Test M: No Universal Asynchronous Receiver-Transmitter (UART)-Based Protocol (UBP) Network Communication
PINPOINT TEST M: NO UNIVERSAL ASYNCHRONOUS RECEIVER-TRANSMITTER (UART)-BASED PROTOCOL (UBP) NETWORK COMMUNICATIONM1-M2:
M3-M6:
M6-M9:
M10-M14:
M14-M16:
M17-M18:
Normal Operation
The driver climate control seat module, passenger climate control seat module, electronic automatic temperature control (EATC) module, and the driver seat module (DSM) communicate with the diagnostic tool through the UBP communications network, circuit 2077 (PK/LB). If the UBP circuit is open, communication to the module in question is not possible. If the circuit is shorted to ground or shorted to voltage, the entire network goes down and communication to all modules is not possible. Check circuit 2077 (PK/LB) between the driver climate control seat module, passenger climate control seat module, EATC module, DSM and the data link connector (DLC) C251. The total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is either an open in circuit 2077 (PK/LB), damage to the DLC C251, damage to one of the networked modules, or a problem in one of the in-line connectors. If, after individual checks of each circuit leading to a module show resistance values less than 5 ohms, and no in-line connector issues are present, the data link diagnostics test must be run with the module in question disconnected. If the data link diagnostics test passes with the module in question disconnected, it is the source of the concern and should be removed and a new module installed.
Possible Causes
- UBP circuit 2077 (PK/LB) open, short to ground or short to voltage
- driver climate control seat module
- passenger climate control seat module
- DSM
- EATC module
- DLC C251