For 1990-2009 cars

### 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) memory allocations.

The DTC P0601 sets when the RAM is not operating correctly when checked on initialization. An area of RAM is failed a read/write test.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0601 Transmission Control Module (TCM) Read Only Memory (ROM)

### Conditions for Setting the DTC

• | The EEPROM checksum test is separated in 2 independent parts, the code checksum test and the calibration checksum test. For each area the checksum is calculated and compared with the corresponding checksum valve. If the valves are different, the fault will be set.

• | 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 hold lamp will blink.

• | 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 valve.

### Conditions for Clearing the Hold Lamp/DTC

• | The hold lamp will turn OFF when the malfunction has not occurred after 3 ignition cycle.

• | 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 P0601 sets, the possible cause of fault could be the TCM.

#### DTC P0601

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Install the scan tool.
2. Turn the ignition ON, with the engine OFF.

Does the scan tool display P0601?

Go to Step 3

Go to Diagnostic Aids

3 |

1. Turn the ignition OFF.
2. Replace the transmission control module (TCM). Refer to Transmission Control Module Replacement .

Is the action completed?

Go to Step 4

--

4 |

1. Using the scan tool, clear the DTCs.
2. Road test the vehicle within the Conditions for Setting this DTC, as specified in the text.

Does the scan tool indicate that the diagnostic passed?

Go to Step 5

Go to Step 2

5 | Test to see if any DTCs are set. Are any DTCs displayed that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK