Diagnostic Instructions
DTC Descriptor
DTC P1601: Lost Communication with TCM.
Circuit/System 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.
Conditions for Running the DTC
| • | The engine is running more than 2 seconds. |
| • | The ignition 1 voltage is more than 11 volts. |
| • | 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
DTC P1601 is a Type B DTC
Conditions for Clearing the DTC
DTC P1601 is a Type B DTC
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Circuit/System Verification
Start the engine, observe the DTC information with a scan tool. DTC P1601 should not set.
Circuit/System Testing
- Ignition ON, attempt to establish communication with the TCM with a scan tool.
- Ignition OFF, disconnect the harness connector of the TCM.
- Ignition ON, verify that 1.5-3.4 volts is available between the CAN serial data low and the CAN serial data high circuits.
| ⇒ | If the voltage is not within the specified range, replace the TCM. |
- Ignition OFF, test the CAN communication circuits between the ECM and the TCM for an open, short to ground, or a short to voltage.
- If the circuits/connections test OK, replace the ECM.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
Control Module References
for engine and transmission control module replacement, setup, and programming.
