AZRick Posted September 18, 2015 Share Posted September 18, 2015 Jeeps, it's always something :doh: Recently I installed a 241 transfer case out of a 2004 TJ Rubicon into the MJ. The speedo connector being different than the 1991 version of the 231, I didn't bother with it. I have an old/small garmin just perfect for use as a speedometer. Now I am getting a check engine light while driving, it goes out after a restart but always comes back after a short driving distance. Can't remember offhand but seems like it is still triggering the "shift" light. Can the computer be throwing the light because it's not seeing a speedo imput (the 91 speedo is electric)?????? Link to comment Share on other sites More sharing options...
Eagle Posted September 18, 2015 Share Posted September 18, 2015 What code is it throwing? Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 18, 2015 Share Posted September 18, 2015 It's a code 15., Speed sensor or circuit, No signal detected from speed sensor. Check circuit and sensor. No input because it's not connected. It a simple reed switch that makes and breaks as the driveshaft turns and sends the pulsed signal to the ECU. The 91s use a 2-wire sensor and the newer models (mid-92 and up) use a 3-wire. Do you still have the old 231 case? You could pull the speed sensor and housing from that and swap it over. I know it's possible with the 242 t-case. If you had an auto you would really be feeling it missing shifts right now. Mileage will be affected also...... Link to comment Share on other sites More sharing options...
AZRick Posted September 29, 2015 Author Share Posted September 29, 2015 Thanks for the response, it's what I was afraid of. The 91s are a bastard year, there is still a gear drive between the reed switch and the 231 tcase output shaft. I had to change gears to get the speed right after installing the 4.56 gears. In the later models there is no gear drive, just a reed switch, no way for them to physically interchange. I'm going to have to figure out the wiring... I have a year before emissions are due. :yes: Link to comment Share on other sites More sharing options...
Crash Posted September 30, 2015 Share Posted September 30, 2015 IIRC< dakota digital makes an apparatus to solve your issue. Not cheap, but it should work. Or maybe find a way to wire in your current sensor to your speedo circuit. Link to comment Share on other sites More sharing options...
AZRick Posted October 3, 2015 Author Share Posted October 3, 2015 IIRC< dakota digital makes an apparatus to solve your issue. Not cheap, but it should work. Or maybe find a way to wire in your current sensor to your speedo circuit. Digging around more, the 231 uses a reed switch, the 241 is "VSS" so yea the dakota digital looks like the answer. Link to comment Share on other sites More sharing options...
AZRick Posted October 15, 2015 Author Share Posted October 15, 2015 IIRC< dakota digital makes an apparatus to solve your issue. Not cheap, but it should work. Or maybe find a way to wire in your current sensor to your speedo circuit. Digging around more, the 231 uses a reed switch, the 241 is "VSS" so yea the dakota digital looks like the answer. The 91 is a weird one off screwball. The reed switch setup was only used in 91s and early 92s. It is a 2 wire setup, the ECU supplies 5V to the reed switch, the "return" wire goes to sensor ground. The reed switch makes/breaks this circuit, which the ECU and Speedo in turn interpret as the speed the vehicle is moving. The 241OR has a hall effect sensor for speed, 3 wires, 5V + ground and a three notches in the output shaft of the transfer case results in a signal being delivered to the third wire which returns to the ECU and speedo. In other words its a 3 wire system with a ground plus out an back legs. The 91MJ is wired for a out only (power to the speedo is split off at the G7 splice). No amount of tweaking the signal post hall effect is going to have any effect on the speedo/ECU as they are looking at the constant 5V on the up side of the sensor. I think I can make the speedo work but not supply any info back to the ECU. Of course that will result in a check engine light (its the map sensor telling the ECU the engine is under a load without a speed input) and stalling at stop lights. I am thinking about making a disc to press onto the transfer case output yoke (there is room), three magnets attached to the disc and a reed switch. I should have in signal for the ECU and speedo. Thoughts? Ideas? Link to comment Share on other sites More sharing options...
Eagle Posted October 15, 2015 Share Posted October 15, 2015 You can't just move your old speedo quill to the "new" transfer case? Link to comment Share on other sites More sharing options...
AZRick Posted October 15, 2015 Author Share Posted October 15, 2015 You can't just move your old speedo quill to the "new" transfer case? The physical differences are insurmountable. The 231 is gear driven, the 241OR is electronic i.e. no moving parts. Link to comment Share on other sites More sharing options...
AZRick Posted October 15, 2015 Author Share Posted October 15, 2015 Anyone have a 92, 93, 94 or 95 xj wiring diagram? I need the pin in/outs for the ECU, maybe I can use a later version ECU and rewire the MJ. Link to comment Share on other sites More sharing options...
87MJTIM Posted October 15, 2015 Share Posted October 15, 2015 Go to Morris Jeep 4x4. in the bottom left of the main screen, there is "Jeep Community: Jeep Knowledge Base" Go to the Repair manual section. Search for the model and yr. I got the whole 93 XJ/YJ FSM Link to comment Share on other sites More sharing options...
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