I have seen this many times. This alarm can occur if the tool changer forward/reverse or the drawbar clamped/unclamped switches are in the same state for a period of time.
Most repairs were switch related. They were out of adjustment.
I have seen a insufficient air supply (regulator pipe was clogged with scale and/or hose too small) cause the alarm. I watched the pressure drop and the drawbar come up working against the retention springs.
Broken spring washers in the drawbar causing drawbar to jam and not go all the way down.
Does it work with the button on the head?
Do you see an output to CR4 in the maintenance page?
Typically the solid state relays on the LCTLAUF go (short) and then the tool changer will not stop turning or has trouble going forward or reverse. If the solenoid is shorted it might take out one of these relays. Most relays have a resistance of 4 mega ohms across the 2 output pins. Anything less is usually a bad sign.
While there check that the arm on the motor is not loose and centered to the prox switches, the cam follower in the arm is not loose and the shock absorber is working.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)