Gee, this is kinda embarrassing to admit but I don't have the faintest idea of how to use an engine scanner. I am an old boy who used to be able to do most anything on 1950's - 1960's - 1970's vehicles but the newer ones confuse me.

I looked up engine scanners on Amazon and I found one that is SUPPOSED to work on a 1996 T4R. AUTEL MAXISCAN MS 309 UNIVERSAL OB2

If I read the product info correctly, it works without the engine running ????
All that is required is a good car battery so the scanner gets it's power from there ????

Can a 1st time user do-it-yourself guy figure it out or does it take a mechanic ???

Go to the store and buy a $20 OBD2. Nearly anybody will have one, and most places will scan your car for free.
Turn the car to acc, plug it in and wait.
There should be a button with a picture of an eraser (or maybe labeled "erase" or "clear") which will remove them from your ECU.

Good description, long distance troubleshooting.
Simple place to start rule out engine seizure, try turning crankshaft at crank pulley bolt clockwise rotation.
For a quick check plugs in, easier to rotate plugs out. go from there.

I am on my way to the local Auto Zone store here in Mexico. If they have an OB2 with English instructions, I'll buy it.

Question: will it tell me ALL of the possible codes it has thrown recently ? And how do I know which code is the one that tells me why the check engine light came on ???

That's how CEL's work - if it is on, it means a code is being thrown (long story short.) Any code it gives you, investigate what it is. The scanner may or may not give you a brief description, or it may just show you the code and leave you to google it. Sometimes you have to use your imagination and knowledge of how a vehicle works, depending on what code it is. For example if you got P0171, it could be O2 sensors (faulty or failed), MAF (dirty, faulty or failed), vacuum leak, etc. so it helps to start with the easiest fix and work your way up, maybe using the OBD to check if the afflicted parts are getting proper voltage. But (for example) if you have P0325, it only means one thing, that particular knock sensor is shot - no if, ands, or buts about it
It sounds much more complicated than what it is, and some people can find code scanning unnecessarily daunting, so I always recommend searching on google as a first step; usually something like "4Runner [code]" or "[year] 4Runner [code]." A while back I was told to google things as a first step because "chances are there's been a ton people in your position, far dumber and less capable than you," and it's very rarely failed me
OBDs will show you all recent codes that have been logged in your ECU. Sometimes your vehicle will log codes without tripping the CEL (called "pending codes"), but for your sake that's not really relevant here. Whatever the scanner tells you, post it here and search it up

Thank you Devbot. That helps a great deal. When I buy a scanner, I'll talk about it some more. One rather queer thing, I just tested the battery. It had only 11.3 volts. I say odd because I replaced the alternator last month and it was putting out 13.2 volts at idle
I can't help but wonder if the low voltage was the cause of the engine shutting off while I was doing the engine flush . Certainly it is the cause of the engine not even trying to restart right now.
IF I had a low voltage do you think that that MIGHT have caused the check engine light to come on ? Maybe a sensor was not getting enough voltage to work ????
Right now the battery is being trickle charged overnight.

Yes, yes and yes.

Bad battery if alternator is putting out over 13v.

Remember to finish the engine gunk treatment, haha....

good heavens. the battery is only 2 months old. WOW ! It is certainly possible that I have misremembered about the voltage AT IDLE. Maybe I am remembering the voltage when I Rev'd up the engine, just after I changed the alternator a month ago. At age 74 I do forget stuff.

Yes, if the truck starts tomorrow after an overnight trickle charge, I'll keep it running for 5 minutes to finish the engine flush. Afterward I plan on changing oil with 5 W-30, 1 quart of Rislone engine treatment and a new oil filter. run that for a month or so, and repeat with another oil change.

UPDATE: The mystery deepens.

After having the battery recharged to a full 12.6 volts, the truck started right up. (so, it was not seized up). As I had only done 3 minutes of the 5 minutes required to do the engine flush, I ran the engine for 2 more minutes. Just as I was about to turn the engine off, it suddenly stopped dead and would not restart.
The battery had been disconnected for 3 days during this week-end holiday. I wonder if during that time the computer somehow rebooted itself ? ???Maybe I'll disconnect the battery again and let it sit for a few days to see if the engine will restart. Hell, I'm about as confused as possible as to what is happening.

In any event, I drained the crank case and changed the oil to 5W-30 with one quart of Rislone oil treatment, and a new oil filter.
PS: after the engine flush, the oil was very black, even though it had only 50 miles on it. So, lots of sludge.

If the engine restarted after you charged your battery, and then died again while running, it sounds like the alternator isn’t charging the battery. The ecu doesn’t really reset or anything after disconnecting the battery so I doubt that’s it

I also considered the alternator,(which is new) but AFTER the engine shut off I checked the battery voltage, It was STILL reading 12.5 volts. Hmmm.

I think you have a bad connection somewhere.

A failing crank sensor will stop an engine but it will still turn over. If yours doesn’t turn over you need to start looking at the ignition switch etc.

Do you have dash lights when the engine dies?


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Yes, I still have dash lights when the engine shuts off.
I just double checked the battery voltage, it is still reading 12.6 volts.
Even if there was no alternator in the truck it should still start and run for awhile.
Just to run a test, I disconnected the battery and I'll try to start it again tomorrow.
I was planning on removing the throttle body, and give it a good cleaning with CRC throttle body cleaner. I could be wrong but I think I read somewhere that if the throttle body is dirty it can cause the engine to shut off when idling.

It turns over and doesn’t start after it shuts off?


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This morning I put the recharged battery back in and the truck started right up. But, after running for 2 minutes it shut off without even a shudder.
I tried to restart it but it would not start or even crank over. . That is EXACTLY the same thing that happened last week.
PS: the battery is currently registering 12.6 volts.
I'm no mechanic but it seems likely that the computer is sending bad info ????