Powertrain Controls - ECM/PCM

DTC 61 Chart A/C System Performance:

A/C System Wiring Diagram:

Circuit Description:

The ECM monitors A/C refrigerant pressure and A/C evaporator temperature to determine if the A/C system has adequate refrigerant (R134a) charge. The ECM will disable the A/C clutch whenever A/C refrigerant charge drops below a predetermined value, to reduce the chance of compressor damage.

The ECM determines A/C charge based on A/C refrigerant pressure and A/C evaporator temperature. The ECM uses these two inputs to calculate A/C refrigerant charge.

If the ECM determines A/C refrigerant charge to be low, the A/C clutch will be disabled and a Diagnostic Trouble Code (DTC) 61 will be set. DTC 61 will store in ECM memory, but will not turn "ON" the MIL (Service Engine Soon) light.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. DTC 61 could be caused by other DTCs, so refer to those charts before proceeding with this diagnostic chart.

2. If the A/C refrigerant pressure sensor is "slewed" or shifted in value, the ECM could be detecting a lower than normal pressure. Therefore, the ECM would be sensing a low refrigerant change and DTC 61 could result.

3. The conditions to set a DTC 67 could cause DTC 61 to set. DTC 67 will set if the ECM does not detect an A/C refrigerant pressure change of more than 4 psi when the A/C clutch is cycled from "OFF" to "ON."

4. The A/C performance test must be performed, because A/C system hardware (A/C compressor thermal expansion valve etc.) could cause a DTC 61.


Diagnostic Aids:

An A/C evaporator temperature sensor and/or an A/C refrigerant pressure sensor that is "slewed" (shifted in value) could cause a DTC 61.