DIRTY TRANSMISSION OIL .

As far as the oil light on at idle an going off with more rpm's , worn engine bearings , oil pump ! How many miles on it ? P1870 Chevrolet Transmission Component Slipping Look's like you need a new vehicle !

P1870 ! not P01870
DTC P1870 Transmission Component Slipping (Buick Built Before 6/17/97)
DTC P1870 Transmission Component Slipping (All Other Applications)
Circuit Description
The Powertrain Control Module (PCM) monitors the Torque Converter Clutch (TCC) slip by calculating the difference between the engine speed and the transmission output shaft speed.
If the PCM detects an excessive amount of slip when the TCC is engaged, then DTC P1870 sets. DTC P1870 is a type B DTC.

CODE P1870 - TRANSAXLE COMPONENT SLIPPING POSSIBLE CAUSE LOW TRANSMISSION FLUID LEVEL OR CONTAMINATED TRANSMISSION FLUID OR TRANSMISSION HAVE INTERNAL DAMAGE OR MECHANICAL FAULT.

well p1870 comes up as transmission component slipping i dont have p1850 in my manual but suspect it names the part problem.....

I also have a 99 Lumina and code p1870 means: Transmission Component Slipping/ Transmission Mechanical Transfer Case 4x4 Switch Circuit Failure Now we both know theres no 4x4 in these cars. So I'm going to try to find out about this and try to figure out why the PCM showed this code. When I do, I'll put it on my profile.

The code description for P1870 is "transmission component slipping" and usually means that the computer has detected a difference between what the input speed is and output shaft speed should be under certain conditions and tagged it as a slipping component. Usually it means that a clutch pack [usually direct drive clutch] or band isn't holding under a load and has started to slip. Sometimes the slippage can be observed on a scan tool during a road test but if the slippage is bad enough it may be noticable just driving it. Low transmission fluid level could cause this problem so make sure you check it before going any further. If it turns out that there is interal slippage then the transmission would have to come out and be repaired.

yes, when you burn your transmission fluid, its just like when you burn your motor oil. Lower vescosity means more friction. more friction, more heat, more heat messes with your sensors inside the trans causing them to send a code to the ecm. do a filter change and transmission flush. clear the code and retest.

check atf fluid.

P1870 is a code for a transmission component slipping. It would be very difficult to diagnose yourself. I suggest bringing it to a transmission shop.

code p 1870 refers to transmission component slipping
That can be from dirty oil or a clutch pack or band slipping or low oil pump pressure in the transmission
you say that it occurs on highway driving after 2 hours and that slipping will add friction heat to the transmission oil bringing on the oil temp light
take it to an accredited transmission professional service center that works on your make of vehicle , have the oil changed which require the pan removal
at the same time that will allow the adjustments to be done
when reassembled and refilled , have a pump pressure test done