4x4 problems possible gem?
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Joined: Jul 2018
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4x4 problems possible gem?
Hi, I'm having trouble with the 4wd on my 98 f150. I read back on some old threads and found a series of test to try and diagnose the problem. I'll copy and paste below.
[So now you've got to rule things out. First things first, check fuse 17 under the hood and fuse 12 under the dash. Then I would use a volt meter to first check that there is power at pin 3 then measure the resistance between the two dark blue wires at the switch, pin 3 and pin 2. The three positions of the switch should read 3.9k, 1.1k and 360 ohms. If they aren't then you have a bad switch.
If the switch is good you need to make sure the GEM is outputting the ground signals to activate the relay that shifts the t-case motor. Orange/light blue is the wire for high and brown/white is the wire for low, they should be pin 16 and 17. Check those two wires for voltage when the switch is in those positions. You should check them both at both high and low just in case i'm wrong about which is high and low. If neither of them have voltage that doesn't mean it's bad. The wires should be nothing or power at rest and ground in high or low so take your meter and again set to ohms put one lead on a good ground and probe the wires with the other. In high and low you should read 0 ohms on the orange in high and brown in low. if the wires are going to ground the GEM is good and you need to move on to the relay.]
Everything checked out til i checked the wiring at the t case motor. Those wires did not ohm out at 0. Does that mean the gem is at fault? Ib also went a step further and checked the solenoids. The solenoids themselves are fine but when you turn the switch from 2h - 4h the voltage stays on the disengage solenoid. It will randomly work but if does happen to go in 4wd it don't want to come back out. I have to repeatedly turn the truck off and back on till it will finally receive the signal to disengage.
[So now you've got to rule things out. First things first, check fuse 17 under the hood and fuse 12 under the dash. Then I would use a volt meter to first check that there is power at pin 3 then measure the resistance between the two dark blue wires at the switch, pin 3 and pin 2. The three positions of the switch should read 3.9k, 1.1k and 360 ohms. If they aren't then you have a bad switch.
If the switch is good you need to make sure the GEM is outputting the ground signals to activate the relay that shifts the t-case motor. Orange/light blue is the wire for high and brown/white is the wire for low, they should be pin 16 and 17. Check those two wires for voltage when the switch is in those positions. You should check them both at both high and low just in case i'm wrong about which is high and low. If neither of them have voltage that doesn't mean it's bad. The wires should be nothing or power at rest and ground in high or low so take your meter and again set to ohms put one lead on a good ground and probe the wires with the other. In high and low you should read 0 ohms on the orange in high and brown in low. if the wires are going to ground the GEM is good and you need to move on to the relay.]
Everything checked out til i checked the wiring at the t case motor. Those wires did not ohm out at 0. Does that mean the gem is at fault? Ib also went a step further and checked the solenoids. The solenoids themselves are fine but when you turn the switch from 2h - 4h the voltage stays on the disengage solenoid. It will randomly work but if does happen to go in 4wd it don't want to come back out. I have to repeatedly turn the truck off and back on till it will finally receive the signal to disengage.
Thread Starter
Junior Member
Joined: Jul 2018
Posts: 9
Likes: 0
Hi, I'm having trouble with the 4wd on my 98 f150. I read back on some old threads and found a series of test to try and diagnose the problem. I'll copy and paste below.
[So now you've got to rule things out. First things first, check fuse 17 under the hood and fuse 12 under the dash. Then I would use a volt meter to first check that there is power at pin 3 then measure the resistance between the two dark blue wires at the switch, pin 3 and pin 2. The three positions of the switch should read 3.9k, 1.1k and 360 ohms. If they aren't then you have a bad switch.
If the switch is good you need to make sure the GEM is outputting the ground signals to activate the relay that shifts the t-case motor. Orange/light blue is the wire for high and brown/white is the wire for low, they should be pin 16 and 17. Check those two wires for voltage when the switch is in those positions. You should check them both at both high and low just in case i'm wrong about which is high and low. If neither of them have voltage that doesn't mean it's bad. The wires should be nothing or power at rest and ground in high or low so take your meter and again set to ohms put one lead on a good ground and probe the wires with the other. In high and low you should read 0 ohms on the orange in high and brown in low. if the wires are going to ground the GEM is good and you need to move on to the relay.]
Everything checked out til i checked the wiring at the t case motor. Those wires did not ohm out at 0. Does that mean the gem is at fault? Ib also went a step further and checked the solenoids. The solenoids themselves are fine but when you turn the switch from 2h - 4h the voltage stays on the disengage solenoid. It will randomly work but if does happen to go in 4wd it don't want to come back out. I have to repeatedly turn the truck off and back on till it will finally receive the signal to disengage.
[So now you've got to rule things out. First things first, check fuse 17 under the hood and fuse 12 under the dash. Then I would use a volt meter to first check that there is power at pin 3 then measure the resistance between the two dark blue wires at the switch, pin 3 and pin 2. The three positions of the switch should read 3.9k, 1.1k and 360 ohms. If they aren't then you have a bad switch.
If the switch is good you need to make sure the GEM is outputting the ground signals to activate the relay that shifts the t-case motor. Orange/light blue is the wire for high and brown/white is the wire for low, they should be pin 16 and 17. Check those two wires for voltage when the switch is in those positions. You should check them both at both high and low just in case i'm wrong about which is high and low. If neither of them have voltage that doesn't mean it's bad. The wires should be nothing or power at rest and ground in high or low so take your meter and again set to ohms put one lead on a good ground and probe the wires with the other. In high and low you should read 0 ohms on the orange in high and brown in low. if the wires are going to ground the GEM is good and you need to move on to the relay.]
Everything checked out til i checked the wiring at the t case motor. Those wires did not ohm out at 0. Does that mean the gem is at fault? Ib also went a step further and checked the solenoids. The solenoids themselves are fine but when you turn the switch from 2h - 4h the voltage stays on the disengage solenoid. It will randomly work but if does happen to go in 4wd it don't want to come back out. I have to repeatedly turn the truck off and back on till it will finally receive the signal to disengage.
nobody has any info?