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I have a 1996 jeep Grand Cherokee 4.0 2wd. ever since we bought the jeep with 78,000 miles on it the over drive button has never worked on it. it now has 221,000 on it, when you turn the jeep on the light comes on for a split second and goes away. when the car is running and u click the button it does nothing, so its stuck in overdrive pretty much… i changed the relay under the hood and did nothing. i was woindering if there was a way to test it by connecting wires behind the module or something. this has been bugging me for ever. why isnt my overdrive button clicking on. it lights up for one second when i turn the jeep on and then it shuts off, so when i click it, it doesnt light up or do anything. the rear wiper button and rear defroster button work and its on the same module.trans fluid is at normal level and looks ok. also i have changed several modules out to see if it was that… its not lol PLZZZ HELPPP :ohmy: :ohmy: :ohmy: :ohmy:
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How did you actually do the test? Was the switch connected or disconnected? Terminals jumped or open? It should be zero resistance across the wires if the switch is closed or terminals shorted, and infinite if the switch is open or the terminals disconnected/non-shorted. If you have zero resistance regardless of the switch position of if the connector is unplugged and unjumped, the wiring is shorted somewhere. If there is zero resistance, and then you remove the jumper, open the switch, or disconnect the connector at the switch, the resistance should go to infinite. Please re-read the test procedure I outlined, and make sure you did it twice (both switch open/closed, or both jumper in/out) to verify wiring. If you have any questions, please ask. Because the wiring from the switch goes straight to the PCM, if the wiring checks out good, then it is a PCM issue.
ok well the way i did it was. i disconnected the overdrive rear defroster module and there was 2 wire harness, one long one that connected to the lowwer end of it and another one that connected to the top end but was shorter, i just stuck the ohms meter into the long wire harness which had the 2 wires you were talking about and got zero Resistance. is tht good or bd?
Was the C harness on the PCM disconnected? Let me explain a little more about what we are trying to do here. We want to isolate the two wires, the brown/yellow and orange, to where they are not connected to anything on both ends, or just connected to the switch. At the PCM end wiring harness (C connector, black color), we want to place the ohmmeter on pins C6 (brown/yellow wire) and C13 (orange wire). This is because we are trying to determine if the wiring between the PCM C connector and the OD switch is good. What we should see, with the ohmmeter connected to the wires at the PCM end, zero resistance when the switch is closed (or switch wires disconnected and jumpered with a paperclip), and infinite resistance when the switch is open (or switch wires disconnected and not jumpered, just open ends). There are only three possible outcomes: Good=If the resistance changes between zero and infinite when the switch is operated or the paperclip jumper inserted and removed. Bad=If it is zero in all cases, there is a short in the wiring somewhere between the switch and PCM. Bad=Infinite in all cases, there is a broken wire (open circuit) between the switch and PCM. The result of the test is this: If this test shows good wiring, the problem is in the PCM. Otherwise, the problem is in the wiring. This assessment also assumes that the switch itself has already been tested with an ohmmeter and found to be good.
Get the jeep to operating temp (drive 10 miles or so) leaving the car on, pull the parking brake and go from P to R N D pausing briefly in each and returning back to N. Check the tip stick- look for correct level and fluid color, transmission fluid is generally a bright translucent redish pink, the darker red in color or if its brown you need to change it.
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