No 4x4 with codes
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Fleet Mechanic
Joined: Jul 2003
Posts: 1,815
Likes: 24
From: Houston
No 4x4 with codes
I've got a 2002 7.3 cc 4x4...well it should be 4x4. I've got no 4wd at all. The 4x4/low range dash lights do not come on when switching to 4wd. They do work though, because I see them when I start up the truck. I've checked the fuses and all are okay. I've swapped the relays and nothing changed. I assume I have power back to the transfer case motor because with KOEO I switch to 4h and can hear the transfer case motor clicking. I also assume that means the switch on the dash is fine. I may be assuming far too much.
The codes I have are:
P1876: Transfer Case 2-Wheel Drive Solenoid Circuit Failure
P1867: Transfer Case Contact Plate General Circuit Failure
C1728: Transfer Case unable to transition between 2H and 4H
I also have manual Mile Marker hubs.
Any thoughts.
Kyle
The codes I have are:
P1876: Transfer Case 2-Wheel Drive Solenoid Circuit Failure
P1867: Transfer Case Contact Plate General Circuit Failure
C1728: Transfer Case unable to transition between 2H and 4H
I also have manual Mile Marker hubs.
Any thoughts.
Kyle
Post Fiend
Joined: Nov 2007
Posts: 9,549
Likes: 14
From: Payson, AZ
The first thing is to make sure that both hubs are locking. If one does not then you will not have front wheel drive because the front is an open diff which means that only the axle with the unlocked hub will turn.
EDIT:
But from the codes it seems your probem is electrical.
Bench test the ESOF relays. Make sure the normally closed contacts have continuity with relay non-operated and if the relay operates that the closed contacts have continuity. Do not swap these 5 pinterminal relays with a 4 terminal relay because for the ESOF to work the normally closed contacts are needed in the circuit. Also, while the relays are in the truck have someone switch to 4 Hi and 4 low while you have a finger on the relays so you can feel them operate.
EDIT:
But from the codes it seems your probem is electrical.
Bench test the ESOF relays. Make sure the normally closed contacts have continuity with relay non-operated and if the relay operates that the closed contacts have continuity. Do not swap these 5 pinterminal relays with a 4 terminal relay because for the ESOF to work the normally closed contacts are needed in the circuit. Also, while the relays are in the truck have someone switch to 4 Hi and 4 low while you have a finger on the relays so you can feel them operate.
Thread Starter
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Fleet Mechanic
Joined: Jul 2003
Posts: 1,815
Likes: 24
From: Houston
PaysonPSD,
I have a couple of new relays I can swap out when I get home. I also pm'd dchamberlain and he suggested I do the test light test on the two pin harness at the tcase motor. I'm going to do that when I get home and see what happens.
Thanks for all the thoughts.
Post Fiend
Joined: Nov 2007
Posts: 9,549
Likes: 14
From: Payson, AZ
This should have been my first post or at least included in my first post.
I had a similar problem and the relays bench tested ok. Before putting them back in I cleaned the relay terminals and the relay mounting sockets with emory cloth and the problem was gone. Still problem free for over 2 years.
I had a similar problem and the relays bench tested ok. Before putting them back in I cleaned the relay terminals and the relay mounting sockets with emory cloth and the problem was gone. Still problem free for over 2 years.
Post Fiend
Joined: Sep 2006
Posts: 7,426
Likes: 6
From: Sioux Falls, SD
With my Excursion one of the wires pulled out a bit from the harness plug. but that only caused the P1876 code
P1876: Transfer Case 2-Wheel Drive Solenoid Circuit Failure
Between dchamberlain and Robin's recommendations you'll find the problem.
P1876: Transfer Case 2-Wheel Drive Solenoid Circuit Failure
Between dchamberlain and Robin's recommendations you'll find the problem.
Thread Starter
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Fleet Mechanic
Joined: Jul 2003
Posts: 1,815
Likes: 24
From: Houston
Update:
I tried the test light on the 2 pin harness at the tcase motor and got no flash of light. I tried it probably 20 times. My 8 year old son thought I was crazy asking him to keep switching between 2h and 4h. This only needs to be KOEO to work correct?
I also put 2 brand new relays in that I had.
Today I will take a look at the switch on the dash and see if it has voltage.
Any other thoughts?
