DTC U1016: Loss Of Pcm Communications (ALERO, 1998 Century, 1999 Grand Am, Intrigue & Regal)

1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK. After performing diagnostic system check, go to next step.
2. Perform PCM ON-BOARD DIAGNOSTIC SYSTEM CHECK. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If on-board diagnostic system check passes, go to next step. If on-board diagnostic system check does not pass, go to appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
3. Turn ignition off. Install scan tool, Turn ignition on, with engine off. Attempt to establish communication with PCM. If communication can be established with PCM, go to next step. If communication cannot be established with PCM, diagnose serial data line. See appropriate diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.
4. Malfunction is not currently present. When DTC U1016 is current (malfunction in Purple wire or Light Blue wire circuit), no communication can be established with PCM. When malfunction is present, DTC U1016 will be stored in system memory. Before performing diagnostic testing for DTC U1016, perform PCM on-board diagnostic system check to eliminate possible faulty PCM. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

An intermittent may be caused by a poor connection, rubbed through wire insulation, or a broken wire inside insulation. Frequency of malfunction can be determined by using enhanced diagnostic function of scan tool. Check for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wiring connections, or damaged wiring harness.