Advice Requested: Driving with TOD Check Light

Ok so here's the deal... I got back from a trip late last night and when I started the VX in the airport lot the TOD Check light immediately came on for the first time. My mechanic is going to jump the pins to read the code (couldn't find anything in the garage to do it myself) in about half an hour so I'll post that here when I found out.

But my question in the interim is this: Are there any codes that should preclude me from driving it about 2 1/2 hours away from home IF I can't get it fixed by the time I leave on Thursday night? I don't want to damage anything further, nor do I want some odd drivetrain behavior to occur while I'm doing 70 on the interstate.

Thoughts?

My TOD light still starts flashing after about 20 minutes of driving. It's never bothered me enough to check for codes. This has been going on for several years now with no adverse effect (of course for the last year I've been running locking hubs too so that helps).

The light is just telling you that you aren't getting any drive to the front. It won't be able to tell you that your transfer case is about to explode.

Ash, was it very cold when you started the VX? I ask because when we had a super cold snap here in Colorado my TOD check light came on one morning when I started the VX. I went into a slight panic, but had to get to work so I, gingerly, drove on. On my way to work the TOD check light started flashing which sent me into a greater panic, and when the lights on the front wheels of the TOD display started dancing around I just about had a heart attack. During all of this I didn't hear or feel the TOD actually kicking in so I kept soldiering on. I also started to notice that most of the dancing lights happened when I would hit a bump so I figured that it was just a loose connection somewhere. I was going to try and look around to find the problem, but as the temps have warmed up the flashing TOD check light hasn't come back so it's a little hard to diagnose and fix a problem that isn't there any more.:_confused

Hopefully your experience will be much the same.

Okay got the codes checked and it threw 13, 14, 24, and 31. :eek: We cleared the codes and only 13, 14, and 24 came back. Those three correspond to a ground and the front and rear speed sensors. 31 is for the electromagnetic coil (EMC) that's inside the transfer case so hopefully that was a fluke. I looked at the parts catalog and they show left and right specifications for both front and rear speed sensors. Which do I need? I'm not ordering from Isuzu (mucho $$$) so maybe trying Rock Auto later.

Mark it was pretty cold and had been for several days while it was parked. I never had any issue with TOD prior to the light flashing, and given that I had just driven it through ice/snow/salt the morning I flew out a wiring problem seems probable.

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Originally Posted by tom4bren

My TOD light still starts flashing after about 20 minutes of driving. It's never bothered me enough to check for codes. This has been going on for several years now with no adverse effect (of course for the last year I've been running locking hubs too so that helps).

The light is just telling you that you aren't getting any drive to the front. It won't be able to tell you that your transfer case is about to explode.

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It's good to hear that you can at least drive with it on, hopefully I can do the same until I figure out the fix. I've done a lot of reading in the repair manual and it seems like the TOD ECU just shuts down 4H completely and only powers the rear wheels if it detects any kind of problem. 4L still works fine - is that because it's a manual engagement vs. a computer controlled engagement?

Is there a real chance that a sensor/electrical problem with the TOD system could cause the transfer case to explode (or at least to break and not function)? Or is TOD smart enough to not let that happen?

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Originally Posted by vt_maverick

It's good to hear that you can at least drive with it on, hopefully I can do the same until I figure out the fix. I've done a lot of reading in the repair manual and it seems like the TOD ECU just shuts down 4H completely and only powers the rear wheels if it detects any kind of problem. 4L still works fine - is that because it's a manual engagement vs. a computer controlled engagement?

Yes

Is there a real chance that a sensor/electrical problem with the TOD system could cause the transfer case to explode (or at least to break and not function)? Or is TOD smart enough to not let that happen?

No. TOD is the the computer/electronic clutch system in the TOD. The flashing light doesn't tell you anything about the mechanical aspects of the trasnfer case. If there's an electrical issue with TOD it will not cause a mechanical failure.

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:smack:

As a side note for anyone considering going 2WD in a future driveline conversion, I can definitely feel the difference without TOD and it's not for the better. Maybe if I still lived near the beach where it's nice and flat it wouldn't be a big deal, but when the road you live on is 20 miles of non-stop S-curves, switchbacks, uphill climbs, and sharp downhill descents that extra grip is really noticeable, especially in the twisties.

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Originally Posted by vt_maverick

As a side note for anyone considering going 2WD in a future driveline conversion, I can definitely feel the difference without TOD and it's not for the better. Maybe if I still lived near the beach where it's nice and flat it wouldn't be a big deal, but when the road you live on is 20 miles of non-stop S-curves, switchbacks, uphill climbs, and sharp downhill descents that extra grip is really noticeable, especially in the twisties.

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on my wife's trooper when TOD was flashing - front wheel drive was engaged and it feels like at 50\50 power distribution. was very bindy on sharp turns. on slow mo - sharp turn - truck did not cooperate at all - wants to go straight - not in turn.

Were the front wheel lights lit when that was happening? My front wheel lights in the TOD panel are completely off now unless I'm in 4L.

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Originally Posted by Dmitrikr

on my wife's trooper when TOD was flashing - front wheel drive was engaged and it feels like at 50\50 power distribution. was very bindy on sharp turns. on slow mo - sharp turn - truck did not cooperate at all - wants to go straight - not in turn.

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I can see it failing either way. If you are getting drive to the front when the TOD is malfunctioning, you should disable it. Either find the right fuse to pull or disconnect the TOD computer. You should never drive a 4WD on dry pavement with the trasfer case engaged (even by an electric clutch).

I'll cut the wheel hard to be sure...

I'm sure you would've noticed by now.

You're right Tom, I took the time to do a few slow donuts and no problems.

Yah, in my old '79 Dodge P'up with full time 4WD, I got significant bounce in the front in tight turns.

tom4bren

melted wiring cause the problem on my wife's trooper - too close to exhaust - melted insulation cause short in sensors signal wiring.
Fixed, everything works now.

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Originally Posted by Dmitrikr

tom4bren

melted wiring cause the problem on my wife's trooper - too close to exhaust - melted insulation cause short in sensors signal wiring.
Fixed, everything works now.

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Thanks. No melted wires that I've found. I'm sure mine is a sensor malfunction but honestly, it's just never bothered me enough to run the diagnostics yet.

Hey Ashley I've got the computer out of m race truck ir you want to try that out.

Sounds good Greg, I'll see if I can swing by Wednesday evening or Friday afternoon. Thanks!

I had this happen. One of the two speed sensors shorted out. Only had 2WD, and it's a major pain in the snow. They've been replaced at great pain to my wallet, but now I'm 4WD all the time. Mechanic says the TOD ECU was damaged.

Well thanks to Buffy for lending me the ENTIRE TOD system from his race truck (transfer case with speed sensors and electromagnetic coil, computer) to help troubleshoot. I thought wiring or computer since so many codes were thrown, but replacing just the speed sensors seems to have cleared up the problem.

Now back to my regularly scheduled non-fishtailing when hanging the 90 degree uphill left onto my street (ridiculous how fast you can go with TOD). :D