Tranny control unit fail-safe mode??

04-29-2004, 01:42 PM
Has anyone heard of this particular problem? I copied this description of the problem from an article on the net somewhere.

Poor acceleration, stays in 3rd gear. If the cranking voltage on some 2000 G20 models goes below 8 volts, the automatic transmission control unit may enter fail-safe mode. If this happens, the owner may complain of a lack of engine power, with the transmission remaining in 3rd gear at all times. Also, the MIL will not illuminate and DTCs will set indicating failures in the Vehicle Speed Sensor-Automatic Transmission/Vehicle Speed Sensor-Meter.

The fix is to check for stored codes and test the engine charging system and battery function. Use an electrical starting and charging system tester to check for proper voltage and cranking current draw. Then repair the charging system, if necessary. Finally, install a replacement sensor using a new sensor assembly (Part No. 31935-3AX01).

I'm not an auto repair professional even though i have done some minor repairs before but i have checked the electrical system and it seems fine. Alternator is perfect, battery is fine. I did have a voltmeter connected while i cranked the engine over a couple of times and yes it did barely drop below 8volts 1 time. It's off and on, maybe 1 out of 5 starts it would go below 8volts.

Any ideas on which sensor they are talking about? I don't want to take it into the dealer just yet. I want to find out more before I do and just in case I might be able to switch the sensor out myself, or if it's even something else causing it to go below 8volts.


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