Strange Issues after logic board replacement

Hi,

After logic board failure, unknown reason but possible overheat? bad GPU. (wouldn't boot, 3 seconds fan, optical and HDD noise, light blink then off) I decided to replace logic board with one out of redundant system.

Followed tear down guide, new thermal paste, all screws went back in macbook booted first time as soon as I put the power lead to the connector ( I thought nothing of this the first time).

Upon testing I have discovered the following.

1. After removing DC power cable (i am running without battery as its swollen) and putting back in mac starts up on its own. (after !@#$ down and without disconnecting DC macbook shuts down and only restarts on button press).

2. Does not remember time and date or wifi password.

3. After running hardware test following error:

4SNS/1/40000001:TGOH - 0.000

So far I have done the following:

1. Installed istat pro and SMC fan control. I have temp readings for all sensors and they all seem reasonable, when ramping up fan speeds temps drop. The fans are not running overtime as they do for some people and applications seem to be behaving apart from a few crashes of safari recently.

Idle GPU diode = 56 (Degrees C)

Idle CPU = 48

Heatsink A = 48

Heatsink B = 38

Heatsink C =41

2. Opened case up and re-seated connectors for sensors, tested PRAM battery, reading 3.06v. tested connections across logic board from -ve battery to +ve solder point on logic board (through the connector clip on board to ensure good connection) and reads 3.06v. Switching to +ve battery and -ve solder point reads 0.00V. I presume this is because current dissipates along the board somewhere.

3. Reset PRAM and SMC.

4. Ran disc utility and fixed permissions.

5. Searched for similar issues

My question is: can the (possibly) faulty sensor be causing PRAM issues or could the replacement board be damaged?

After disconnecting all power, the system chime does not reset to default volume and stays at whatever the last volume setting was (unless reset PRAM) which makes me think that the PRAM battery is fine and is retaining some settings.

Could this be a result of not routing some of the connectors properly after reassembly?

Many thanks for any help.