Check engine light / computer reprogram / MPG change

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[Kingsfr]

About 3 weeks ago the check engine light came on. I brought it to the dealer. They told me that the codes were showing misfires, but there wasn't any real misfires. The engines computer just needed to be reprogramed. OK...not a big deal. The codes read were: P0300, P0301, P0303 & P0306. "Refer to TSB PI0473. Performed engine control module calibration software update."
Well, the check engine light went out and has not come back on. However, my fuel efficiency has decreased by a full 1 MPG. Now, if I was getting decent MPG's I wouldn't care so much, but I am one of the Acadia owners who get poor MPG's. I used to get 16 MPG. Now I'm getting 15 MPG.
Has anyone else had their computer reprogrammed and experienced a change in MPG ( + or - )? Does anyone know if there is a way to reprogram the computer to increase fuel efficiency? Will returning to the dealer do anything?

[mikemu]

About 3 weeks ago the check engine light came on. I brought it to the dealer. They told me that the codes were showing misfires, but there wasn't any real misfires. The engines computer just needed to be reprogramed. OK...not a big deal. The codes read were: P0300, P0301, P0303 & P0306. "Refer to TSB PI0473. Performed engine control module calibration software update."
Well, the check engine light went out and has not come back on. However, my fuel efficiency has decreased by a full 1 MPG. Now, if I was getting decent MPG's I wouldn't care so much, but I am one of the Acadia owners who get poor MPG's. I used to get 16 MPG. Now I'm getting 15 MPG.
Has anyone else had their computer reprogrammed and experienced a change in MPG ( + or - )? Does anyone know if there is a way to reprogram the computer to increase fuel efficiency? Will returning to the dealer do anything?

15MPG in city driving?  Hopefully that's not highway.

[rbarrios]

2010 - 2011
 Acadia, Enclave, Traverse -- MIL encendida después de un arranque en frío con conteos de fallo de arranque aleatorios
 Reprogramación del vehículo
 Reemplace los inyectores, ECM, bujías
 PI0473
 

2010 - 2011
 Acadia, Enclave, Traverse -- Témoin d'anomalie allumé après un démarrage à froid et ratés aléatoires
 Reprogrammer le véhicule
 Remplacer les injecteurs, les ECM, les bougies d'allumage
 PI0473
 
2010 - 2011
 Acadia, Enclave, Traverse -- MIL illuminated after cold start with random misfire counts
 do this---Re-flash vehicle
 dont do this---Replace injectors, ECMs, spark plugs
 PI0473
 

[MA Acadia]

I had my ECM updated a few months ago to fix a transmission shift problem ( didn't really notice a change with shifts after the update ) and it didn't seem to change my MPG. The update will cut in half your miles between oil changes as before the update the oil life moniter would have me go about 10K before it would be down to zero life, now it will hit zero life at 5K miles. ( I always changed it at 5K miles as I only put 5k miles per year so I change it once a year ) If you mentioned to the dealer that you had roll back in gear he may have installed a updated to resolve that but would affect your MPG. I ran my VIN on the website   http://tis2web.service.gm.com/tis2web and looked up ECM firmware and it shows two calibrations ( firmware ) for the ECM, the bottom one ( see below information ) will decrease your MPG and they both will get rid of the codes you had. Try running your VIN at the website and see what you come up with and maybe check if the dealer installed the wrong firmware on yours.



M4455: There are 2 calibration part numbers that are valid for 'Engine Operation'. Read the descriptions from the following tables to determine the correct calibration for this vehicle.
Calibration History for: Engine Operation
Part Number  CVN  Bulletin #  Description 
12649497 7717634B -  DTC P0300 cold start, low ambient temperature, low misfire counts, first 60 seconds.
12645934 C7444F7D -  New calibration to enhance the operation of the engine oil life monitor to more accurately identify the required oil change interval.
12643741 CE78CBB0 -  New calibration to enhance the operation of the engine oil life monitor to more accurately identify the required oil change interval.
12637011 00986382 -  New calibration to improve cranking and starting.
12636081 478BC8BA -  New calibration with diagnostic enhancements for DTC P0690.
12635286 AD6E9FF4 -  Incremental Release RPR1.
12621154 4CBF8AA1 -  Engine Operation

Part Number  CVN  Bulletin #  Description 
12649498 5A595255 -  DTC P0300 cold start, low ambient temperature, low misfire counts, first 60 seconds.
12645935 0CF6312E -  New calibration to enhance the operation of the engine oil life monitor to more accurately identify the required oil change interval.
12643742 F8941BCC -  Select this calibration only to address customer compliants of vehicle roll-back on slight grades. May cause additional vehicle creep on flat ground, increased power steering noise and a slight reduction in fuel economy.
12637011 00986382 -  New calibration to improve cranking and starting.
12636081 478BC8BA -  New calibration with diagnostic enhancements for DTC P0690.
12635286 AD6E9FF4 -  Incremental Release RPR1.
12621154 4CBF8AA1 -  Engine Operation
 
 

[Kingsfr]

15MPG in city driving?  Hopefully that's not highway.

Mixed. Maybe a little more Hwy than city.

[Kingsfr]

MA,
Thanks for the info.