Just got though changing out my engine,(3.0) adding Downey headers and doing other mechanial repairs to the trans and transfer A340H, nothing internal. Both the speedometer and the 4X4 on light in the dash stopped working. Everything else works fine and 4WD is engaging. Trying to figure out what these two have in common that might be causing this problem. The light bulb is good. OD, ECT and AT Temp lights work!! Anybody got an idea?? These factory electrical diagrams leave alot to be desired!! Any suggestions will be appreciated!!

Two simple things to check first: Is the VSS and cable plugged into the transfer case and is the 4WD switch connected to it's cable again on the passenger side of the transfer case?

4Crawler I check them all and they were pluged in but will check again since I did move some wires around to clear the headers and exhaust!! Thanks for the get back!!

Check the connections. I just put my truck back together and the speedo wasn't working. The connector was on just not pushed all the way in.

I'm reading codes 14, 21 & 42. The 21 is explainable since the o2 isn't hooked up yet. The 14 IGF signal from igniter is not input to ECM for 6 consecutive ignitions & 42 SPD signal is not input to the ECM for at least 8 seconds during high load driving with engine speed between 2,750 rpm and 4,000 rpm are the ones that I can't explain!! Help needed can not make heads or tails from this FSM. Need something a shadetree mechanic can understand. As you can tell these computers aren't my cup of tea!! Open for suggestions that I can understand. All connection are in place as best I can see. Will get under there and hand check each one for good clean connection!! Thank you!!

I would guess the SPD signal is the same signal that the VSS feeds to the speedometer. Check out that sensor and the connector and wiring between the tranny and the ECU. And hook up the O2 sensor, that should fix the fix code. Clear the codes once those are done and try it again.

i have had the similar prob, after i R&R'd my clutch the 4wd indicator light wont turn OFF. i have got under thier and connected and unconnected and brushed and electro greased to no avail. i was curius cause all i did was take it apart and put it back together, that is the only light that is on and i haven't been able to try a scanner yet.

I've also had that same problem with the light not going out but it was as simple ajustment of the transfer linkage that turn it off when in 2WD but this one is being a PITA!!! I don't even know if you have linkage since yours is manual but if not check the transfer indicator switch, might be defective or hung up!! Good luck!!

Found the problem on codes 14 & 42. Terminal SP1 at ECM wasn't grounging. Does anybody know where the transfer on indicator switch is located on the 94, 3.0, 4X4, Auto, A340H trans?
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try this link. http://personal.utulsa.edu/~nathan-buchanan/93fsm/autotrans/34electron.pdf page 2 has a diagram.