1: DOn't believe all the codes for ahc. They are most of the time wrong or missing.
2: TC 31 is the front gate valve, which controls body roll in curves. Doesn't seem to have anything to do with your front being high and your rear being low.
TC 31 says "open or short in front gate valve". This can be checked with an ohm meter.
The front gate valve is a part of the ahc valve body; together with front levelling valve, and rear level and gate valves. It is located on the inside of the LHS frame rail, just forward of the accumulator (which is on the outside).
I think it is more likely that the cabling or a plug (e.g. in the dashboard) is at fault, than the actual valve body.
If the situation is that the rear is very low, it is most likely a height sensor fault, and they don't normally give any Trouble Codes.
Zeusv8 said:
Got the codes for the diagnostic
C1731 height control solenoid fr circuit malfunction /fr height 8.40mm/ fl height 6.60 and rr height -57.40
This indicates that the height sensor says the rear is 57.4 mm too low. If it isn't than for sure there is a height sensor, cabling or ecu problem.
Some illustrations: