This is a 2002 Ram 1500 4X-5.9L. Background is it sets P0748 (has been happening for over a year)and goes into limp mode. Owner replaced solenoid, no change. Took it to a trans shop, they rebuilt trans and put in another new solenoid. Code returned immediately. Trans shop said it is electrical not trans problem. I made basic tests then connected scope with amp clamp (blue)and voltage probe(red) to pressure solenoid control lead . Readings taken at the PCM with the engine idleing in Park. Code will set, repeatedly, with those conditions. The anomaly, I think, is that the PCM pulls the lead to gnd, infrequently, for about 500ms. The solenoid is 3-6 ohms(spec) so the 3A is normal for full ground application. What I am unsure of is that a normal operation or not? I think not but don't have anything better than thinking to back it up. The P0748 is a circuit code(not operation related) so, I don't think that it is caused by a pressure sensor correlation. ( The pressure sensor does show activity.) I don't find a specific criteria for setting the code. [trans pressure solenoid]

[2002 Dodge Ram 1500 SLT, Transmission Waveform]

Steve Park
Technician
Public Safety Radio
Gallatin, Tennessee, USA

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