Code 43 when it shifts into 2nd it falls on its face, unless you stomp on it. Service engine light is on computer is reading code 43

cam sensor codes

this code does not appear in the GM code list please contact the code reader manufacturer

Provide code for more info. jumping speedo could/would indicate speed sensor at the rear differential.

is the check engine on? are there any codes? sounds to be your 1st and 2nd shift solenoid is bad. the shift solenoids are in the transmission on the valve body

First is most auto parts stores will read the code for you for free--find out what the reason for the check engine light is first--where are you located?

When a 'check engine light' (MIL=Malfunction Indicator Lamp) is turned on, there is a DTC (Diagnostic Trouble Code) set/stored in the ECM/PCM (Engine Control Module/Powertrain Control Module). This code identifies which engine management system component/function experienced a malfunction. Once you pull/read this code, you may begin diagnosis.

Since the 'Check Engine' light flashed, and there were no codes stored (at least this is what the technician told you), there is definitely something happening with the engine computer. There is ALWAYS a code stored when the Check Engine light comes on - even if it's a 'History' code (unless there's a problem with the computer).

Have a qualified/certified Hyundai Service Technician properly diagnose this issue.

if you had the code checked then refuse to pay for this service unless they tell you what it means .This code is not in the toyota code read out

P0760....Shift Solenoid 'C'

but this is the nearest i can come up with with a generic code

2001 grand cherokee?
nor years of all parts swapped.
swaps are super complex topics, endless possibles.

dont expect magic from any TCM.
they cant tell you ever possible way things can be wrong
it will fail to shift right if things are wrong,
the trans TCM can go to limphome mode, read the service manual chapter 21 yet its free, posted here 300 times.
forget the silly engine , light (CEL) use only a scan tool one that can read all factory codes not some $20 tool.
CEL lamp is for failing smog. only. never trust it, if out.

i say bad shift solinoids.
the TCM can see late shift error.s but maybe not all.
stick in 1st is a hard failure.
all inputs to the TCM must be correct for the shift to 2nd happens.
check all inputs.
if those are then see if the TCM did shift to 2nd, but the solenoids ignored the logic inputs to the solenoids.
solenoids have many failure mods
dead. (stuck closed)
stuck open, valve open.
or leaking. (leaking can cause stuck in 1st and confuse any TCM)

leaking means breached, valve leaks where it must not. ever.

Have the tran fluid level checked