Flashing TOD Light - think I broke my truck

I think I broke my VX!

Yesterday I was travelling up to Athens GA pulling an unloaded trailer when the TOD warning light starting flashing. I then noticed that the front was making noises during turns. I suspect that the front drive is disabled and it's causing loads on the CV joints and that's the sound I'm hearing. The VX otherwise seems to be unaffected, only noisy in the front, flashing TOD warning light and crappy handling - which would make sense since the front isn't powered.

When I stop and turn off the ignition, the flashing light goes away, only to return when the VX is up to speed. I looked in the VX Shop Manuals but they rely on pulling a code through the Isuzu propriatary OBD-II Scangauge which I don't have - my generic scanner didn't show any codes. I went ahead and drained/refilled the TOD case and made sure there was gear-oil in the front differential (recently changed that). I don't see any obvious damage to boots, ect in the front end and no smoking or grinding (other than when making tight turns, which I would expect with the FWD off).

So I'm thinking the possibilities are as follows:

• Problem with the TOD unit - I felt around to make sure the connectors were engaged and the speed sensors and TOD links all looked good - I may crawl under her today and pull these apart to clean them and make sure the connections are good.

• Problem with the TOD ECU - haven't looked at it yet, but since the TOD lights seem to be working correctly, it would have to be a very specific hardware issue within it's circuitry to have gone bad - not very likely.

• Issue with some front driveline component - could be something is fubar in the front-end that's not obvious and it's causing the front driveline to pass back some error condition - I'm thinking that this could be very probable and would be the worse case scenario.

The other possibility that Joe Black pointed out while on the phone yesterday is that the ECU could be storing some error condition that isn't clearing - I'm doing a full battery disconnect today to see if that is so and if it might clear it up (this could be linked to the extra drag from the trailer - you're really not supposed to pull something at 85 MPH I guess, and coming to a stop might have put some stress on the TOD - just a possibility).

Has anyone else experienced anything similar and if so, what did you do? The only Isuzu service center I know about is in BFE from my house and it would be a bear to get to in traffic tomorrow (plus I'm not sure if they actually do any work other than regular maintenance anymore - that's Pugmire in Marietta for you Jawjan's). Comments are welcome and I'll update once the battery disconnect happens.

-- John

Battery reset had no effect. I'm taking her into the dealer tomorrow - sigh. Maybe I'll get lucky and it'll be covered by the 120k drivetrain warranty (not counting on that though).

-- John

Grab hold of your axle shafts and give them a push and tug to see if there is any play. Possible that you blew a CV which is causing one side to spin when engaged throwing a code! Just a thought!?!?

Well - after waiting all day for the dealer diagnostic, they want $1100 to replace both speed sensors (parts are close to $300 each plus 4 hours labor). Anyone else experienced that? Sounds like a load of BS to me - I'm going to pick her up and do some more research. So far I'm only out the $85 for the diagnostic.

-- John

I think it highly unlikely that two sensors would fail simultaneously. I wonder if they come into the harness near each other or share some other common loom space, or perhaps there's an issue with the hardware or code that reads their output.

If you want to swap parts off my Ebony over at Schellenberg's feel free, that may help narrow the cause and put you back on the road.

The deal is that when you troubleshoot it's not specific to whether it's the front "A" or back "B" sensor. Since no one stocks them and I really shouldn't be driving the VX while it's mucked up, it's better logistically to buy and replace them both. $612 for the pair from Merlin and they should be here Friday. In the meanwhile I got a little econobox to drive around from Enterprise for $235 for the week (figuring I'll be saving on at least 2 fill-ups it's technically only costing me about a hunert bucks to drive around). I've got to have the car as I'm heading up to TN to visit the family this weekend. Even with the rental it's costing me less than the dealer's $361 each for the sensors plus labor (and I would need the rental anyway).

FYI the sensors are mounted before and after the TOD unit and it doesn't look like there's much in the way to replacing them. I just hope that that's the only thing wrong and it's not symptomatic of another problem. Thanks for the offer on the Ebony - I didn't even think about that - too late now I guess.

