95 Trooper Check Trans Light

Looking for direction... 95 trooper 111,000 My "Check Trans Light" came on after driving for about 75mins. I got to my destination, shut the car off, when I started up an hour later, no
light. Was able to drive 200+ miles since. Today it came on again in the morning, I stopped for coffee,(shut the car off). When I restarted, the light stayed off and I drove another 40 miles with out incident. Any ideas/guidance? Also any advise on attempting to read the fault codes? thanks..
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When I had a '93 Trooper, it started to happen to me after my alternator went of the flitz (must have spiked the electrical system)...shortly after my starter went (what a coincidence).
Back to your problem though... It seems as though mine did it when it was damp and cold out (usually on startup)...It had nothing to do with the transmission, (at least on mine) and everything to do with an electrical problem (when damp out, after starting the vehicle, it seemed to sputter a bit (thus if you started driving, the trasmission computer thinks you are having a problem with the transmission and puts it into "limp" mode- straight 3rd gear).
If you have a repair manual, it may have something in there on how to read the codes (without a code reader) I think I had to short 2 pins together on the plug on the Drivers side under the dash, then the light would flash the code back to me- came back as some transmission solenoid. I didn't think that was the case because it would only happen on a rough idle after starting.
I read somewhere that many electrical problems on the Troopers happed from oil "pooling" in the spark plug wells- IMO due to a manufacuring defect that ISUZU is not taking care of, but that's another issue. Try removing all of your sparkplugs and see if any are coated in oil (3 out of 6 of mine actually were coated on the outside of the plug- where the boot plugs on to them) Isuzu does sell a new spark plug wire set which is suppose to stop the "pooling" of oil by sealing the spark plug well better with a revised boot- I think the set was $60 or so from the dealer, but make sure you get them from the dealer, as aftermarket may not be revised to current Isuzu specs. also replace your plugs then and be sure to coat the wires with dielectric grease (lots) otherwise you will not be able to get the wires out without ripping them.
Hope this helps.
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SteveH wrote:

Often when this happens the car will act like it went into neutral. Quickly turning the engine on and off will likely fix the problem (right then). The following was posted by a service manager (accidentally snipped his name) some time back. The question comes up from time to time.

We did a complete service on ours (flush and change) and replaced the battery and the problem went away. In our case the battery was bought in an emergency while on vacation and was way to small which exacerbated the alternator problem (we suspect). From what I remember some alternators have bad regulators and that causes a spike in voltage which causes the computer to get involved. Try the on/off idea and if it works perhaps you can find someone to check the alternator to see if it is spiking. Hope this helps.
Frank
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thanks for the info. I tried the on/off and it worked. So it definately seems as if its a electrical problem. It seems to add up since I have left my lights on twice in the last 1.5 months and completely drained my battery and had to get a jump. Quick question, do you think I could get away with just a new battery? Also, I also seem to be getting a lot more background interference on my radio when I accelerate. Do you think they are related? thanks again...
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SteveH wrote:

Strictly guesswork. Mine was kind of accidental. I put the small battery in my Chevy S-10 (it went dead) and replaced the one in the Isuzu with a new one. Unless the battery is definitely bad I would lean toward the regulator. If I remember one poster correctly you need a guy whose sharp on this stuff to catch the spiking. No idea about the interference but again, a sharp guy with the electronics would be the ticket.
Frank
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on second thought, you might be better off with a new alternator, as when I did mine (93 trooper at the time) I replaced it again about 6 months later- charging circuit went hay-wire again. I don't know if the remanned ones have new regualtors installed, or if they just use the old ones if they test ok (sure test ok today...tommorrow- who knows?) Anyway, unless they know for a fact that the regulator had been changed as well (in a rebuilt alternator) I would go with a brand new one.
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If you are going to take the alternator off and have it checked at a shop, your best bet then, would be to replace the whole darn thing as the regulator is built into the alternator before other quirky problems start. Also by your battery being dead 2 x and your alternator working extra hard to recharge, it's possible you may have a bad cell in the battery, and now the alternator may have a problem with one of the diodes in the rectifier within the alternator... bottom line, I would start with a new alternator and battery. The interference on the radio may be caused by a bad charging circuit (should be filtered by the battery though) try the replacement of both and see if it goes away. If you can do the work yourself, it should be under $200 for a rebuilt alternator and battery.
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I have a 93 Trooper and had sort of the same problem. It would go into limp mode until I turned it off and then on again. This would cure it for a while. I put two or three batteries in it and this worked for a while also. Finally took it to someone who new what the heck he was doing(NOT THE ISUZU DEALER).He drove it home for about a week with all his meters hooked up to it. Turns out it was the regulater on the alternator that was going bad and sending a surge to the computer!It was spiking up to 18 volts and the computer was seeing this and went into "limp". Since having it replaced last year have not had one bit of problem......................knock on wood................Jim
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well I replaced the alternator and the check trans still came on. One thing I did lock in on, is that it only happens after the trans shifts up from 3 to 4th gear. that has been consistent.
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Well I did replace the alternator but no luck. Trans light is still coming on. I did observe another pattern which was that the light only comes on after the trans upshifts from 3 to 4 gear. Any other idea...I'm about to give it in and take it to a tranny shop...
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The cause of my trans check light on my 1994 turned out to be a short in the wiring harness. Unfortunately that discovery didn't come until after the problem continued after the trans computer was replaced.

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