I need to ask the question once again as the car I have is a Toyota Corolla Spacio 2001 model. The engine will suddenly cut out going at any speed but will then restart very easily if the ignition key is turned off and then restarted. I notice that the only gauge to react is the temperature gauge which drops to zero. My mechanic has checked the car using a computer and can find nothing wrong. Any ideas?

SOURCE: Voltage Gauge drops suddenly to zero

Charging system grounding out, poss inside alternator

SOURCE: GAUGES GO CRAZY AND SOMETIMES VEHICLE WON'T START

Poor grounding can cause many of the conditions you have listed. When checking power with a volt meter, this goes unnoticed because the meter does not draw enough amperage to cause the bad connection to break contact. Your battery is grounded to the engine block and also has a small lead to the fender. Many components have individual ground leads as well (including most computers) I would check all ground leads and clean the contact surfaces with sandpaper or a wire brush. Adding an additional ground wire is a good idea as well. Don't forget that the dash board frame must also provide a good ground as well.
Many times this is all you need to do...sometimes though, control modules can be damaged because in having a partial ground, they build up heat, due to additional resistance in the circut.
This may or may not cure your problem, but it's worth checking out. Grounding is often overlooked, especially if it has not completely broken down.

SOURCE: no start and gauges go up and down

I would be checking all of your fuses inside the cab and in the engine bay, check the water in the battery, give the terminals a clean with a steel brush and get your alternator check as it may not be charging the battery good.

SOURCE: Electrical issues. Voltage gauge drops then goes to normal

I Found that the outboard PCM cover screw was shorting out the circuit board.

Short story long: I have a 97 Grand Cherokee 4.0L, 138,000 miles. Several weeks ago, I started to have stalling issues. Hot or cold, dry or wet, first drive of the day or last, it didnt matter. The engine would cut out. It felt like it lost all electricals.
At the time it was showing an ASD relay code and primary coil/ secondary ignition code. Swapped the ASD and A/C relays and replaced the coil and iac valve. Same problem. I didnt have time to look at it, so I had the dealer go through it. After 2 days and $200, they called and said it was the ASD relay, and that they put in a new one, and its all good. Um, ok, maybe I missed something. Im a trusting soul, but lets see if this fixes it. The next day the problem was back. I went back to the dealer and they basically said, We dont know what it could be, good luck with that. Now my wife knows why I dont go to the dealer. By the way, the old relay tested good.
My turn. I cleaned connectors, ohmed out wires and sensors, checked for power and grounds. Everything checked good. By now, its showing ASD, crank sensor, and primary ignition codes. Then, with my wife trying to start it, I wiggled the connectors on the PCM. Every time I wiggled the gray C3 connector just right it would run. When I let go, it would die. So I took the connectors apart and tightened up the crimps (I dont recommend doing this without the proper extractors and crimper). Threw it back together and BAM! Same problem. Well, time to bite the bullet and check for bad solder joints on the PCM board. I took the cover off of the PCM and realized that looking through the potting compound is like looking through Guinness Stout. But, I put it back in and hooked it up. It started stronger than ever, and didnt even think about stalling. Yes! I figured that I finally got the connectors sorted out, so I left it over night to cool down. Got up the next morning and it started right up and wouldnt stall even when wiggling the connectors. So I put the cover back on, put the PCM back in, hooked up the connectors, and BAM! It wouldnt start! That was the point when my wife asked, Hows it going? And I, being the methodical aircraft mechanic that I am, said, what the ----? Thats when my wife turned around and went back into the house. While smoking a pack of cigarettes, I thought, Gee, it runs with the cover off, but not with it on. DUH, wonder what it could be? So I backed out the two screws that hold the cover on and BAM! It started right up. Then, while it was running, I tightened the outboard screw and sure enough, it died. I cut the screws (1/4 long, factory screws are 1/2 long Torx head) with a pair of wire cutters , and shes been running great ever since

SOURCE: Oil pressure gauge reads 0, until you accellarate.

This really sounds like your oil pressure sending unit. You don't say what engine you have but check your oil make sure its full and clear you don't want to loose the engine over this and you should n't but check it.The unit threads into the block some are in the back behind the distubtor some are low on the side in the front but they all thread into the block somewere And usely you need a speical scocket to remove it but there pretty standard one socket fits all of them Check at hte auto parts store when they pull it up on the computer ask to look at the screen and it will show you exactly where yours is good luck