Another FYI - I asked about availability on body panels and cladding and his computer was showing a fairly deep inventory (asked about the rear bumper cover as I banged mine up dragging a ladder on my trailer up to John's) - it's showing 29 available which is a far cry from last year when all the parts were getter rare as hen's teeth. Guess they shipped over some to cover what was needed with existing ownership. He mentioned for a while there was a 4-6 month lead time of body panels last year but that seems to be fixed.

-- John

I just took another look at the workshop disk - seems Joe is right and there is something fishy about both sensors being fubar - I'm taking a closer look when I get home this evening. Either the dealer is lying and I only need one (and they were too lazy to isolate which one is bad), or there's something going on with the harness that feeds the two. If the TOD ECU was bad it would show a different trouble code - but who knows what the dealer did to determine what was wrong. I took a hit from a piece of tire on the interstate last week - struck the passenger side front of the VX - no damage but I did notice the cladding was pushed in a bit - it could be pinching part of the harness that loops around the front of the VX - I'll loosen things up a bit when I get home this evening and see if it makes a diff (was going to do that anyway).

-- John

Thought I would follow up - peeled off the whole front of the VX to look for shorts in the harness - there weren't any so got busy looking at the wiring to the sensors - got the sensors during the week (supposed to be here 2 Fridays ago but they messed up and sent them to my old work address). Dismantling the existing harness was quite a PITA - there are plastic tabs that a bolt runs through into the TOD unit - each sensor has a round plug with a blue o-ring that's quite difficult to remove - have to gently pry all around until it loosens - I ended up breaking one tab from my existing bottom sensor (top came out first with no issue). You also need to disengage a tranny sensor that's also part of the harness. Once the harness is loosened up, you have to disengage the main connector on top of the unit - this was quite difficult as you can hardly thread one arm up there to grab it and the connector has to be mashed down for it to release - quite a bit of frustration there.

The connector can then be slid down the passenger side of the TOD by loosening the bolt holding the gas lines to the top of the case (you can then lift the lines and shimmy the connector under them). Once apart, all plastic wire casing has to be removed and the two sensors have to be unpinned from the connector (note that there are two wires who's ends are burried in the tranny that are still attached to the connector, so you're basically laying under the truck the whole time). I unpinned by removing the back and sliding a small screwdriver into the pin slots while wiggling the wire from the back.

The two new sensors are attached in a reverse of the above - lubing the o-ring with silicon helps but it's still a PITA getting them back in. Pinning into the connector isn't as bad as depinning. Once it's back together, electrical tape pulls the casing back on, making sure to reinstall the two wires you had to pull out for slack (the ones mentioned above that terminate in the tranny). Getting the main connector back together wasn't easy. Once you get the "click" you can bolt the connector back to the top of the case, bolt the gas lines back, reconnect the sensors and the 3rd sensor on the tranny (this one get's a zip tie too to help hold the wire out of the way). When it was back together I reconnected the battery (left out that it needs to be disabled while you work on this, as with any electrical system), got in and started her up. Started on the first try.

Drove her down the road and noticed a new, high pitched whine - this lasted until I goe back to the house and backed in. Next startup and the whine wasn't there - all this so far was about 5 hours dismantling last weekend and about 4 hours putting her back together on Saturday. This morning I got in her and once again noticed the whine, but much fainter - driving a few miles the whine went away completely - I'm not sure what it was and hope it's not something that will come back to haunt me later.

Last week, when I realized the parts woudn't make it I had an offer from Joe Black to use the sensors off his ebony up at John Schellenberg's - he was nice enough to remove the piece of harness from Joe's and drop it off last Sunday morning (took him an hour to do this - dunno why it took me 5 to do the same thing! - difference in skill level I guess). After spending so much time fumbling with removing mine I didn't have it in me to finish (it was getting dark) so I figued I would just wait for the parts. Now I still have to put Joe's back in his ebony, but that can wait until next weekend.

Good news is that the flasing TOD light has gone away and she's driving great - guess that's what is most important. Note that I used the CD manual as a reference and it looked easy from that perspective - but this was anything but easy to do. If I had known it would be this hard I would have just paid the money and had the dealer's service group do it. I'll think twice next time.

-- John