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Discussion Starter · #1 ·
Can anyone point me in the right direction or to a resource that helps us learn how to use the live data of OBD2 scanners?

The transmission cycles through all the gears when no load, but starts slipping when a load is applied. It previously threw a code p0756-39 but has not thrown the code since I cleared it despite trans still slipping when a load is applied.

I've been playing around with an OBD2 scanner collecting live data and doing activation tests. I can hear a click when I toggle each shift solenoid on/off but this doesn't tell me if they are leaking.

When I used the OBD2 scanner to cycle through the gears, I could hear a solenoid click when I went from 1-2, 3-4, and when I downshifted from 3-2 and 2-1. There was no click when shifting 2-3 or downshifting 4-3.

Live data says:
gear 1 = 1-2 on, 2-3 on, 3-2 off
gear 2 = 1-2 off, 2-3 on, 3-2 off
gear 3 = 1-2 off, 2-3 off, 3-2 on
gear 4 = 1-2 on, 2-3 off, 3-2 on

I have collected and saved lots of data but don't yet know what is relevant.
 

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Discussion Starter · #2 ·
I should give more background. Transmission ran really well. No sign of a problem. Then suddenly van started running really ****ty, limped along a bit and then died. Distributor rotor had come loose and was bouncing around. I replaced cap/rotor and van ran again. However, it lacked power when under load.

I've been operating under the belief that there is a good chance I'm dealing with an electrical issue triggered by massive uncontrolled sparks cause by loose rotor. But where and how to look.
 

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Sounds like a main line pressure problem. Test main line pressure is my suggestion. Is trans full of oil? The DTC you have P0756 is a solenoid B code. Even with that code the transmission should move correctly , not slip.
 

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Discussion Starter · #4 ·
Sounds like a main line pressure problem. Test main line pressure is my suggestion. Is trans full of oil? The DTC you have P0756 is a solenoid B code. Even with that code the transmission should move correctly , not slip.
Thanks. I'm still learning the nuances. Yes, trans is full of oil. First thing I did was a fluid/filter change to get an idea of overall tranny condition. The fluid was discoloured with a amber hue, but not black or burnt. It didn't feel gritty and there was not much sediment in the pan or on the magnet. Determining the right level isn't easy. I'm finding it hard to see the oil on the dipstick. Sometimes it looks over filled, and then other times it seems right. I wish the tranny had an overflo plug that would allow excess fluid to drain.

Next on list is to test main line pressure. Not sure how to do that under load yet.
 
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