Originally Posted by RacinRust

This is from the GM electrical manual- - -
"When an electromechanical solenoid or relay is de-energized rapidly by a mechanical switch or semiconductor, the collapsing magnetic field produces a substantial transient voltage in its effort to disperse the stored energy and oppose the sudden change in current flow. These voltage spikes can occur at the positive terminal when the solenoid or relay is de-energized (keyed-off). If a solenoid or relay is wired onto the Run/Crank circuit of the vehicle to control aftermarket equipment, the spikes can be transmitted onto the circuit. The spikes can permanently damage the internal circuitry of the sensitive electronic components and/or control modules that are on this bussed circuit. To prevent damage to these components, the solenoid or relay MUST have the control circuit suppressed with a diode."

Originally Posted by PSM

That makes sense, thanks. The relay diagram below shows where I'd planned on wiring it in the relay. The switch is on 86 and 85 is grounded. 30 goes towards the ABS pump and 87 going towards the fuse box with 87a being unused. I would then put the diode before pin 87 preventing backflow going towards the fuse and whatever controls the ABS pump?