Hacking the Saturn Cruise Control ...

[Rick Rae]

Originally Posted by cfg83

I think the module just controls a motor that pulls the CC adjuster cable.

This goes back to my earlier confusion. For the CCM I was visualizing a little computer/control circuit that was doing all the cruise control management -- that's why I said the lines seemed reversed to me.

But if it's basically just a motor driver with safety interlocks and the PCM is doing all the thinking, then the lines make sense as shown. In that case, my original guess could very well be right on the mark.

But, the best thing to do is attach a multimeter and see what happens. I keep thinking that this is a job for an oscilliscope or a "voltage logger" (which I guess is another word for oscilliscope).

If you were down this way I'd invite you over. I'm a full-fledged geek and have an oscilloscope, logic analyzer, protocol analyzer, several DMMs... most anything you'd need for the electronics side.

But I think the most valuable thing for your test will be a second set of eyes to watch what happens while you drive down the road and fiddle with the cruise control.

Rick

[skewbe]

Huh, It hadn't occured to me to ask before, but my manual PCM might not have been programmed for cruise control.

Ah well, still knowing what signals what could be useful for putting together a simple "throttle hold" circuit perhaps, that just holds the throttle at a certain position and doesn't try to maintain an exact speed. From what I understand, that is a lot more efficient than typical cruise control if there are any hills involved (and would solve the accelerating on hills thingy).

[cfg83]

skewbe -

Originally Posted by skewbe

Huh, It hadn't occured to me to ask before, but my manual PCM might not have been programmed for cruise control.

Ah well, still knowing what signals what could be useful for putting together a simple "throttle hold" circuit perhaps, that just holds the throttle at a certain position and doesn't try to maintain an exact speed. From what I understand, that is a lot more efficient than typical cruise control if there are any hills involved (and would solve the accelerating on hills thingy).

Hrmmmm, I think that's a saturnfans question. My manual transmission came with CC. I would think that they all are "CC ready". When I have looked at PCMs on ebay, the only differentiator for the PCM seems to be transmission type (auto or stick). No one ever mentions CC as a PCM option.

I seem to recall on saturnfans that a change in the 5th gear would make CC not work properly, but I can't recall the exact post.

CarloSW2

[cfg83]

Rick -

Originally Posted by Rick Rae

This goes back to my earlier confusion. For the CCM I was visualizing a little computer/control circuit that was doing all the cruise control management -- that's why I said the lines seemed reversed to me.

But if it's basically just a motor driver with safety interlocks and the PCM is doing all the thinking, then the lines make sense as shown. In that case, my original guess could very well be right on the mark.

I agree.

If you were down this way I'd invite you over. I'm a full-fledged geek and have an oscilloscope, logic analyzer, protocol analyzer, several DMMs... most anything you'd need for the electronics side.

But I think the most valuable thing for your test will be a second set of eyes to watch what happens while you drive down the road and fiddle with the cruise control.

Rick

I'm a nerd with all the wrong skillz for this stuff. I really wish I had taken a auto repair and electronics course in community college. But, my multi-meter skillz are improving.

Ooooooooh, I just remembered that I will be close to "Signal Electronics" tomorrow. If I am lucky, I will find "the perfect connectors" for the job.

CarloSW2

[diamondlarry]

Originally Posted by cfg83

I keep scavenging these el-cheapo Saturn CD manuals from ebay for $10 and $15 bucks because I don't want to fork out $200 for a real Saturn shop manual CarloSW2

I'll have to look in my Saturn Shop manual and see if I can find the write-up on the CC. My manuals just happen to be for '99 Saturn's.

[cfg83]

Hello -

Here's an update. I wired a tap into the green WOT/IDLE connection and the pink "Move" connection. I only have one multimeter, so I monitored the WOT/IDLE connection on the way to work. Here is what I saw :

Assumption : driving in 5th gear, greater than 30 MPH.

1 - The default floating voltage was 0.45 volts. I suppose this is just normal car electrical noise. I don't think it means anything. I would consider this to be "0.0" voltage for the purpose of the controller.

