Circuit Description
A normal function of the transmission control module (TCM) programming is to perform an internal check that verifies the integrity of the random access memory (RAM) allocations.
The DTC P1604 sets when the RAM is not operating correctly when checked on initialization. An area of RAM is a failed read/write test.
Conditions for Setting the DTC
| • | An area of RAM is a failed read/write test. |
| • | The system voltage is too high or too low. |
| • | The transmission input voltage is too high or too low. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The TCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records buffer. |
| • | Adopt Emergency/Substitute mode and constant 4th gear by hydraulic control. |
| • | After ignition OFF/ON, 3rd gear by hydraulic control, and the positions, P, R, and N, are also possible. |
| • | Power supply cut off to the EDS valve. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF when the malfunction has not occurred after 3 ignition cycles. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | Use a scan tool to clear history DTCs. |
Diagnostic Aids
When DTC P1604 sets, the possible cause of the fault could be the TCM.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Automatic Transmission? | Go to Step 2 | |
2 |
Does the scan tool display DTC P1604? | Go to Step 4 | Go to Step 3 |
3 |
Is the action complete? | Go to Step 5 | Go to Step 4 |
4 |
Does the scan tool indicate that the diagnostic has ran and passed? | Go to Step 5 | Go to Step 2 |
5 | Inspect if any DTCs are set. Are any DTCs displayed that have not been diagnosed? | Go to Step 2 | System OK |
