Toyota Low-Range Locking
Q:I own an '02 Tacoma with the locking differential. It only locks in 4Low. The 2WD TRD Tacoma can lock its rear differential, so why can't I lock mine in 4High? I saw a modification on a Web site where you can cut a wire, and it allows you to lock it in 4High, 4Low, and 2WD. I'm wondering if this would damage the truck or if Toyota set this up as a safety precaution. It's a bad thing to drive on pavement with it locked, but it would help to have power going to the rear wheels when off-road and not being limited to only five mph.
A: I looked over the modification you're referring to, and it involves cutting and grounding a gray wire between the Engine Control Module and the 4WD Control Module. This provides a false signal of four-wheel-low transfer-case engagement to the 4WD control unit, and, in turn, will activate the locking differential regardless of 4WD operation. But I don't see how this affects the speed limitation of five mph, which is determined by vehicle speed sensor data regardless of transfer-case engagement. Toyota's full locking differential is designed for low-speed off-road operation, and common sense tells us that they activate the system only in L4 on the 4x4 models because you should be using it only in the lowest gearing available for your particular truck. This option supplies a solid mechanical lock between the two rear axles, and use under high speeds or good-traction conditions will result in damage to an axle and/or differential. I advise not messing with the system. The locking differential does a great job of slowly pulling you out of a poor-traction situation where it wouldn't make sense to be in anything but 4Low.
How To Reach Alex
If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, who is a master technician with the National Institute for Automotive Service Excellence. Send a letter or e mail him in care of Truck Trend Garage at:
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Trapped from the Inside
Q: The power door locks on my '97 Ford Expedition have always had the option of locking automatically when you start driving away. This makes me feel more secure while the kids are in the back, and I don't have to remember to lock the doors each time we go somewhere. Now the automatic locking has stopped working, but the normal power door locks work fine. Is there a way I can reset the automatic locks before I have to see the dealer?
A: This may get complicated, but hang in there. The Autolock/Relock part of your keyless-entry system works like this: Once the ignition is in the Run or Accessory position, the transmission-gear selector has gone in and out of the Reverse position, and the brake pedal is released with all doors closed, all the doors will then lock automatically. Relock refers to the action of any door being opened and closed, after the initial lock, and then automatically Relocked with the release of the brake pedal. This entire system is controlled by the RAP (Remote Anti-theft Personality) module. The Autolock/ Relock feature is turned on at the factory, but any time battery power is lost, the RAP module will reset to the disabled position. So, if you've had a dead battery, replaced the battery, or if someone has temporarily disconnected the battery, this would explain the problem. The enable/disable procedure should be the first place to start before locating a failure within the system. Hop in and close all the doors with the ignition off, and then do the following within 30 seconds: Ignition on, press the power door-lock unlock button three times, ignition off, press the unlock button three more times. You should hear the RAP module chirp the horn indicating we're now in the enable/disable mode. Next, press the unlock button once to enable the system and then the lock button once to officially enter the command. You should then hear a short chirp followed by a longer honk indicating the Autolock/Relock feature is officially turned on. If you get only the short chirp, the system is disabled, and you must again press the unlock button followed by the lock button once. The RAP module should then chirp and honk showing the system in the enabled state. Turning the ignition off is all that's needed to end the process with the new settings. If this procedure doesn't get you going, there's a failure that will require a qualified technician to track.