my sister has a 07 uplander with the 3900 in it and the check motor light is on, however when we scan it the tool says ecu not detected, same thing with 3 diffrent scan tools, any help here will be awsome, the van has 110,000 on it so its out of warrenty also the fuel gauge will say like 300 than when u turn it off and start it ul get low fuel, than turn it off and start and ull get like 250

 

Welcome to the forum. The scanners are probably not seeing the battery voltage on the DLC connector pin 16. Check the 10A OnStar fuse in the I/P fuse block?

 

ill check it out in the morning, is that the fuse block on the passanger side?