[shawn900]

I noticed my front tires aren't spinning after testing by jacking up the rear end only and switch to awd putting it in Low and only the rear tires spin. So I am trying to test voltage first to the front diff. I disconnected the plug going to the front diff and am testing on the vehicle side of the connector. My question is when checking voltage do you go across the two leads on the connector going into the front diff (one br/wh wire and one rd/dg) or do you put one lead on a chassis ground and the other on the red/dark green wire? When I test it with the meter on the negative battery post and positive one the rd/dg wire I get 12 volts with the awd switch engaged. But if I go across those two connector pins I get no voltage with the awd switch engaged. Seems I would need to go across the two pins since the ECM is what sends a ground signal to Engage the front diff and there would always be 12 volts there if i go to a chassis ground but I'm not sure. I did ohm out the coil and got 24 ohms which is good.

Here is what the manual says as far as testing but it is not clear if you go across the two pins or use a chassis ground.

Turn the ignition switch and AWD switch on and place gear selector in High or Low gear. Check for minimum battery voltage at Gray and Brown/White chassis wires that power the coil. A minimum of 11 Vdc should be present.
3.If electrical tests are within specification, remove gearcase (see “Gearcase Removal”) and inspect components.

 

[Toxic-21]

You also need to check your dash switch.

 

[shawn900]

What is the best way to verify the switch? It does light up when I switch it to AWD and I have 12 volts on pin 3 which is the gray wire. Beyond that not sure how to verify it. I did disconnect it and check for continuity across pins 2/3 and 5/6. Across pins 2/3 has no continuity but 5/6 did when switch was in AWD.

 

[Toxic-21]

What is the best way to verify the switch? It does light up when I switch it to AWD and I have 12 volts on pin 3 which is the gray wire. Beyond that not sure how to verify it. I did disconnect it and check for continuity across pins 2/3 and 5/6. Across pins 2/3 has no continuity but 5/6 did when switch was in AWD.

Shawn, I should have stated that differently, check and make sure you have a minimum of 11 volts on the chassis side of the front gear case connector. Since we are just looking at the front gear case.

It sounds like everything checks out according to your posts.

 

[mx1alex]

I had a similar issue recently. When I would test each wire from chassis side of harness to ground one would test at 12v and the other would test at 3v. When I would test voltage between the two wires directly it would be around 8v. I had to put a new ECU in mine to get it to work.

 

[trog]

you mean it is something inside greg ?

 

[shawn900]

Ok. Do you check it to chassis ground or across to two pins on the plug? Thanks alot for the help.

 

[Seastacker]

You can check voltage on the vehicle side of the plug. You can also check resistance on the gearcase side. Your manual should have steps and specs on this. Also, there are other items that can cause this: A bad 4x4 switch, gear selector switch (does your dash show what gear you are in?). If all the electrical seems to check out, it may be time to drain out the fluid and look for any signs of mechanical failure such as the sprague cage. Being that it is easy, I would probably start with the front diff oil just to rule out anything obvious.

 

[shawn900]

I have verified good resistance at the diff side of the plug which was 24 ohms. The dash shows what gear I am in and also shows it is in AWD. What is the proper way to verify voltage going to the diff? Do I take the reading across the two pins on the vehicle side of the plug or use a chassis ground while checking the voltage on the plug? There is voltage using the chassis as a ground but none if I go across the two pins with the switch in AWD.

 

[Dseldoc]

I have verified good resistance at the diff side of the plug which was 24 ohms. The dash shows what gear I am in and also shows it is in AWD. What is the proper way to verify voltage going to the diff? Do I take the reading across the two pins on the vehicle side of the plug or use a chassis ground while checking the voltage on the plug? There is voltage using the chassis as a ground but none if I go across the two pins with the switch in AWD.

The quick way to see if the ECU is grounding the circuit is to leave the plug connected, use a good chassis ground for your negative meter lead, and take the following readings with the positive meter probe: Backprobe the hot wire from the AWD switch at the drive unit connector with the switch in AWD. Should have battery voltage. Backprobe the wire going to the ECU with the AWD switch on. You should have no more than about 1/10 volt with the AWD energized. Anything more than 0.1v indicates that the circuit is not being grounded. If you can locate and Backprobe the AWD pin at the ECU, make the same voltage tests. Should get the same results (almost zero energized). If you get much more than 0.1v, say 2-3 volts with the AWD energized, unplug the ECU and check the resistance between the (unplugged) terminal at the AWD connector and the AWD driver pin in the ECU connector. You should have a few tenths of an ohm max. Be sure to have the ignition off when connecting/disconnecting anything... If you have very little resistance in the driver wire between the AWD and ECU connectors, and the voltage readings at the AWD connector are good, particularly the 0.1v on the driver side, You've verified the electrical part of the circuit. If the driver wire voltage is high, and the wire resistance is low, the ECU is suspect. If all checks our electrically, time to look at the AWD unit.
If you can't make sense of this, just PM me.

