Circuit Description
The controller area network (CAN) serial data bus is used by the engine control module (ECM) and automatic transmission control module (TCM) to share information. An example of information shared is engine speed, engine coolant temperature, manifold absolute pressure (MAP), throttle position and vehicle speed.
If the ECM does not receive a message from the TCM, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1601 Lost Communication with TCM
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The ignition voltage is more than 11 volts. |
| • | The engine is running more than 2 seconds. |
| • | No output controls are active. |
Conditions for Setting the DTC
The ECM does not detect a valid message from the TCM.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the MIL after 3 or 4 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. |
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |||||||
2 |
Did the DTC fail this ignition? | -- | Go to Step 3 | Go to Intermittent Conditions | ||||||
3 | Attempt to establish communication with the transmission control module (TCM) with a scan tool. Does the scan tool communicate? | -- | Go to Step 4 | Go to Scan Tool Does Not Communicate with Component in Data Link Communications | ||||||
4 |
Is the voltage within the specified range? | 1.5-3.4 V | Go to Step 5 | Go to Step 6 | ||||||
5 | Test the CAN serial data high and low circuits for the following:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 | ||||||
6 | Test for shorted terminals and poor connections at the TCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 | ||||||
7 | Test for shorted terminals and poor connections at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 | ||||||
8 | Replace the TCM. Refer to Transmission Control Module Replacement in Automatic Transmission - Aisin (81-40LE). Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
9 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
10 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 11 | ||||||
11 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK |
