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Thread: Troubleshooting the Toyota FJ80 Land Cruiser Center Diff Lock (CDL)

              
   
   
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  1. #1
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    Default Troubleshooting the Toyota FJ80 Land Cruiser Center Diff Lock (CDL)

    <center><a href="http://photography.pnwadventures.com/picture.php?/300531747/" title="Toyota FJ80 Land Cruiser"><img src="http://farm1.static.flickr.com/100/300531747_973ee1f550.jpg" alt="Toyota FJ80 Land Cruiser" /></a></center>

    When I purchased my 1992 Toyota FJ80 Land Cruiser, the previous owner informed me that the four wheel drive system did not work. I knew the transfer case was a rebuilt unit so I figured it would be something simple such as a switch or a relay. Little did I know that I would spend hours trying to troubleshoot the problem. Hopefully this article will walk you through all the diagnostics needed to check the complete center diff lock (CDL) electrical system so you can figure out the problem much faster than I did.

    You might ask, why did you spend hours diagnosing the problem? My answer is, I don't like to spend money replacing parts when the part being replaced was not the problem. I've been a victim of paying people to do just that. Never again.

    As in all repairs on the Land Cruiser, you should purchase the factory Toyota Repair Manual and the Toyota Electrical Wiring Diagram for your specific year of vehicle (order the factory manuals at <a href="http://techinfo.toyota.com/" target="_blank">techinfo.toyota.com</a>). A Chilton's or similar service manual won't cut it when you are diagnosing specific issues. Invest the money in the factory manuals. It's worth it if you (or your mechanic) does any diagnostics or repairs on your Land Cruiser. Purchasing the correct manual will pay off only after a few repairs because you will be diagnosing problems and not throwing parts at the problem until it is fixed. The reference for this article was the USA version for 1992 model year Toyota Land Cruiser. Even though there are similarities between all 80-series, there are differences between the various years of Land Cruisers and world markets so be aware of this when making repairs to your Land Cruiser.
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    <center><a href="http://www.flickr.com/photos/locked4low/2042398594/" title="Toyota Repair Manual"><img src="http://farm3.static.flickr.com/2079/2042398594_165ee287a0.jpg" width="500" height="375" alt="Toyota Repair Manual" /></a></center>

    The factory service manual is not the end all of diagnosing your FJ80 Land Cruiser. Experience (or the experience of others) is a valuable asset to have when diagnosing problems on your vehicle. One of the best online resources that fills in the blanks where the Toyota factory manual leaves off is the 80-series on <a href="http://www.ih8mud.com/" target="_blank">ih8mud.com</a>. I think I would still be scratching my head over the CDL if it had not been for the wisdom contained on the 80-series forum on ih8mud.

    In order to make any repairs to the CDL, its a good idea to learn a little how the CDL system works on the 80-series Land Cruiser. I'll try to use the terminology used in the Toyota Land Cruiser factory service manual (1992 model year).
    Last edited by Steve; 05-03-2016 at 10:59.
    Steve

    K9PNW | Exploring the Pacific Northwest in my 1992 Toyota FJ80 Land Cruiser

    Pacific Northwest Backroad Adventures - Pacific Northwest Outdoor Adventure Forums

    Steve G. Bisig Photography
    - Pacific Northwest Photography: Nature, Landscapes, Rural, Urban

  2. #2
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    <h3>The 80-series Land Cruiser Center Differential System</h3>

    As you probably already know, the FJ80 Land Cruiser is a full-time four wheel drive (4WD) system that is equipped with a mechanical lock type center differential system. With the CDL unlocked (normal driving), the open center differential (transfer case) allows the driveshafts to turn at different speeds so when you are turning on a hard surface there is no binding. When you engage (lock) your CDL, it splits the power 50/50 to the front and rear driveshafts regardless of the surface you're driving on or if you are turning. For a detailed explanation on how your 4WD system works, see <a href="http://www.lcool.org/technical/diffs/diffs.html" target="_blank">Diffs for Dummies</a>.

    <center><a href="http://photography.pnwadventures.com/picture.php?/300531562/" title="Toyota FJ80 Land Cruiser Center Diff Lock (CDL) Switch"><img src="http://farm1.static.flickr.com/102/300531562_86502d2364.jpg" alt="Toyota FJ80 Land Cruiser Center Diff Lock (CDL) Switch" /></a><br /><strong>Toyota FJ80 Land Cruiser Center Diff Lock (CDL) Switch</strong></center>

    In the passenger compartment, within reach of the driver, the CDL components you see include the instrument panel 4WD Indicator Light, the Center Differential Lock Switch (stock only on 3FE powered 80-series in the US but can easily be added to 93-97 models) and Transfer Case Select Lever.

