Can someone tell me what would cause a code 27. I just had a new computer installed, no codes then. Today I replaced the starter and got a code 12 and 27. Any ideas?? Thanks in advance.

 

Code 27 indicates the computer sensed a problem with a fuel injector.

Try resetting the computer (disconnect the battery for at least 30 seconds).
With the battery disconnected, unplug the electrical connector at the computer, inspect the pins for corrosion, damaged pins, loose pins, and broken wires.
Look at the wires leading to the fuel injectors (one per cylinder) for any abnormalities.

Reconnect the computer, and before starting the truck again, check the codes. (Should get code 12 and 55, these are nothing to worry about)
Than, just monitor to see if code 27 comes back. If it does, further digging will be required.

 

When I left the shop after they installed the new computer the truck was running good with no check engine light coming on. I took it home put it on ramps and changed the starter. Then the check engine light came on. Could I have done something to cause this? All the work I did was under the truck except for disconnecting the battery while I removed and installed the new starter. Thanks for the info.

 

Try resetting the computer as I said, than, before starting the truck again, check codes. See if the code comes back.
It could like the a fluke that the code came on.