New engine in and running but throwing codes

[fourbi4rox]

I finally got the engine in, fired it up and everything looks and sounds great! Initially, there was no check engine light on, then I took it for a spin and less than 100 yards later, its flashing the check engine light. Here are the codes:

P0300- random cylinder misfire
P0700-transmission control computer malfunction
P01781- TFT sensor malfunction

Everything looks and sounds great, runs strong, shifts good, no overheating or leaks, no knocking.

Any Suggestions? I'm terrible with this electronic/computer stuff.

[xtreme 2]

Random Cylinder Misfire is 9 times out of 10 the o2 Sensor...

Transmission control malfunction, did you remember to plug the computer for the tranny into the plug it goes into?

not sure what the TFT Sensor is...

It is most likely going to relate back to wiring... something that wasn't hooked up properly... or maybe your grounds. Make sure the tranny and engine are both grounded properly...

did you do it yourself or have a shop do it?

[xtreme 2]

btw if I fix your problem you should give me those parts free

[fourbi4rox]

Thanks for the help. Tell u what, I'll cover your shipping if you are right! How do I check the O2 sensor?

[xtreme 2]

I'd start by looking and making sure it is plugged in... After that, unscrew it and see if it is black. Unless you have a crate motor, there is a possibility there were carbon deposits and they caked the o2 sensor when you drove it the first time...

[fourbi4rox]

Not a crate motor, came out of a wrecked car.

Can't find any loose wires, all the grounds in the engine compartment bolt on the lower starter stud, which is tight.

o2 sensor isn't dirty, tried the one from the other manifold I had and still no success.

[xtreme 2]

There has to be a ground on the tranny...

[fourbi4rox]

New problem:

Waterneck/thermostat leaking at the seam.

Is this a dealer-only part?

[exodus]

make sure to check the ground continuity or voltage. Using a voltmeter, put one test lead on the engine block or exhaust manifold (the entire tranny case should be a good ground, as well) and the other on a known good ground or + lead. It should read 12.whatever with the engine off.

Definitely check the exhaust manifold for voltage. I'm not positive, but the o2 sensor may use it as a ground.

Thermostat/Housing/seal can be purchased from gm-car-parts.com for around $25 shipped. If it still looks like it's leaking afterwards (and you're positive the thermostat and seal are in properly), it could be your waterpump spraying coolant all over (personal experience).

[fourbi4rox]

tstat housing is cracked at the seam, just ordered one, $22 shipped. Thanks!