Nissan 2006 Maxima Navigation Unit "Hack" to Enable Passenger Destination Programming While the Car is Moving

--- The Problem:

All 2006 Maxima owners know, should they have a navigation system installed, you can’t program a new GPS location when you’re moving. This happens because, when the car is in motion, a unit called the “Unified Meter and A/C Amp” module puts out a signal called the Vehicle Speed Signal (commonly called the VSS signal) on its connector pin #26. This signal is read by the navigation module on its pin #66 as well as by the display control unit on its pin #16. Among other things, the navigation and blue tooth units use this signal to disable certain of their functions while the car is in motion – things like programming a destination or changing a cell phone directory entry.

--- The Solution:

This write up is a set of instructions describing how to install a switch on the VSS signal output from the “Unified Meter and A/C Amp” module to fool the navigation system into believing the car is not in motion thereby allowing a new GPS location to be entered while in motion.

--- The Parking Brake Signal:

I found other “hacks” on the Internet describing other model year Maxima’s that require an additional modification “ground” a parking brake signal that somehow informs the GPS system you are not in motion because the parking brake is engaged. I could find no such a parking brake signal in all the 2006 Maxima wiring diagrams I looked at (on this web site) so I assume such a signal does not exist in the 2006 Maxima.

--- Getting inside the dash:

The following is a set of instructions on how to open your dash and get at the VSS wire and install a switch. If you want pictures, Crutchfield will sell you a set for $10.00. I didn’t take pictures as I performed my modification and I’m not about to do the job again just to make them. So you’ll have to get pictures elsewhere such as from Crutchfield – which is what I used. Verbal instructions follow. Good luck.
1. Remove the clip on the bottom side of the shifter knob.
2. Remove the shifter knob and spacer.
3. Pry the shifter trim plate up from the rear (go in from the front of the cub holder) with a screwdriver. (Note: It may be necessary to turn the ignition on, apply the brake, and move the shifter knob to a rear position in order for the plate to clear the shifter shaft.)
4. Remove the 2 phillips screws from the bottom of the CD/tape player trim plate.
5. Lift the trim plate up from the bottom an inch or two and then pull the plate’s retaining clips out from the top.
6. Disconnect its ribbon cable.
7. Remove 2 phillips screws from the bottom of the “display control / heater vents” panel.
8. Lift the panel together with its heater vents up from the bottom until you can free the hidden hooks at the top.
9. Disconnect its cable connection coming through the hole in the radio/heater rack assembly.
10. Remove 4 screws holding the radio/heater rack assembly. Notice the top 2 screw are sintered metal. They’re special because they ground the rack assembly to vehicle ground – be sure to reassembly them properly later.
11. Remove the 2 bolts attaching the navigation module at the bottom.
12. Remove the radio/heater rack assembly. I found I had to leave the navigation module behind as I removed the rack assembly because it had a cable connection at the back which I was not able to get at and unplug.
13. Remove all the connectors from the rack assembly. Easy to say – difficult to do. Don’t worry about keeping track of which connector goes where. They’re all unique and can only be reassembled one way.

--- What’s in the Radio/Heater rack assembly

In 2006 Maxima’s with navigation the radio/heater rack assembly rack has six modules. From top to bottom they are ...
1. The Display
2. The Unified Meter and A/C Amp.
3. The Automatic Drive Position Control Unit.
4. The Display Control Unit.
5. The Audio (Radio, CD, Tape, Stereo, etc) Unit.
6. The navigation unit (which I left behind in the dash).

--- The wire that needs to be cut and switched:

The source of the VSS signal we want to control is the "Unified Meter and A/C Amp" Unit. I found two of its plugs to be gray in color. (All others in the whole rack were white.) They were located side by side, one being a 20 pin connector, and the other being a 16 pins. On the 16-pin connector, looking into the contacts, the subject pin 26 will be the third pin in from the left on the top row. (Numbering begins with the 20-pin connector for pins from 1 to 20 and the 16-pin connector continues with 21 in the upper right and numbers to the left in the top row and finishes in the bottom row.) The VSS wire is brown. Cut it in the middle of the exposed area to allow for easy working. Splice in your two wire leads to your switch. Install your switch and run your leads to it. (I installed my switch on the right inside the cubby behind the shifter – in front of the navigation CD drive.)

When the job is done, put everything back together. You’re done.

--- How the Maxima navigation system works:

Contrary to popular opinion, the Maxima Navigation display is not driven directly by the GPS system but rather by a somewhat sophisticated dead-reckoning system. A dead-reckoning system is one where you keep track of your position on a map and track your movements by speed and direction. For example, if you’re traveling north at a speed of 60 miles an hour for one minute then you will end up 1 mile north of your start point. Dead-reckoning is how sailors navigated before GPS’s came along.

The Nissan system keeps track of where you are at all times – even when the ignition is off – because it saves your position when you turn your ignition off. What’s more, have you ever wondered how the Navigation system continues to show your car progressing down the road as it travels through a long and curvy tunnel? Garmin and Magellan units require a view of the sky to work which means they don’t when you’re in a tunnel. The Maxima navigation system keeps track of your position by dead-reakoning using its compass and speed (VSS) data. The Nissan wiring diagrams also mention a rotational inertia sensor but I’m sure its data comes from the same compass and VSS source data. The navigation unit does a really good job of tracking of the cars location, providing a smooth continuous readout on the screen even without a view of the sky. The problem is, bye-and-bye, location errors stack up in a dead-reckoning system and accuracy will wane. Just ask Chris Columbus – he ended up in the Caribbean.

GPS to the rescue. From time to time, when in view of the sky, the GPS unit makes adjustments to the dead-reckoning system to keep its location accurate. But, you don’t want to give total and full control of the nav system to the GPS because of – well – the tunnel problem.

--- Switch Operation:

Be prepared for funny things to happen when you throw your switch. When your passenger does so to reprogram a new destination, the dead-reckoning system will think you stopped dead in your tracks at 0 mph. However, the compass input to the navigation unit will continue to work feeding the navigation system with direction direction. You’ll notice on your screen that your car will spin on a dime as you make turns. Not until you throw the switch back will the system begin its recovery process. Remember, it’s designed to maintain a smooth flow on the screen and to make small adjustment tweaks to the location to keep things accurate. I’ve seen several small adjustments happen. Then again, I’ve seen big jumps to the correct location. Whatever the case, be patient, the dead-reckoning system will eventually sync with your true GPS location. And remember, in these moments, you’re no worse off than if you’ve just turned on an inexpensive Garmin or Magellan unit when they go through their process of calculating their location by reacquiring satellite communications, downloading satellite location data, resetting their GPS communication clock, and all so they can ultimately calculate their location - which takes time.

Enjoy.
Al Foote

Awesome write up! Thanks.

I'll add it to the how-to's.

I've been prompted to add this note about the speedometer. Specifically, it doesn't work when the switch is thrown because it uses the same signal. But the cruise control does continue to work while the speedo goes to zero.

Al