Circuit Description
Modules that are connected to the shared communication circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have pre-recorded information about what messages are needed to be exchanged on the serial data circuits for each virtual network. The messages are usually supervised and some periodic messages are used by the receiver module as an availability indication of the transmitter module.
DTC U0401 TCM received invalid data from ECM
Conditions for Setting the DTC
The transmission control module (TCM) detects an invalid throttle position signal, engine speed signal and/or engine coolant temperature signal for more than 2 seconds.
Action Taken When the DTC Sets
• The TCM will store the DTC when a failure is detected on the first ignition cycle.
• The TCM will illuminate the HOLD lamp.
• The TCM can no longer determine the validity of any information it may or may not receive from the engine control module (ECM). Therefore the TCM substitutes default values for engine speed, throttle position, and other engine data signals.
• Transmission operation will be reduced, affecting shift points, torque converter clutch operation, and other driveability concerns.
Diagnostic Aids
• An intermittent malfunction may be caused by a fault in the electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions in Engine Controls 1.6L.
• Repair any electrical circuit faults that were found. Refer to Wiring Repairs in Wiring Systems.
• Faulty ECM and/or TCM
Install a scan tool.
Turn ON the ignition, with the engine OFF.
Save the DTC and Freeze Frame information into the scan tool memory.
Perform the scan tool Clear DTC Information function for the transmission control module (TCM) and the engine control module (ECM).
Operate the vehicle for 1 minute or until the MIL illuminates.
Check the TCM for DTCs.
Is the Malfunction Indicator Lamp (MIL) On?
--
YES - Go to Step 2
NO - Repair the wiring connectors for intermittent failure
Select request DTC status from the Diagnostic Trouble Codes Information menu
Request DTC by status
Is DTC U0401 displayed?
--
YES - Go to Step 3
NO - Repair the wiring connectors for intermittent failure
3
Turn OFF the ignition.
Disconnect connector A from the TCM.
Turn the ignition ON, with the engine OFF.
Measure the resistance between terminal A17 of the TCM wiring connector and terminal K14 of the ECM wiring connector.
Measure the resistance between terminal A7 of the TCM wiring connector and terminal K15 of the ECM wiring connector.
Was the resistance the specified value for both circuits?
0 ohms
YES - Go to Step 5
NO - Go to Step 4
401 views
Usually answered in minutes!
×