Hey Guys,

I'm new to the forum, i recently bought a 02 trooper 4x4 with the TOD system. Recently the transmission has been flashing the auto light on the TOD display without throwing a code (no check light). This issue occurs at about 35-40 mph when my foot is off the gas. You can hear the transmission clunk when it switches. The Auto button is not pushed, this happens when it is operating in 2wd. I thought it could possibly be a speed sensor. I replaced the one at the rear of the trans by the driveshaft (rear). The cruise control is now operational but still the auto flashes intermittently (usually after an hr of driving or so). Any ideas? I have it at a trans shop now, but they are saying it has no codes.

I was going to replace the front speed sensor as well, but cannot locate its location. What i ordered looks like the high low switch, but has the key (rod) of a speed sensor. I'd hate to blindly throw parts at it. I know it is supposed to have 2 speed sensors, 5 solenoids, a high low switch, a computer, and intricate vac lines but i need some advice on deciphering the cause of this.

 

I wanted to reply with updates incase someone comes across the same issue as myself. The trans shop has 3 different scan tools they use for finding codes. Unfortunately since there are no codes they can not acquire any information on why my vehicle engages auto. They did tell me that the left front wheel is being engaged whenever the auto light flickering occurs. They are sending the vehicle to another shop, one that has the GM tech II scan tool and an Isuzu scan tool. Hopefully this other shop will be able to pinpoint the issue.

 

Another update, figure it is best to post updates incase anyone comes across similar issues in the future. The culprit is believed to be the vacuum actuator. This little part sits towards the front axle under a small skid plate. Typically vacuum is stored here to engage the 4 wheel drive hubs, however it also sends a signal to the vacuum actuator motor which further sends signals to the speed sensors telling the transmission to engage the 4 wheel drive mode. I wish i knew a way to bypass this whole system and just drive the vehicle permanently in 2wd mode. The part is available from a warehouse in California. I'll post again if this part actually fixes my vehicle. I'm skeptical.

On another note, i ordered the front speed sensor a while back and couldn't find it's location. Whenever i get my vehicle returned from the shop i'll take a look around and see if i can't find its location. I'm assuming it should be towards the front of the transmission somewhere around where the front driveshaft meets, however i thought i looked pretty thoroughly last time to no avail.

 

Thanks for the updates. Issues like this can be very frustrating.

 

I got my trooper back from the shop, they replaced both front vac actuators. Although the actuators were bad this is not the cause of my problems. The TOD indicators no longer flash and they illuminate the front wheels and i can successfully engage the 4wd now. But my problem occurred once again as i was driving it yesterday. The center light on the TOD started flashing auto when my foot was off the gas going about 40mph. I think it could be one of two problems. I'm trying the cheaper route first. I ordered a new throttle positioning sensor. The throttle positioning sensor has many pins and one pin sends a signal to the PCM and further sends a signal to the front speed sensor. This TPS sensor is readily accessible and bolts onto the throttle body housing. I ordered the part for $50 off ebay. If this does not work i can only assume it is the front speed sensor (i mean what else could it be?). I have no clue how to access this front speed sensor given it sits on top of the trans itself. I guess i have to take apart the shifter column by the floorboard. Furthermore, i'm not sure what this sensor looks like or how difficult it is to replace it. Does anyone have any experience for the R&R front speed sensor? The sensors they advertise on ebay for this vehicle are the VSS (vehicle speed sensor) which sits by the rear yolk (i have already replaced this faulty part) the high/low switch (sits next to the VSS) and a front speed sensor (1 1/4 " three pin connector screw in style sensor).

 

Had similar issue. Front speed sensor was replaced solving the problem. Garage gave me option of used vs new as cost of new sensor alone was over $400. Couldn't get sensor alone used; had to purchase transfer case to get the sensor. Garage decided to replace it as a set and so far so good.

 

rear wheel sensor far left is the rear wheel sensor , the larger one is the vss speed sensor it has the chrome or metal ring , the far right is the front wheel sensor .im look at a part #d24436 and d54922 around $40.00 . check all vaccum line under front axle remove cover and you do have vaccum line in front of intake aswell right side of if you are facing engine

http://www.bing.com/images/search?q=...lectedIndex=52

 

I took it to a shop, they found several burnt wires that were resting on the exhaust. They spliced in new wires and zip tied them up to keep them away. That solved the issue.

 

Not sure if I should have posted somewhere else, but I'm having a similar problem (but different)? I also recently purchased a 2002 isuzu trooper and have been having some issues with 2WD. When I first start up the car for the first few miles I get a clunking sound that seems to be coming from the transfer case. It almost sounds/feels like the vehicle is trying to go in and out of 4WD. Typically after a few miles it would go away and I wouldn't be able to get it to do it again. The kicker is if I select 4WD auto, it never happens. Does this sound like a speed sensor / Vacuum actuator issue? I took it in to an auto shop and they can't figure it out. I did mention what was said in this forum but they said because it works in 4WD auto, it wouldn't be an issue with TOD. They basically said that they would have to start replacing stuff to figure it out and parts are hard to come by. Any suggestions would be appreciated.

 

They actually found several bad wires on mine that did in fact get burned by the exhaust. After repairing them it works just fine. It definitely pays to take it to a shop that specializes in isuzus, bmw, or other foreign cars. I at first took it to a trans shop because regular car shops were unfamiliar with the tod system. The trans shop couldn't figure it out but at least they suggested a place that could. If it sounds like it is engaging, a good first step would be to test for vacuum at the actuators. They are simple parts to rule out and doesn't require diagnostic computers. You have to hook them up to a vacuum gauge and make sure they are holding pressure. If they are good, take it to a shop that has the tech 2 gm diagnostic computer. Few shops still have them so you may have to call around. The tech 2 can tell you if the speed sensors on top of the trans are bad. They are very expensive and not easy to access. I wouldn't blindly throw parts at it because it can easily cost you more than the value of the vehicle.