Circuit Description
The transmission control module (TCM) sends vehicle speed data to the engine control module (ECM). The data is sent to the ECM through a communication network called the controller area network (CAN). If the ECM receives invalid vehicle speed data from the TCM, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1504 TCM Communication Performance
Conditions for Running the DTC
| • | DTCs P1671, P1672, and P1673 are not set. |
| • | The ignition is on or the engine is operating. |
| • | The ignition 1 voltage is more than 10 volts. |
| • | DTC P1504 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
The ECM receives no valid vehicle speed data from the TCM for more than 1 second.
Action Taken When the DTC Sets
| • | 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. |
Conditions for Clearing the MIL/DTC
| • | 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. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Important: Record all Failure Records before clearing the DTC. Using Clear Info erases the Failure Records from the engine control module (ECM) and transmission control module (TCM). Did you record any TCM Freeze Frame/Failure Records? | Go to Step 3 | |
3 |
Did DTC P1504 fail this ignition? | Go to Step 4 | Go to Intermittent Conditions |
4 | Did any TCM DTCs or any other "U" DTC also set? | Go to Step 5 | |
5 | Test the controller area network (CAN) circuits in the wiring harness between TCM and the ECM for a high resistance, or for a poor connection at the module connectors, 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 7 | Go to Step 6 |
6 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | Go to Step 7 | -- |
7 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 8 |
8 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
