Code 61 - A/C System Performance (3.4L "F" Body): Notes

A/C refrigerant charge is calculated by inputs from the A/C refrigerant pressure and A/C evaporator temperature sensors. ECM will calculate system charge when the A/C is turned on. A/C evaporator temperature, A/C refrigerant temperature and vehicle speed are factored together to yield a minimum charge allowable for the A/C system to operate. If system charge falls below a given value for the temperature and vehicle speed variables, Code 61 will set. As ambient temperature falls, so does static (A/C off) refrigerant pressure. This produces a sliding scale which requires temperature, pressure and vehicle speed inputs to calculate a reliable system charge value that indicates when A/C refrigerant charge is too low to safely allow compressor to operate.

1. This test determines if code is intermittent and will also check A/C system for other failures. Repair all other codes before proceeding. Use appropriate A/C service manual to verify proper gauge readings. Pressures vary with temperature and humidity.
2. This test is to evaluate the A/C refrigerant pressure sensor for accuracy. A reliable gauge set should be used and no more than 20 psi difference in pressure between gauges and scan tester is allowable.
3. System is operating though Code 61 is intermittent. Hardware failures should be investigated using appropriate A/C service section.