***FIXED*** 1995 240SX (S14) Auto Trans Shifting Problems

[gtd65]

I posted most of this in formation in another thread but I think it's time for an S14 thread rather than the S13 Convertible
Here: 94-240-conv-with-at-shift-problems-t96505-200.html

by gtd65 » 02 Nov 2010 10:01
Our trusty (maybe not so much recently!) '95 240SX has been laid up for the past 6 months or so due to the brake pedal switch stopper disintegrating. Well I'm back over in Florida for the rest of the year and we finally got around to fixing that issue last night - what a PITA that job is

Well after fixing the brake light the CEL light came on (I've not had this checked yet) and I noticed that the car is very slow to upshift (it's an auto) to 2nd gear from 1st.

I'm hoping this is just because it's been sitting for a while and needs a bit of a run to sort things out, however, having read most of the information here - does this also apply to the S14?

by gtd65 » 02 Nov 2010 15:34
Well I took a trip up to Advance for a CEL diagnostic check, the error codes were as follows:

1. PO325 Knock Sensor / CKT Malfunction BNK / or Single Sensor.
2. PO/31 Gear 1 Ratio Incorrect
3. PO/32 Gear 2 Ratio Incorrect
4. PO/33 Gear 3 Ratio Incorrect

On the way up to the store the transmission was changing up more slowly than usual but it appeared things were getting better the closer I got to Advance

The guys at Advance had a look at the codes and reckoned the problem is more than likely due to the car sitting for a while and recommended using "Seafoam" and driving around for a while to see if the problem continues.

The CEL was cleared and so far it's not reappeared.

I've never actually done a fluid change on an auto box to date - there seems to be two schools of thought:

A..Change it per the manufacturers recommendations.
B..Never touch it at all

I've always gone with option B and other than this issue not had a problem.

Is it easy enough to do an auto-trans fluid change or flush with minimal tools/equipment?

by gtd65 » 01 Mar 2011 22:46
Well our S14 still suffers from this problem - I can work around it to an extent by changing the throttle position to "manipulate" the gear change but my GF just simply does not seem to understand the concept of doing this...

Can anybody point me in the direction of the location of the rev sensor on the S14?

by gtd65 » 05 Mar 2011 10:52
Can anybody clarify which sensor I should disconnect on my S14 then?

Please see pics below and numbering sequences provided for guidance.







I've only really got this weekend to try to sort this out, as I'm off to WA state at the end of next week... gonna be a bit cooler to say the least!!!


by gtd65 » 05 Mar 2011 12:29 OK then here is a summary of what I tried today:

FAIL

A. Drove the car as normal - when engaging DRIVE the car lurches into gear and will stay in 1st gear until approx 4000RPM and then shift into second gear - car needs to be driven over (at least) 40MPH before it will up-shift into any higher gears.
B. Disconnected sensors 1 through 3 (individually) and car drove with the same characteristics as item A above - so no effect noticed.
C. Disconnected sensor 4 and when putting car into DRIVE no hard shift observed (definite difference). Car drove as if in some sort of "economy mode" with little or no feeling of power at all - suspect this is a mode where a single higher gear is selected? Car did not up-shift at higher speeds and appeared to be driving in a mono-gear...

Edit: Forgot to mention that with sensor 4 disconnected I can select 1st gear and drive off and then push the selector to 2nd and it will up-shift but continuing to DRIVE does not engage a higher gear - perhaps the car is stuck in 2nd gear when disconnecting sensor 4 after all?

So...

Disconnecting sensor number 4 seems to be the one that applies for the S14 but doesn't help my problem out so far.

One thing that I noticed, despite driving only relatively short distances, the car appeared to be pretty hot under the hood, even although the temperature gauge was in the normal position?

Any ideas based on any/all of the above?

Cheers in advance

[gtd65]

nada?

[gtd65]

Well i'm currently up in Washington state and still looking for a possible solution to this problem...

[Mercury_Hg]

C. Disconnected sensor 4 and when putting car into DRIVE no hard shift observed (definite difference). Car drove as if in some sort of "economy mode" with little or no feeling of power at all - suspect this is a mode where a single higher gear is selected? Car did not up-shift at higher speeds and appeared to be driving in a mono-gear...

