New engine in and running but throwing codes

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.

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?

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

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

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...

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.

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

New problem:

Waterneck/thermostat leaking at the seam.

Is this a dealer-only part?

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).

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

everything is grounded, engine block, tranny case and exhaust manifold all have continuity

Unfortunately it's difficult to test an o2 sensor without a known good one around for a baseline reading. If you have a known good one, swapping them out takes all of 5 minutes.

If that's not the case (I've never encountered that code and had it been the o2 sensor). My next guess would be the ignition system not functioning properly. I would find a shop that has proper diagnostic equipment (oscilloscope) and have them see if the coil is jacked or something.

TFT sensor is the Transmission Fluid Temperature sensor. They go bad pretty often in transmissions and are known to cause misfires (In a Ford Tempo anyway).

hmm might check that then...

Hey what motor did you put in? What happened to your old one?

P0300 is sometimes difficult to resolve. I have never heard of it being related to the O2 sensor, as there are many O2 specific codes that would come up. I would lean more towards ignition as has been mentioned - check coils, wires, and plugs (check the gap too). Also I had a camshaft position sensor go bad on me, and it also caused intermitent misfires.

any updates?

haven't touched it for a couple of weeks. i just got the new water neck in the mail on wednesday and will probably start on it tomorrow. i have a feeling that i may have to bite the bullet and take it to a dealership if i can't figure it out by next weekend.

Anything new with this? ..... see my previous post on 1st page

Got it going! I made friends with a tech at the local dealership who hooked the Aveo up to the computer for free. Had an open ground on the transmission and a bad connection on the cam position sensor. I cleaned and tightened up the ground and replaced the connection on the cps with butt connectors, as instructed by the tech. Cleared out the code and 300 miles later, its running great!
Mileage is lower than expected on the 1st tank, got about 26.5 to the gallon.

Next, I need to flush the cooling system

Great to hear! Congrats!

Quote:

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Originally Posted by fourbi4rox

Got it going! I made friends with a tech at the local dealership who hooked the Aveo up to the computer for free. Had an open ground on the transmission and a bad connection on the cam position sensor. I cleaned and tightened up the ground and replaced the connection on the cps with butt connectors, as instructed by the tech. Cleared out the code and 300 miles later, its running great!
Mileage is lower than expected on the 1st tank, got about 26.5 to the gallon.

Next, I need to flush the cooling system

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thats the mpg i get in the city when i dont accelerate modestly