    The other components of the CDL system include the Center Diff Lock Control Relay, the 4WD Indicator Switch, the Transfer Neutral Position Switch, the Transfer L4 Position Switch and the Transfer Control Motor Actuator.

    The brain of the system is the Center Diff Lock Control Relay which is located inside the vehicle on the driver's side kick panel. My relay was labled Transmission Relay. Without this relay, you will not be able to engage the 4WD from your cab.

    <center><a href="http://photography.pnwadventures.com/picture.php?/300530365/" title="Toyota FJ80 Land Cruiser Center Diff Lock Control Relay"><img src="http://farm1.static.flickr.com/119/300530365_b4940e01a3.jpg" alt="Toyota FJ80 Land Cruiser Center Diff Lock Control Relay" /></a><br /><strong>Toyota FJ80 Land Cruiser Center Diff Lock Control Relay</strong></center>

    Refer to the <a href="http://www.pnwadventures.com/images/cdl_wiring_1.jpg" target="_blank" title="Toyota FJ80 Land Cruiser Center Diff Lock Wiring Diagram">wiring diagram</a> to follow along.

    Power to the CDL relay is sent from three separate sources. The first power source (Terminal 3 on the relay) is from the 30 amp fuse in the dash fuse box labeld "Diff". This power source should be hot at all times the ignition is on. Within the CDL relay, this power is sent to two small internal relays - normally in the closed position. Input from the two switches described below will change the polarity to the Transfer Control Motor Actuator. The reversal of polarity on the actuator is what engages and disengages the transfer case.

    The second power source (Terminal 7 on the relay) is from the Transfer L4 Position Switch (located on the top rear housing of the transfer case - right side). The Transfer L4 Position Switch receives its power from the 10 amp fuse located inside the passenger compartment fuse panel and labeled "Gauge". When you shift your Transfer Case Select Lever into low range, the L4 switch sends a signal to the CDL relay which first overrides the input from the Center Diff Lock Dash Switch and then closes an internal relay and sends 12 volts from Terminal 1 of the relay through the harness to Terminal 3 of the actuator motor which engages the center diff lock (transfer case) into 4WD. If you have the Center Diff Lock Switch, you can disconnect this wire from the relay in order to have true manual control over the CDL. See <a href="http://www.sleeoffroad.com/technical/tz_cdl_pin7mod.htm" target="_blank">Center Differential Lock Pin 7 Mod</a> for specific instructions on this modification.

    <center><a href="http://photography.pnwadventures.com/picture.php?/312269423/" title="Toyota FJ80 land Cruiser Transfer L4 Position Switch"><img src="http://farm1.static.flickr.com/99/312269423_4ebd798b22.jpg" alt="Toyota FJ80 land Cruiser Transfer L4 Position Switch" /></a><br /><strong>Toyota FJ80 land Cruiser Transfer L4 Position Switch</strong></center>

    The third power source for the CDL relay comes from the Center Diff Lock Dash Switch. Power to the switch is from the same 10 amp fuse previously mentioned. When the switch is on (CDL engaged), you will have 12 volt to Terminal 6 of the CDL relay. When the switch is off, there will be 12 volts to Terminal 9 of the CDL relay. Turning the switch on sends 12 volts from Terminal 1 of the relay through the harness to Terminal 3 of the actuator motor. Turning the switch off sends 12 volts (reversing the polarity) from Terminal 4 of the relay through the harness to Terminal 2 of the actuator motor. Unless you made the Pin 7 mod described above, this switch only engages the CDL when the center diff is in high range.

    When you enage the CDL, either through the Center Diff Lock Dash Switch or through the 4 low range shift lever, the 4WD Indicator Switch (located on the front housing of your transfer case) is activated and provides a signal to the 4WD indicator light on your instrument panel. There is also a Transfer Neutral Position Switch (located next to the Transfer L4 Position Switch - drivers side) that provides a signal to the A/T indicator light on your instrument panel to tell the driver that the transfer case is in neutral.
    Steve

    K9PNW | Exploring the Pacific Northwest in my 1992 Toyota FJ80 Land Cruiser

    Pacific Northwest Backroad Adventures - Pacific Northwest Outdoor Adventure Forums

    Steve G. Bisig Photography
    - Pacific Northwest Photography: Nature, Landscapes, Rural, Urban

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