2 - Whenever I hit the brake, whether the CC was on or off, the reading was a very clean -0.00 volts. This tells me that in addition to the direct signal from the brakes, the ECU/PCM is grounding out the WOT/IDLE wire signal to the CC module. Double-Plus-Good programming redundancy.

3 - When I hit the "Speed Up" button to set the CC speed there would be a sustained 12+ volts(*) and the car would speed up. Pressing the "Speed Up" button when the CC was already set to a certain speed would create a momentary 12+ volts and the car would increase speed by around 1 MPH. If I was going up an incline, the voltage would momentarily go up by itself, but I rarely saw a clean 12+ volts, so I think the signal was very momentary (as compared to slow human pressing button for many a millisecond).

4 - If I hit the "Slow Down" button and CC speed was not already set, there was a momentary 12+ volts, and then the normal 0.45 volts. If CC was already set, it stayed at 0.45 volts.

Cheesy Saturn Cruise Control
Attachment 769

(*) When I say 12+ volts, that is a little misleading. There was large fluctuation in the voltage, anywhere between 4 volts to 13+ volts, but I think this is a function of the multimeter not being able to display the voltage fast enough. When I hit the "Speed Up/Down" buttons for the first time, there was almost always a moment where the voltage when 12+. I think I am going to get an analog multimeter too. This way I will have the best of both worlds.

I will do the "Move" connection next ...

CarloSW2

[cfg83]

diamondlarry -

Originally Posted by diamondlarry

I'll have to look in my Saturn Shop manual and see if I can find the write-up on the CC. My manuals just happen to be for '99 Saturn's.

Coolio, I missed this post from you. It would be nice to see a schematic of the inside of the CC control module. Since it's a $300 retail item and seems to require installation adjustment, I don't want to crack it open.

CarloSW2

[Raccoonjoe]

Keep us up-to-date!! I must have missed this in my searching....as I just posted my own thread asking much the same questions! Guess I get to play with the ol' multi-meter tonight/this week, and see what we can see

[cfg83]

Hello -

Here are my results of monitoring the "MOVE" input line :

- The default state is 12+ volts. This is true whether or not the CC is on or off.

- When the CC is actively set at X MPH, the value is 0.38 volts

- When I hit the Speed Up button on the CC, there is a momentary 1-5 volt jump, and then it goes to 0.38 volts.

- When I hit the Slow Down button on the CC, it goes to 12+ volts. When I release the Slow Down button, it returns to 0.38 volts.

- When I hit the brake, it goes back to 12+ volts.

-------------------------------------------------------------------------

Based on all this information, I think that all I need to do is the following :

1 - Use the wire tap I made to put an ON/OFF switch on the WOT/IDLE input line. Leave in ON position so that CC operates as normal.

2 - Use CC as usual.

3 - When CC is running at a speed and throttle I like, set my custom switch to the OFF position.

4 - Test to see if the "failsafe" inputs disengage the CC when my custom switch is in the OFF position.

5 - Watch for ECU/PCM error codes.

Note : Make sure to use wire and switch rated at 12 volts/5 Amps because that is what the CC fuse is rated at.

From the data I have gathered, I *think* that this will work. This assumes that the 0.45 default voltage I am seeing in the WOT/IDLE line is "electric 0 volts" for the Saturn CC. If this doesn't work, then I think the OFF position will still have to provide the 0.45 volts.

Question : Do you think the "Move" name for the line is short for "move with the accelerator pedal"? Since it's default is 12+ volts and 0.38 volts turns it "off" and locks the pedal in position, that's what I was thinking.

CarloSW2

[cfg83]

Hello -

If you do this test yourself, please don't try to measure the amperage. I thought I would be a super diligent fellow and tell everyone the amperage on each of the lines. However, when I did that, I didn't get a reading and the CC stopped working. I thought I had burned a fuse or some circuit inside the CC or ECU/PCM. However, when I pulled the fuse and re-inserted it and ran the car later on, it worked just fine. Sooooooooo, I think I got lucky.

Whewwww!

CarloSW2