Hello.......

I have a 93 Pickup 4x4 with 4 cylinder. I have code 21. Engine light comes and goes. But the code is not my problem. Yesterday for the first time I was backing up then went forward and turned very sharp and my engine light light lit up and the truck died. If I remove the EFI fuse and put it back in the truck starts. It happened again today several times. Same thing, if I remove the EFI fuse and put it back in the truck will start. I have searched the forum for this issue but could not find anything. Not sure if the 21 code is related to "NO" check engine light when I try to start. Maybe bad ECU? Truck runs excellent. 260,000 miles on the truck. 52,000 miles on rebuilt engine. I just picked up this truck so I don't know what all has been done.

 

I just remembered when it happens I hear a pop. Maybe the trucks EFI's relay or Fuel Pump Relay is going out? Could a code 21 be caused from either the EFI or Fuel Pump Relay going bad?

 

If your reading the blinks correct code 21 is the oxygen sensor

Time to do some trouble shooting and figure out just what is wrong.

Could your EFI fuse or relay be loose in the socket??

 

Wyoming thanks for the reply. Yes code is 21. I have checked all relays/fuses and everything seems good. I must have a electrical short or other issue that is tripping the EFI or Fuel Pump relay at intermittent times. The truck runs excellent. I will double check all electrical connections today.

 

Could be you have wires being pinched as things flex.

It also could be a loose ground causing these gremlins

 

Follow the O2 sensor wiring and look for breaks in the insolation.

 

Thanks Punchy. I will check that out tomorrow.

 

I wanted to update this topic. I purchased a new EFI relay today. Put the relay in and the truck seemed to be turning off more frequent. I got the truck started again and pushed on the fuse box and the truck turned off. So when I got home I unbolted the fuse box and removed the bottom to find that the alternator fuse block had been burned pretty bad. Wire was good. But the alternator fuse block had at one time got really hot. I picked up another one at the wrecking yard today. Not sure if that is my problem until I drive the truck. But I am assuming since the Alternator 80 amp fuse is directly next to the EFI fuse which was getting hot and going out it was related in some way. I also noticed that my volt meter in the dash shows a little lower now when the truck is running with the new alternator fuse-block.