TCM - (Transmission Control Module)
P1921No bus data from ECM.
Fault symptoms
CHECK GEARBOX warning lamp is on.
TCM in Limp-Home mode.
Conditions
The TCM has had contact with the ECM at some time during the same ignition-on period
Fault criteria
If there has not been communication on the bus between the ECM and the TCM for more than 4 s a P1921 diagnostic trouble code is generated
Diagnostic help
See bus and diagnostic fault finding
Fault diagnosis procedure is not available.