Does the fan behind the radiator come on when you turn the A/C ON ? If the fan isn't coming on you'll overheat the engine and you won't get airflow to cool the A/C condenser while the car is stopped. If you post your email I will send you the shop manual instructions for troubleshooting the TRACS system, but its too long to post here (too many diagrams too).

DTC 4-2-4: TRACS PRESSURE SWITCH, OPEN OR SHORT CIRCUIT:

1) This DTC is set when control module senses pressure switch
has been shorted or grounded. Connect test box to control module. See
Fig. 3. Check pressure switch by connecting an ohmmeter between test
box terminals No. 13 and 26. Ohmmeter should indicate zero ohms.
Connect ohmmeter between test box terminal No. 26 and ground. Ohmmeter
should indicate no continuity.

2) If any reading is incorrect, check if wiring is broken or
shorted. If wiring is okay, replace hydraulic modulator. If readings
are correct, go to next step.

3) Connect an ohmmeter between test box terminals No. 13 and
26. Depress brake pedal. If ohmmeter indicates no continuity, ensure
brakelight contact is operating. If brakelight contact is okay, erase
DTC and test drive vehicle. See TEST DRIVING VEHICLE under DIAGNOSIS &
TESTING. If DTC reoccurs, replace control module. If ohmmeter
indicates continuity, check wiring for a short circuit. If a short
circuit is not present, replace hydraulic modulator.


Mike