check engine light and loss of brake pedal

Thank you all.

Two different Safaris that I have had were of the same vintage as yours. Your comment about working on the batteries really rings a bell. Safari was real good at connecting both positive and negative smaller gage wiring to terminals on the batteries (both house and chassis). When changing batteries or cleaning terminals or doing other chores where wires were disconnected it was real easy to lose a wire or two over behind the battery drawer. It is really important to mark these wires when you take them off as to terminal type, Plus or ground. If you don't you will need to wring them out before reconnecting so you don't get them in the wrong place. As far as the brake problem is concerned I think that is a separate issue.

IMHO 2-unrelated problems. Remove master cylinder cap. Submerge finger into master cylinder which of course has not lost fluid. Rub bottom of reservoir. Remove finger. Looknat tip. Is it black? If YES master cylinder seals have decomposed..time to replace. Check calipers, wheel cylinders, and every hose on the unit. If fluid level is low do. Ot rule out a master cylinder.power brake diaphram leak. Maybe it's time for a pro to take over.

Brakes are hydraulic but not sure if rear are disc. I noticed the soft brakes before the light came on and loss of power.
yes problem started after working on batteries.
No the engine does not quit just reduce power.
I will try going over all connections again. thank you.

I sounds like you have a bad battery connection somewhere. I would clean all connections, inspect terminals for corrosion, and reinstall.

We are probably going to need more information to give you good advice:

Assume your brakes are hydraulic over hydraulic 4 wheel disk brakes-- please confirm.

Assume that this problem only began after you worked on the batteries-- please confirm. If so, I would sure go over all the connections, including some of the smaller-gauge ones.

Does the engine quit (i.e. tach goes to zero) when this happens or does it just have reduced power?

The brake problem is a bit puzzling (assuming it is the system I mention). Even if the engine quits, you have an electric back up on the master cylinder to provide boost were the engine to stop. This is boost only-- totally separate from the brake hydraulics. The fact that you have to pump the brakes suggests that the brake (vs boost) portion of the system has a problem. Problem could be bad master cylinder or air in the system. Can't see how lack of boost would give you a soft pedal where you have to pump to firm up.