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Old 04-24-2022, 01:52 PM
stan65 stan65 is offline
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Default CRC-1000 Dakota Digital DBW Cruise and a GMPP LT4

All,

I'm trying to get my cruise to work and I have a strange anomaly.

The cruise only functions when I have my HP-Tuners MPVI2 plugged in. I do not have to have the laptop USB hooked up, just the MPVI2 dongle.

It took me a bit to figure out why it worked sometimes and not others.

If I start the car without the dongle and go for a drive, the cruise will not engage. The light on the CRC-1000 goes green when powered on and turns amber for a second and back to green when I attempt to engage. (Dakota tech support says something is not allowing it to engage, and I would have to agree with them) lol.

If I start the car with the dongle and go for a drive, the cruise will not engage. and function perfectly. The light on the CRC-1000 goes green when powered on and when engaged turns amber and stays amber until I hit the brake or clutch at which time it goes back to green. If I unplug the dongle while driving, it will immediately shut the cruise off.

Any suggestions or explanations?

I tried adding a 60ohm terminating resistor across pins 6 and 14 at the ALDL with no success.

Thanks,
Stan
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  #2  
Old 04-24-2022, 06:16 PM
blitzer454 blitzer454 is online now
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How do you have the brake and clutch inputs to the CRC-1000 connected. My guess is that you need to add a pull-up resistor on one or the other or both.
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Old 04-25-2022, 04:47 AM
srode1 srode1 is online now
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Are you sure the CRC-1000 works with your LT4 E92 controller? I thought it only works with the E38 controller, but could be wrong. I ordered the CRC-2000 instead after talking with Dakota Digital about compatibility.
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Old 04-25-2022, 05:58 PM
blitzer454 blitzer454 is online now
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Both models will work but I think the problem will still be present with the CRC-2000. I think the root problem is that the input I/O cell on the controller chip is an open drain I/O cell that has not been connected properly. If you were to measure the voltage on an open drain I/O cell with nothing connected to it the voltage would be indeterminate. It could be at 0V or maybe the same as the battery voltage or anywhere in between.

So for example if you have a clutch switch such that when the clutch pedal is pressed the switch closes and completes a circuit to ground and you connected this switch to the CRC-1000 without a pull-up resistor the voltage at the I/O cell before the clutch pedal is pressed will be indeterminate and if that voltage happens to be below the ON threshold (active low input) then the controller would think the clutch pedal is being pressed even when it is not and the cruise would not engage.

A possible reason why the cruise only works when the MPVI2 is plugged in is because that circuit shares a common ground with the CRC-1000 which can change the indeterminate voltage just enough such that the normal voltage before the clutch pedal is pressed is just above the ON threshold and everything works. But most likely you would probably see some random failures even with the MPVI2 plugged in as changes in operating temp, humidity etc.. could change the voltage just enough to cause it to fail. So in this example the fix would be to add a pull-up resistor to the battery on the I/O cell such that there is no indeterminate voltage before the clutch pedal is pressed.
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