DIAGNOSTIC RESPONSE:
Use default values.

CIRCUIT DESCRIPTION:
SAE J1708 defines the hardware and general structure of this interface, while SAE J1587 defines the format of data and messages used. This two-wire twisted pair datalink offers low speed communication (9600 baud) intended for basic information sharing and diagnostics, such as:

1. Engine information received by the Transmission Control Module (TCM) for shift modulation and clutch control, and
2. Transmission information sent to driver displays or instrument clusters.

Due to its slow baud rate, SAE J1587 is not intended for vehicle control purposes. A41 and A51 model TCMs do not have SAE J1708/J1587 support. The 9-pin diagnostic tool connector has SAE J1708 SCI High (+) signal available on terminal F, and SAE J1708 SCI Low (-) signal available on terminal G. Terminal 32 of the TCMs is for SAE J1708 SCI High (+). Terminal 72 is SAE J1708 SCI Low (-). W132 and W172 are a twisted pair.

CONDITIONS FOR RUNNING THE DTC:
After TCM initializes normally.

CONDITIONS FOR SETTING THE DTC:
DTC U0100 sets when the TCM detects needed messages, such as throttle % and engine torque, that have not been received via the SAE J1708/J1587 SCI for 2 seconds or more.

NOTE: MY09 and later calibrations that did not maintain autodetect, i.e. did not roll forward from earlier software, should not be reprogrammed by the CMC Override Throttle Source. This disables some datalink features for the calibration’s specified communication link type. If a different throttle source is needed, calibrate with a new CIN that enables the desired throttle source.

ACTION TAKEN WHEN THE DTC SETS:
1. The TCM does not illuminate the CHECK TRANS light.
2. DTC is stored in TCM history.
3. Default throttle percentage is used for shift scheduling.
4. The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
Use the diagnostic tool to clear the DTC from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without the DTC recurring.

DIAGNOSTIC AIDS:
DTC U0100 indicates that a SAE J1708/J1587 communication interruption has occurred. This code may be caused by:
1. Miswired of defective OEM controllers, OEM components, or OEM circuits attached to SAE J1708. These may include:
– Electrical noise.
– Bus-loading.
2. Defective TCM.

The diagnostic tool does not communicate over SAE J1708. Use Data Bus viewer from the file menu to determine if data is streaming over the SAE J1708/J1587 SCI.

Review applicable information in the OEM Technician’s Library, Control System and Transmission Specifications, and other related information.