I also recently had some issues (unrelated to the SC install) with the speed sensors on the TOD unit. On 8/26 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 suspected that the front drive was disabled and it was causing load on the CV joints and that's the sound I kept hearing. The VX otherwise seemed to be unaffected, only noisy in the front, flashing TOD warning light and crappy handling - which would make sense since the front wasn't powered.
When I stopped and turn off the ignition, the flashing light went away, only to return when the VX was back up to speed. I looked in the VX Shop Manuals but they rely on pulling a code through the Isuzu proprietary 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 didn'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 thought the possibilities were 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 crawled under her and tugged on these to make sure the connection was good.
- Problem with the TOD ECU - 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 have been something 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 is that the ECU could be storing some error condition that isn't clearing - I did a full battery disconnect 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). Unfortunately the flashing light returned.
After exhausting the possibilities, time to take it to the dealer. 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 (that's Pugmire in Marietta for you Jawjan's). After leaving it there for a day they called me to say the TOD speed sensors were shot - they want $1100 to replace both speed sensors (parts are over to $300 each plus 4 hours labor). Sounded like a load of BS to me - lot to pay for labor that, once I reviewed the cd manual, looked easy (1 bolt on each sensor) - so far I was only out the $95 for the diagnostic.
Since no one stocks the sensors and I really shouldn't be driving the VX while it's mucked up, it was better logistically to buy and replace them both. $612 for the pair from Merlin and they were supposed to be at my house on Friday. In the meanwhile I rented 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 had to have the car as I was heading up to TN to visit the family that weekend (Labor Day). Even with the rental it cost 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 above and below the TOD unit and it didn't look like there's much in the way to replacing them. I was just hoping that that's the only thing wrong and it wasn't symptomatic of another problem. That was my fatal error - thinking it would be easy.
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 buried 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 gets 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 go 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 wouldn'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 figured 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 flashing 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.