Edit: Forgot to mention that with sensor 4 disconnected I can select 1st gear and drive off and then push the selector to 2nd and it will up-shift but continuing to DRIVE does not engage a higher gear - perhaps the car is stuck in 2nd gear when disconnecting sensor 4 after all?

This happens to me intermittently. The car starts up in second and will only go into first if I put the selector in first. Otherwise it stays in second and will not shift to third. What does this mean for me? I have an S13.

To fix it, I have to stop, put the car into first, turn the car off, put the car in park, and turn the car back on.

[gtd65]

C. Disconnected sensor 4 and when putting car into DRIVE no hard shift observed (definite difference). Car drove as if in some sort of "economy mode" with little or no feeling of power at all - suspect this is a mode where a single higher gear is selected? Car did not up-shift at higher speeds and appeared to be driving in a mono-gear...

Edit: Forgot to mention that with sensor 4 disconnected I can select 1st gear and drive off and then push the selector to 2nd and it will up-shift but continuing to DRIVE does not engage a higher gear - perhaps the car is stuck in 2nd gear when disconnecting sensor 4 after all?

This happens to me intermittently. The car starts up in second and will only go into first if I put the selector in first. Otherwise it stays in second and will not shift to third. What does this mean for me? I have an S13.

To fix it, I have to stop, put the car into first, turn the car off, put the car in park, and turn the car back on.

I guess you should firstly try the link in my first post of this thread and see if you can figure out which one is the sensor for the S13?

Maybe you just need to unplug the sensor/connector and it might cure it....that's what the S13 guys found worked for them...

[gtd65]

Well, I'm back down from Washington state to Florida and looking into the transmission issues once more.

Took the car out for a good long ride with sensor #4 disconnected.

This is find for simply running around town at low speeds but isn't really an option if out on the highway.

So anyway, after driving around in town and out on the highway I noticed the check engine light had come on again.

Decided to check the codes at Advance Auto Parts - managed to find a total of 12 codes.

I'm sure the majority are due to having the sensor #4 unplugged of course

So from the top here they are:

P0705 Transaxle Range Sensor Circuit Malfunction (PRNDL Input)

P0720 Output Speed Sensor Circuit

P0731 Gear ratio error in 1st gear.

P0732 Gear ratio error in 2nd gear.

P0733 Gear ratio error in 3rd gear.

P0734 Gear ratio error in 4th gear.

P0750 Shift Solenoid A Malfunction

P0755 Shift Solenoid B Malfunction

P0740 Torque Converter Clutch Circuit Malfunction

P0745 Pressure Control Solenoid Malfunction

P0710 Transmission Fluid Temperature Sensor Circuit Malfunction

P1760 Overrun Clutch solenoid valve

(The P1760 code is detected when the Transmission Control Module (TCM) detects an improper voltage drop when it tries to operate the solenoid valve.)

Codes were cleared (sensor #4 was reconnected before the test) and the car performs as normal witht he hard shift from 1st to 2nd gear at 4000RPM.

Any clues?

I think it's a sensor/electrical issue

[gtd65]

I forgot to mention that I can also put the car into 2 and use first and second gear without having to go to 4000RPM.

I have to use 4000RPM to get from 1st to 2nd gear if D is selected....

[gtd65]

Well I've been doing quite a bit of reading since last night and another culprit might be the TPS - even although there isn't a code for that showing.

I did change the TPS a few years back and according to my reading efforts the TPS is known to be generally unreliable - this is news to me on a Japanese vehicle but then again I am experiencing problems.

Looks like a trip to the store for a multimeter in in order today....

Any other tips or suggestions please don't hesitate to holler!

[gtd65]

Well, despite not having a TPS error code (or obvious TPS problems) - the TPS was showing readings well out of tolerance for the car.

Just changed the TPS today - which is the second TPS the car has had since owning the vehicle - and now the gears are changing perfectly!

It's taken a while to get to the bottom of this but it was a very cheap and easy fix now that it's over!