Auto transmission will not engage in DRIVE gear when starting.

There isn't a code P01871 , nor P1871 . DTC - P1870
The powertrain control module (PCM) monitors the difference between engine speed and transmission output speed. In D3 drive range with the TCC engaged, the engine speed should closely match the transmission output speed. In D4 drive range, with the TCC engaged, the TCC slip speed should be -20 to +50 RPM.
When the PCM detects excessive TCC slip when the TCC should be engaged, then DTC P1870 sets. DTC P1870 is a type B DTC.


Your best bet ,take your vehicle to a qualified repair shop.
Bronze material found in the transmission oil pan may indicate stator shaft bushing wear. If bushing wear is suspected, inspect the stator shaft and the input, turbine, shaft for damage.
• Refer to Symptoms - Automatic Transmission for more information.

any codes or service eng lite?

if the fluid is to low it will not engage

The weld on the manual lever is known to break loose. First, with the wheels off the ground, with the lever in the park position, does the drive shaft lock in park? If yes or no sometimes, drop the trans pan. I bet the nut on the lever camd loose.

change fluid and filter

Does the starter engage the drive gear with the action of a solenoid? It may not be pushing (pulling) the gear far enough. There may be a slipping ring gear on the flex-plate. If you pull the starter again, you can try to see if the ring moves in and out or appears to be slipping around on the flex-plate. The flex plate could be loose on the crankshaft. In any case, the engine or the transmission would have to come out. Check the starter engagement before removing the torus and flex-plate.

auto trans operates on fluid pressure. if the trans has never been serviced, more than likely the filter is plugged, and or the fluid is bad. no doubht its burned and will smell and look like it. get it towed to a shop and have the fliud and filter changed first, then check the band adjustment.recommend a trans shop do it and not jiffylube.

Howdy, My name is Mark, I am a mechanic (Auto trans and Diff specialist 23 years) this symptom is common with a broken driveline component, with full time 4WD and centre diff all the drive goes to the wheel with least resistance, (or to broken component) therefore when you engage difflock (Center) the drive then goes 2 ways front and rear so vehicle will drive, could be as simple as stripped spline in front wheel hub, broken CV joint etc. 1 major weakness these vehicles have is if driven with center diff lock engaged on high traction surfaces they do break the front diff, this will give the same symptom but you would of been aware of it when it happened.
To check where the drive is going chock all 4 wheels, park brake on, bonnet up, start engine let it idle down (after cold start), engage reverse (high range open center) from the front of vehicle and off to one side you can see the front axles, if one of them is turning that is where your drive is going, have someone to help you and under no circumstances place your self under or in driving path of vehicle.
Hope this helps

Not a computer issue. Transmission has problems could be filter stopping up, which also means problems.