check engine light/gas milage??

I have a '01 V6 king cab 4/4 with 148,000 miles on it. The dealership just did the timing belt, water pump, belts, fuel filter, pcv valve and plugs. Truck ran great-70 miles later the check engine light came on. they said it needed a air/fuel sensor. Changed a/f sensor-light still on. faulty a/f sensor-put in new one. light still on. Dealership said now it needed a new ECU-I had my ECU refurbished(299.00). Check engine light is off but my milage has gone from 19/21 to 14 MPG. Anyone have any Ideas????????? Thank you!!

 

try disconnecting the battery. It will re-boot the ECU which would reset four air/fuel mixture

 

Are you saying flash the ECU? Lights on,disconnect the - termanal,leave off for 1/2 hr, reconnect? do all this with the lights on-ingnition off?

 

never heard of having to have the lights on. seems kinda dangerous, the spark you'd get when you reconnect the battery terminal.

in any case disconnect the battery for about a half an hour, reconnect it, and drive it like you normally would. be aware it's gonna act funny for a little while during its re-learing period.

i know for sure you don't have the key on while you do this. my haynes says that alone can cook the ECU.

 

thank you!