Did you try jumping the pressure sensor/switch?
I think its pin 43, not 34, for relay ground from pcm. And you don't have the ground signal, correct?
Quote:
When the vehicle operator makes an A/C request, a 12 volt request signal is sent out over the A/C request signal circuit and grounded through the PCM. When this request signal is grounded, the PCM can activate the A/C compressor clutch.
The PCM turns on the A/C compressor clutch by providing a path to ground through the A/C compressor clutch relay control circuit for the A/C compressor clutch relay. Power is provided to the A/C compressor clutch relay from of the underhood fuse block on the ignition 1 voltage circuit. Once the relay closes its internal switch, power from the battery is provided to the A/C compressor clutch through the A/C compressor clutch supply voltage circuit. Whenever the compressor is turned off, the A/C compressor clutch diode prevents a voltage spike from entering the vehicles electrical system. The ground circuit provides a path to ground for the compressor. The A/C compressor clutch relay control circuit is grounded internally within the PCM. On vehicles with the V8 option, an A/C compressor clutch status signal is sent to the PCM on the A/C compressor clutch supply voltage circuit.
The PCM will engage the A/C compressor clutch any time the engine speed is below 5000 RPM and the A/C is requested unless any of the wing conditions exist:
Throttle angle is at 100 percent (WOT).
Vehicle launch, hard acceleration from a stop.
Idle quality
The A/C refrigerant pressure sensor is above 2826 kPa (410 psi ) or is less than 207 kPa (30 psi ).
Engine speed is more than 5500 RPM .
Engine coolant temperature (ECT) is more than 121°C (250°F) for the L36 and 125°C (257°F) for the LS1.
Transmission shift
Engine torque load
Top of travel clutch switch position, if equipped
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