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Discussion Starter #1 (Edited by Moderator)
Here's a little something for all you guys who swapped in a VQ and can't stay off the gas on the highway like me: CRUISE CONTROL

So I finally got around to looking at this on my car (turbo vq swapped by Travis) and the solution is pretty easy and straight forward. The reason it didn't work was because the cruise control switch was not the same as the switch my ecu expected to see. I have a maxima ecu in my car and you'll see below the resistances my ecu wants to see when each button is pressed is not the same as a stock sentra. Before you do this to your car get the factory manuals for your year sentra as well as for the year and model ecu you have (stay tuned has them all available on their site). This information is from the EC section for DTC P1564 in each service manual.

2003 Maxima resistances:


2003 Sentra resistances:


These differences can be fixed by adding resistors to your steering switch. To figure out what values you need you have to understand equivalent resistances of resistors in parallel and resistors in series. Go here if you do not:
Resistor - Wikipedia, the free encyclopedia

My car's switch was actually different than the manual indicates it should be.
Nothing pressed = infinite resistance
Set/Coast = 1496 ohms
Cancel = 5.06k ohms
Acc/Res = 3.29k ohms
On/off = 0 ohms

You will have to measure your switch to see what it does and then use this information to determine what resistors you need to add. These instructions assume your switch acts like mine and you have a 2003 5spd maxima ecu.

Looking at your steering switch you will see three resistors on the side that faces in as well as various holes in the plastic to contact the lines (wires) underneath. In the stock configuration (my car) the resistance across the pins of the unit is infinite when no buttons are pressed, 0 ohms when on/off is pressed, and is the value of one of the resistors when one of the other three buttons is pressed. See below:



The first thing you need to do is add a 4k resistance across the pins of the switch so that the resistance is 4k when nothing is pressed instead of infinity. You'll find that if you test the different contact holes with a multi meter you can find one that is connected directly to each pin. Do not use the contacts that have holes drilled through the hole. These holes are drilled through the line to break it. You'll see what I am talking about in the picture below of what I did.

Next you have to change the resistances of each button press. I chose to add additional resistors in parallel on the opposite side of the board of the stock ones to achieve the right values. I did this because there is plenty of space to work with under the plastic cover on this side of the unit when it is installed on the wheel again. You can remove the stock resistors and put the value needed (without being parallelled with the stock value) on either side of the board if you want instead.

Below is my soldering job. If you do this I highly recommend using solder flux as I did not and it was very difficult to make the solder stick to the board and I melted some plastic. No big deal but it was a pain in the butt.



As you can see the values I used aren't in the tables. wtf did I do? I had to calculate the value I needed which would produce a resistance in the table when in parallel with the stock resistor and the 4k resistor I added.

For example I have 1.7k ohms on the Set/Coast Button. The equation is:
Req = (1/R1+1/R2+1/R3)^(-1)
R1 = 1.7k
R2 = 1496 (stock resistor value I measured with multi meter)
R3 = 4k (resistor I added across the pins of the switch)

Req = 1/(0.00058824 + 0.00066845 + 0.00025) = 1/(0.001507) = 663.709

Close enough to 660 ohms.

Note that for on/off 0 ohms paralleled with 4k is still 0 ohms.

After you calculate all your values and solder everything test your work with your multi meter to be sure you get the right resistances through the switch as whole when each button is pressed and when nothing is pressed.

After you've done all this you can slap it in the car if your switch is still connected to the ecu.

If it is not you have to get it reconnected. I ran a new wire after looking at the wire harness for a short time and not finding where the ecu wire was tied to resistors to disable it. The wire you need on the sentra side (again consult your manuals for your sentra and ecu you have to be sure you have the same colors I do) is a solid green one in a small bundle that goes to the right under the steering wheel:



For my car on the ecu side the wire I connected to was green with a yellow stripe coming from pin 50. There is a wiring diagram in each manual of the circuit for DTC P1564 in the EC section.

After all of this is done cruise will work on your car. On my car the indicator lights for cruise do not illuminate. I am not sure if these are connected or not in my wire harness but I don't really care because I don't like the lights at night anyway.

If you look at the ASCD Indicator section from EC in each manual the maxima has load resistors inline with the leds to limit current and the sentra does not. This may be why my lights don't work but I don't care to pull the ecu out and chase wires to find out.

If you guys have questions about this you can message me or reply. I'll help to figure out your unit if it is radically different.

- James
 

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This doesn't pertain to me at all, but is still an awesome and respectable write-up. Great job!
 

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Thanks for the write-up, James.. :)

You did the one thing that I never thought to do, which is to compare the switches themselves. lol!
 

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Installed an aftermarket steering wheel, just want my cruise control back.
Driving me crazy!
 
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