tRANSMISSION IS ACTING UP AFTER ERASING CODES

Replaced EGR gasket after trying to clean valve (EGR FLOW CODES) and erased codes.Short test drive and all seemed good so my daughter took it on home.Shortly she called saying the trans started acting as if it didn't want to stay in gear and would stop moving in gear.Could I have messed something up while removing the EGR valve, or erasing the codes? All was running fine when she left for home... Oh ,it;s a 99 Silhouette... Thanks for any advise..

Replaced EGR gasket after trying to clean valve (EGR FLOW CODES) and erased codes.Short test drive and all seemed good so my daughter took it on home.Shortly she called saying the trans started acting as if it didn't want to stay in gear and would stop moving in gear.Could I have messed something up while removing the EGR valve, or erasing the codes? All was running fine when she left for home... Oh ,it;s a 99 Silhouette... Thanks for any advise..
ok, checked codes and TPS code was on...un-pluged harness and pluged it back ,erased code and all was good again...May need to replace TPS or check for loose harness wire..