 

[Dseldoc]

You also need to check your dash switch.

This is the diagram of a 2011 900.
Note that the ECU supplies voltage to the switch, and the switch connect the ECU to ground. You can remove the switch to check it or run tests similar to those to verify continuity of the AWD circuit. Backprobe to check voltage at pin 3. With he AWD switch off, you may have 12 or 5 volts, depending on what the ECM uses for reference. With the AWD switch engaged, you should have no more than about 0.1 volts. That's because you are reading the ground side if the circuit. Grounding that wire tells the ECU to ground the wire returning to the ECU from the AWD coil.

 

[Toxic-21]

This is the diagram of a 2011 900.
Note that the ECU supplies voltage to the switch, and the switch connect the ECU to ground. You can remove the switch to check it or run tests similar to those to verify continuity of the AWD circuit. Backprobe to check voltage at pin 3. With he AWD switch off, you may have 12 or 5 volts, depending on what the ECM uses for reference. With the AWD switch engaged, you should have no more than about 0.1 volts. That's because you are reading the ground side if the circuit. Grounding that wire tells the ECU to ground the wire returning to the ECU from the AWD coil.

View attachment 30938

Tom, that is great information, you definitely know your electrical.
Thanks for posting/sharing this.

 

[shawn900]

Just wanted to post an update for those who might have the same issue. My problem ended up being a bad awd switch. Thank you all for your help in troubleshooting this problem. What a great forum.

 

[Dseldoc]

Thanks, Shawn for posting the fix. Everybody learns something that way.

 

[PowerRanger4x4]

Hey Guys Im new here and just got a 2004 Ranger 4x4 500 I have the same issue here I checked it quick tonight and I jacked up all 4 wheels and only rear wheels spin I have voltage to the Red/Green wire on the machine side and no ground on the brown/white wire if I jump the Brown/white wire to ground 4x4 engages perfect so from what I've read the ecm makes the ground for the coil in the diff. so in order for the ecm to make a ground to the diff what has to happen for the ecm to compete the ground so the coil in the diff energizes and locks it into 4x4. I guess tomorrow I will check the switch and make sure I have a good ground to the switch and getting a good ground out if the switch and go from there I just didnt know if the ecm looks for other things like rear wheel speed sensor if there is one or shift indicator in gear etc etc. Does the ecm send a ground to the diff coil as it needs 4x4 or do the locking mechanism in the diff do that when needed the extra traction?

 

[daneek]

I have the same issue it seems on our 2001 Ranger 500. It seems that the brown/white wire going to the voltage regulator (assuming that is the device) is not providing ground and engaging the coil. I've ordered the new regulator but am still unsure that is the problem. What would be the issue connecting the brown/white wire straight to grond?

 

[Mondo_13]

I had a similar issue recently. When I would test each wire from chassis side of harness to ground one would test at 12v and the other would test at 3v. When I would test voltage between the two wires directly it would be around 8v. I had to put a new ECU in mine to get it to work.

Hi there once you replaced the ECM what volts did your chassis plug test out at? I have one that is currently testing 12v on one side and 3v on the other when hooked to a chassis ground? Also my diff coil plug is only reading 2ohms when checking for resistance?

 

[Jungleman]

" Also my diff coil plug is only reading 2ohms when checking for resistance? "..

I would be checking for a bad wire. Right as the wires enter into the case .

Year Ranger ?

 

[Mondo_13]

" Also my diff coil plug is only reading 2ohms when checking for resistance? "..

I would be checking for a bad wire. Right as the wires enter into the case .

Year Ranger ?

2014 Ranger XP 900

 

[Mondo_13]

2014 Ranger XP 900

So I found out I had my ohm meter on the wrong setting so it actually tested at 22.7ohms on the diff coil side so shoukd be good there. Now on chassis side testing with a chassis ground I have 12v on one pin and 3 on the other? If I test across both pins in the plug I have 8v?? Possible switch failure in the dash? I'm not sure how to test the switch?