Diagnostic Aids

If DTC P1626 and U1064 are set together, a problem most likely exists on the Class II link or information is being interrupted. Interrupted information can be caused by the BCM intermittently losing its power/ground circuit. If BCM intermittently loses the power/ground circuit, scan tool will lose communication with that module. Other modules may also set a lost communication with BCM DTC as well.

Class II link is in ring configuration. Two opens, one at each end of BCM need to be present for PCM to lose communication with PCM. If a short to ground or short to voltage on Class II link exists, communications between all control modules will be lost and PCM should set DTC U1300 or U1301.

If DTC P1626 sets by itself (no "U" type DTC set), the most likely cause is that the BCM is not sending the PCM any fuel decision password. If both controllers communicate with scan tool, BCM is most likely at fault.