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.
This diagnostic procedure supports the following DTC:
DTC U0101 Lost Communication With Transmission Control Module (TCM)
• | The ignition is ON. |
• | The DTC U0101 diagnostic runs continuously when the above condition is met. |
The engine control module (ECM) cannot communicate with the TCM.
• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
• | Clear the MIL and the DTC with a scan tool. |
The numbers below refer to the step numbers in the diagnostic table.
Step | Action | Yes | No |
---|---|---|---|
Is DTC U0101 present? | Go to Step 2 | ||
2 | Does the scan tool communicate with the engine control module (ECM) and transmission control module (TCM)? |