Warning light comes on when accelerating from a stand-still in 1st / 2nd gear

most likely the light to tell you that the exhaust brake is in operation

whatever the reason for diesel in oil is harmful as the diesel makes the oil thin and loose its ability to lubricate the engine properly.
1st it can be overfuelling and that would cause that alot of black smoke coming out of your exhaust especially when accelerating hard
2nd it can be that the injectors are not sealing properly and dripping fuel while the engine not running

Governor pressure controls the 1st and 2nd shifts. After that is the 3 and 4 solenoids. you would need to look at the pressure when driving(takes a scanner). pressure is 20 to 30 PSI from 1st to 2nd, depends on acceleration. After that the pressure will jump to 100+ psi. Did you replace the governor solenoid and sensor? They are on the passenger side of the transmission and sit in a block that detaches from the valve body.

1 Ck A/T fluid level & quality
2 Scan/ck for code(s)
3 With scan tool connected,road test vehicle/Ck parameters....
....time for a pro !!

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Sounds like theres no 1st gear. Have you put the shifter in 1 and seen if it went, if so try 2-3 if it still accelerates slowly its probally stuck in 1st or 2nd gear, when it goes in to the 3 rd gear it will accelerate normally, also in 4th (OverDrive)

you either have a plugged fuel filter, a plugged converter or a bad mass air flow sensor

Sounds like you have a major misfire problem. The light is flashing because the ecm has determined that the problem is severe enough to cause damage to something. If your engine light flashes it is a warning not to drive the vehicle. I'm assuming this is a four cylinder. My guess would be that only two of the cylinders are actually producing any power. I would need the following details to help you further. How many miles are on this engine? Has the necessary factory maintenance schedule been maintained? In other words have the appropriate parts been changed and serviced to keep this engine performing properly. Many things could be causing your issues. Do the necessary maintenance first, like spark plugs and whatever the manufacturer requires and see what happens. If this does not help I can help you with the rest.

This is caused by a sticking or defective 2nd gear electric shift solenoid.
P0732 NISSAN - 2nd. Gear Malfunction
Symptoms - Engine Light ON (or Service Engine Soon Warning Light)
- Incorrect transmission shifting Possible causes - Low transmission fluid level
- Dirty transmission fluid
- Shift solenoids
- Transmission mechanical problems
- Transmission hydraulic control circuit

I think that this is the Lamda warning light which is an indication that the fuel / air mixture is not correct or the Lamda sensor mounted on the manifold is defective.

The blinking overdrive button is telling u that a serious fault has occurred in the electronic controls or a mechanical fault such as excess slippage is occurring.