I tried the test light on the 2 pin harness at the tcase motor and got no flash of light. I tried it probably 20 times. My 8 year old son thought I was crazy asking him to keep switching between 2h and 4h. This only needs to be KOEO to work correct?
I also put 2 brand new relays in that I had.
Today I will take a look at the switch on the dash and see if it has voltage.
Any other thoughts?
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Fleet Mechanic
Joined: Jul 2003
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From: Houston
Update:
I went outside and pulled the ESOF switch out of the dash. I thought I might as well check fuses one more time. I don't know if I missed fuse 31 or what, but it is only getting .28v across to the fuse. This fuse is a 15A fuse and is labeled "Shift Lock" on Alldata.
Any thoughts on that?
I went outside and pulled the ESOF switch out of the dash. I thought I might as well check fuses one more time. I don't know if I missed fuse 31 or what, but it is only getting .28v across to the fuse. This fuse is a 15A fuse and is labeled "Shift Lock" on Alldata.
Any thoughts on that?
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Fleet Mechanic
Joined: Jul 2003
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From: Houston
Update 3:
I tested the ESOF switch and got the following
When Disconnected from switch
Pin 1: 12v (Illumination)
Pin 2: 12v comes from the 4wd control module
Pin 3: NOTHING
Pin 4: Ground
When Connected to the switch (probed from backside)
Pin 1: 12v (Illumination)
Pin 2: 5.5v drops to 2.Xv when switched to 4x4 high
Pin 3: NOTHING
Pin 4: Ground
I traced pin 3 back to the 4wd control module and it is described as "ESOF reference voltage".
How do I test the switch itself?
I tested the ESOF switch and got the following
When Disconnected from switch
Pin 1: 12v (Illumination)
Pin 2: 12v comes from the 4wd control module
Pin 3: NOTHING
Pin 4: Ground
When Connected to the switch (probed from backside)
Pin 1: 12v (Illumination)
Pin 2: 5.5v drops to 2.Xv when switched to 4x4 high
Pin 3: NOTHING
Pin 4: Ground
I traced pin 3 back to the 4wd control module and it is described as "ESOF reference voltage".
How do I test the switch itself?
Lead Driver
Joined: Sep 2007
Posts: 8,180
Likes: 669
From: Scio, OR
Fuse 31 is hot in start, which means it will only see power when cranking. I'm not sure why they are using a hot in start supply, but that is what the diagram says.
What you are seeing at the switch seems correct. Pin 1 and 4 are illumination. The switch should apply a different resistance value in each switch position between pins 2 and 3.
Make sure you are looking at the right relays. On mine, they are two identical relays by themselves in a relay box. Put your finger on them and see if one of them is clicking while someone is turning the switch.
The codes you have indicate that the computer is getting bad information back from the encoder. I wonder if the computer is smart enough to "shut down" because of that. It's entirely wild *** speculation on my part, but it might be interesting to disconnect the encoder (the 5 wire connector to the shift motor), reset the computers by disconnecting the batteries for awhile, and then trying the test light on the 2 pin connector test again.
What you are seeing at the switch seems correct. Pin 1 and 4 are illumination. The switch should apply a different resistance value in each switch position between pins 2 and 3.
Make sure you are looking at the right relays. On mine, they are two identical relays by themselves in a relay box. Put your finger on them and see if one of them is clicking while someone is turning the switch.
The codes you have indicate that the computer is getting bad information back from the encoder. I wonder if the computer is smart enough to "shut down" because of that. It's entirely wild *** speculation on my part, but it might be interesting to disconnect the encoder (the 5 wire connector to the shift motor), reset the computers by disconnecting the batteries for awhile, and then trying the test light on the 2 pin connector test again.
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Fleet Mechanic
Joined: Jul 2003
Posts: 1,815
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From: Houston
I went out and checked the relays again. I can turn the dash switch and feel nothing happening in either relay.
I'm pretty sure these are the correct relays. I have two seperate relay boxes under the hood. This one contains 2 identical 5 terminal relays. The other contains a 5 terminal relay and two smaller relays (according to Alldata these are trailer tow right/left and AC clutch relays).
I'm pretty sure these are the correct relays. I have two seperate relay boxes under the hood. This one contains 2 identical 5 terminal relays. The other contains a 5 terminal relay and two smaller relays (according to Alldata these are trailer tow right/left and AC clutch relays).
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