Hi skibum
To carry out any accurate diagnosis you will need a suitable diagnosis tester to check whats happening in the gearbox.If the oil level is ok and the car drives in reverse ok this could be a electrical issue or a transmission fault.
With a tester connected you need to look at the following items -
1.When the car is in drive does it display D in the kombi and also access the kombi functions via the tester and check if kombi is showing drive engaged.
2.check if all gear positions are shown correctly in kombi P,R,D,N ,1,2,3, and then with the tester the same again in the ecus for the gearbox,This ensures the transmission is being told what gear to select if this is all ok i would check again with the tester if a output speed is shown when in drive if not gearbox is not being driven.
If at any time in the testing you find the correct gear is not shown in the kombi this could be down to a faulty gear position switch which is mounted on the gear lever mechanism.
Regards Steve.
Unfortunately I do not have access to a diagnostic tester and "kombi" is Greek to me. When I place the selector in the various gears, the correct designator is showing up in the instrument cluster. Is there any way to verify what the transmission is being "told" by monitoring the output of the control module or solenoid inputs using a conventional DVM?
Is there anything to be gained by dropping the pan and checking condition of ATF filter, etc.? I note that the pump discharge pressure spec for reverse is almost double that of D...is it possible that the pump suction is partially clogged ? Or does the immediate nature of the failure point to electrical or position switch related issues?
One detail I failed to convey was that my son replaced the damaged shifter knob with an aftermarket unit (lacking the interlock button). I did not consider this as relevant information because the car operated just fine for several days with the replacement knob.
Sorry kombi stands for instrument cluster(German translation).
All you can test with a DVM at the ecu is the resistance of the solenoid valves but this it self sometimes not 100% test.
I would expect the car not to drive at all if the filter was blocked and when these filters block the normally cause a loud sucking type noise.
As for the new knob i would agree this should not cause you a issue as long as all gear positions are shown correctly in the instrument cluster as the interlock rod in the knob does set the travel in the lever for each gear position.
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