear the solenoid click. The voltage at S2 never seems to change to 12V. I had a one meter on S1 and another on S2 while I drove and the voltages don't change. I was not aware of a kick down switch (or even what it is - Google helped with that) - do you possibly know which pin it would be connected to?

It probably wasn't clear in my original post but I did remove the plug to disconnect the solenoids (and the sensors, etc) and then drove the car. In D it is overdrive and L seemed like first. I didn't notice 2 being third but it definitely engaged a different gear. It does seem the gearbox mechanically is okay.

 

[P Bateman]

Soarer Troubleshooting guide points (in order) to:

1. Shift solenoids
   While the shift solenoids seem to be within spec and click when energized, that doesn't mean much if the solenoid is blocked or damaged
   
   
2. Throttle Position Sensor
   Check voltage sweeps at VTA pin on ECU when you move the throttle
   
3. Vehicle Speed Sensor 1
4. Vehicle Speed Sensor 2
   If they're pulsing, then thats encouraging
   
   
5. Valve Body 1-2 Shift Valve
   Shift valves have known to jam or leak - plus the 1-2 value is normally the busiest valve in the gearbox
   
   
6. Park Neutral Switch
   Check voltage at each of the position inputs at the ECU
   
   
7. Gearset B2 Brake and F1 One-way Clutch
   The one-way clutch is a known weak point in the A340. Have you been giving it a hard time?
   
   
8. ECM

.

Kickdown pin on your ECU will depend on the model year and vehicle - but if it's there, the abbreviation in the diagrams is KD.

Do you have any trouble codes?

 

[clyde7]

Soarer Troubleshooting guide points (in order) to:

1. Shift solenoids
   While the shift solenoids seem to be within spec and click when energized, that doesn't mean much if the solenoid is blocked or damaged
   
   
2. Throttle Position Sensor
   Check voltage sweeps at VTA pin on ECU when you move the throttle
3. Vehicle Speed Sensor 1
4. Vehicle Speed Sensor 2
   If they're pulsing, then thats encouraging
   
   
5. Valve Body 1-2 Shift Valve
   Shift valves have known to jam or leak - plus the 1-2 value is normally the busiest valve in the gearbox
   
   
6. Park Neutral Switch
   Check voltage at each of the position inputs at the ECU
   
   
7. Gearset B2 Brake and F1 One-way Clutch
   The one-way clutch is a known weak point in the A340. Have you been giving it a hard time?
   
   
8. ECM

.

Kickdown pin on your ECU will depend on the model year and vehicle - but if it's there, the abbreviation in the diagrams is KD.

Do you have any trouble codes?

Thanks for all these items. I tested what I could so far but was a little unsure of how to test some of them.

1. Not sure how to test the solenoids. I was thinking of manually manually applying 12V to S2 while driving to see if I get a change from 1->2.

2. I tested the throttle position sensor and it I have between 0.3 and 3V as I press the throttle pedal

3. 4. Both speed sensors appear to be sending a signal. I see the frequency of the signal increasing and decreasing.

5. I am not sure how I would test this. I guess if I get a gear change in the test for 1. then it is okay?

6. I tested the voltages at NSW and STA and they appear correct (as per the schematic). When switching the key to start: NSW gets 12V in any gear while STA only gets 12V when in park. Are there any other inputs to check?

7. No, it is never driven hard.

8. Sadly, I have a feeling this is probably where the problem lies.

 

[P Bateman]

1. Yes, that's what I would try too.
2. Sounds OK
3&4. Sounds OK
5. The test from #1 would either isolate it as a fault, or confirm it as a possible cause.
6. NSW and STA are for starting only - you should also have position inputs from each shifter position back to the ECU (i.e. PRD2L)
7. Are you kidding? Why the hell not???
8. Its easier to replace than a valve body.