2001 Leganza Auto. U3F00 fault code ???

[lobe]

Hi,

Sorry for the waffle (below) but the history might help someone smarter than me help with this problem. Suspected serial data link, comm link problem? Only fault code when read with snap on OBD is U3F00 ?, it just re appears when cleared ?

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Daewoo Leganza Oct 2001 2. 2L Auto. Australian model. Transmission won't shift from 1st when shifter is placed in 'D' ( can be operated like a semi auto so is drivable - see last couple of paragraphs )

The trans ( Aisin Warner 50-40 model ) will not shift out of 1st into 2nd, 3rd, 4th in D. This problem occurred after girlfriends 15min drive on the motorway/freeway, after exiting on the down ramp & coming to an intersection, then wouldn’t change out of 1st. I picked the car up 3hrs later, disconnected battery for 5mins, checked trans oil level after warm up, then drove car. Wouldn’t shift from 1st.
Thrashed it abit in 1st round near top of rev range and it shifted gears. Auto trans working again. After 15 min drive back down freeway, same problem.

Check Engine Light (CEL) had been on for ages prior to fault ( suspected cam sensor ) so difficult to say when a suspected transmission fault problem occurred, other than physical problem of it failing to shift from 1st.
The ATF oil was not burnt but i flushed it anyway, inc disconnecting cooler line to empty torque converter of old oil etc.
Replaced with new ATF. Still the same problems - stuck in 1st gear, accelerating high into rev range in car caused it to shift again, but after brief drive at highway speed, transmission would stick in 1st after slowing down at intersection etc, when the trans shifted down upon slow down but would then not shift up as speed increased.
Accelerating quite high into rev range causing car to then shift gears only worked for say 3 – 4 times. Now non shift from 1st problem cannot be cleared by just accelerating high in rev range.

Scan some showed fault codes - for cam sensor, crank sensor & park neutral switch (in memory from older problem, since replaced).
1. Cam, crank sensors replaced. Park neutral switch disassembled and checked - ok.
2. Batt disconnected for a few hours to clear ECU. CEL still on. Problem still persisted

3. Disconnect batt. Clear ECU. Fit 2nd hand TCM (transmission computer) , SOME SUCCESS – no CEL on. Suspect this has been cause of CEL been on for ages. Transmission still won’t shift in D. Tried a 3rd TCM just to be sure, same result - no success.
4. Tried 2nd hand ECU with no success - transmission still won’t shift in D.
5. Park neutral switch disassembled and checked - ok.
6. Check gear shift cable and adjustment, park neutral switch setting – all ok.
7. Vehicle speed sensor appears Ok, as speedo is working ok.

Note : The vehicle speed sensor did fail about 3 months prior to trans shift problem, resulting in speedo not working. Transmission still worked as normal. Sensor had failed mechanically. Replaced with brand new OEM part. Speedo worked again.


The car can be still driven, by using the following method, to allow it to shift like a semi auto, as per owners manual.
1a) pressing the hold button down on the gearbox, put gear/shift lever into the # L position - gearbox holds 1st only.
2b) Move gear/shift lever into #3 position - gearbox then shifts and holds 2nd gear only.
3c) Move gear/shift into D - gearbox then shifts and holds 3rd gear only.

This method is ok but obviously doesn’t shift into 4th when in D and hence not suitable for motorway, highway driving etc. Transmission is actually capable of getting 4th gear - by disconnecting trans computer completely - i. e then it has obviously gone into limp mode (L holds 1st, 3 & D hold 4th as per owners & workshop manual)

Only fault code when read with snap on reader is U3F00 Huh?, it just re appears when cleared Huh?

Trans valve cover removed & shift solenoids checked. All operate ok. All ok with resistance check. Wiring harness inside trans checked for continuity - all ok.
Continuity from TCM pin 11, to OBD/DLC pin 2 all appear ok. Ok from tcm pin 11 to ECU pin B13 ( serial data link between tcm/ecu ).


Any ideas, help would be appreciated
Thanks.