P1798 CAN TCM/INST Circuit Malfunction - 1997 Jaguar XK8

code p0700 refers to transmission control system/ MIL- malfunction===causes--wiring ---TCM replace the TCM
code p0750 refers to shift solenoid9SS) A-circuit malfunction===causes --wiring---shift solenoid ECM/TCM. When the TCM is replaced then it should be fixed as the TCM is common in both faults.

Trouble Code: P1684

Battery Has Been Disconnected

Possible Causes:


Quick Learn procedure was performed with scan tool.TCM battery direct (B+) circuit is open or disconnected.TCM power ground circuit is open.PCM/TCM was disconnected or it has been replaced.If you explain what you have been doing to your vehicle to get this code,it will make it easier to trouble shoot.

Coolant temperature sensor circuit malfunction.Or a faulty coolant sensor.

DTC P0705 - Transmission Range (TR) switch circuit malfunction (short to power supply)

DETECTION CONDITION
• Two or more range signals are input from the TR switch for 12 s or more.

Diagnostic support note:
• This is a continuous monitor (CCM).
• MIL illuminates if TCM detects the above malfunction condition in two consecutive drive cycles.
• PENDING CODE is available.
• FREEZE FRAME DATA is available.
• AT warning light illuminates.
• DTC is stored in TCM memory.

POSSIBLE CAUSE
• TCM malfunction
• Short to power supply in wiring harness between TR switch terminal A and TCM terminal 1D
• Short to power supply in wiring harness between TR switch terminal E and TCM terminal 2C
• Short to power supply in wiring harness between TR switch terminal D and TCM terminal 2B
• Short to power supply in wiring harness between TR switch terminal G and TCM terminal 2E
• Damaged connector between TR switch and TCM
• TR switch malfunction


Inspect swtich harnesses and test with OBD scanner reader tool.

The trans axle Control Module (TCM) monitors the malfunction of sensors and actuators relating to trans axle control. When the TCM detects a malfunction with the control, a signal is send to the Engine Control Module (ECM) to trigger the Engine Light or Service Engine Soon light. The ECM stores the P0700 code and it means the TCM detected a malfunction with the trans axle controls.
Possible Causes - Shorted or open circuit within transmission control module (TCM)
- Failure of trans axle control module
Since the P0700 is just and informative code, check the TCM for more codes to resolve the problem.
http://www.helpforcars.net/obd_codes/p0700_suzuki.html

P0700 JEEP - Transaxle Control System Malfunction
The transaxle Control Module (TCM) monitors the malfunction of sensors and actuators relating to transaxle control. When the TCM detects a malfunction with the control, a signal is send to the Engine Control Module (ECM) to trigger the Engine Light or Service Engine Soon light. The ECM stores the P0700 code and it means the TCM detected a malfunction with the transaxle controls.

Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Driveability problems
- Transaxle shifting problems

Possible causes
- Shorted or open circuit within transmission control module (TCM)
- Failure of transaxle control module

Tech notes: Since the P0700 is just and informative code, check the TCM for more codes to resolve the problem. So you'll have to have the dealer or another qualified shop/technician pull the transaxle codes from the TCM and go from there.

Good luck (remember to rate this answer)

P0750 has to do with the Shift solenoid A its a circuit malfunction. Could be related to or caused by the wiring, shift solenoid, or ECM/TCM.

P0755 is also a shift solenoid B issue Circuit malfunction. Possible causes are wiring, shift solenoid, ECM/TCM.

P0765 is also a fhist solenoid D issue Circuit malfunction. Possible causes are in wiring, shift solenoid or ECM/TCM.

Misfire could be result of not shifting right and making vehicle seem as if there is a misfire but only a suggestion. But either way sounds as if you need to consult with a shop that can run tests with computer on transmission issues first.

code po700 malfunction indicator lamp circuit malfunction tcm conditions. mil contoll circuit is shorted to ground .check the tcm for any codes in memory that are responsible for the request to turn on the mil lamp.tcm or trouble code malfunction has failed.

Transaxle Range Sensor Circuit Malfunction (PRNDL Input).  

Check for: _ Possibly a connector near the shift lever has come loose/dirty contacts, or there is a broken wire from it somewhere going to the TCM 
- Corroded or faulty Range Switch. - Open between Meter Fuse and Range Switch (C136-4).
- Open between Range Switch (C136) and TCM (C229) on one or more circuits. 
- Short to Battery between Range Switch (C136) and TCM (C229) on one or more circuits. 
- Short between two or more wires between Range Switch (C136) and TCM (C229). 

If Meter Fuse is blown, repair any shorts in the Meter Fuse circuit.

P1624 MIL Request Signal from TCM to ECM.This is only a request from TCM to ECM to turn the MIL on. The fault code is stored in the TCM.The Freeze Frame Data is stored in the ECM under the P1624 request code. Be sure to retrieve freeze frame data before clearing code P1624 from ECM. 
TCM = Transmission control module 
ECM = Engine control module (or more commonly known as ECU) 
MIL = Malfunction indicator light (more commonly "check engine light" or CEL) 

Good luck and hope this helps