Circuit Description
A normal function of the transmission control module (TCM) programming is to perform an internal inspection that verifies the integrity of the random access memory (RAM) allocations.
The DTC P1604 sets when the RAM is not operating correctly when inspected on initialization. An area of RAM has failed a read/write test.
Conditions for Setting the DTC
| • | An area of RAM has failed a read/write test. |
| • | System voltage is too high or too low. |
| • | Transaxle input voltage is too high or too low. |
| • | Immediately after the above condition occurs |
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. P, R and N also possible. |
| • | Power supply cut off to the pressure control solenoid (PCS) 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. |
| • | Using a scan tool can clear history DTCs. |
Diagnostic Aids
When DTC P1604 sets, the possible cause of fault could be the TCM.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Does the scan tool display P1604? | Go to Step 3 | Go to Diagnostic Aids |
3 |
Did you complete the replacement? | Go to Step 4 | -- |
4 |
Does the scan tool indicate that this diagnostic has run and passed? | Go to Step 5 | Go to Step 2 |
5 | Verify if any DTCs are set. Are any DTCs displayed that have not been diagnosed? | System OK |
