Cruise control mind of its own

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Graculus said:
Two wires through the clockspring to the ECM, the voltage indicates the function requested, the composite speed etc. is already on HS-CAN so other than a 1 or 0 in the CCF, it's not a 'bad' way of doing it, just different.
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We will have to agree to disagree on that. All that is needed is to sample the speed pulses and hold the number in memory when the set button is pressed, then compare that number with regular samples from the speed pulses, Greater than = ease throttle, Less than = increase throttle. A simple software function with NO components other than the 2 wires from the steering wheel..
 
So how is the increase/decrease/suspend/resume signalled - if not on the two wires from the steering wheel?
I think we're at 'crossed wires', the functionality is the same - rather than speed pulses an actual value is read from HS-CAN and the fuelling adjusted accordingly - the control element is a set of expected voltages between 0.5 and 4.5VDC, it's pretty basic and analogue.
 
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This might be a total noob suggestion. But the previous owner fitted 22 inch wheels aftermarket. Would this have this kind of effect in the cruise control due to the amount of distance covered per rotation of the hub being different from standard...... thus is running the risk of making me look very foolish I understand 😅
 
No, unfortunately - it works on a composite measured signal from the ABS, not an 'actual' speed signal.
 
Graculus said:
So how is the increase/decrease/suspend/resume signalled - if not on the two wires from the steering wheel?
I think we're at 'crossed wires', the functionality is the same - rather than speed pulses an actual value is read from HS-CAN and the fuelling adjusted accordingly - the control element is a set of expected voltages between 0.5 and 4.5VDC, it's pretty basic and analogue.
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As can be seen from the OP's post the system is, in the hands of the inexperienced, dangerous in that it can cause unwanted acceleration. Using software for the speed comparison is simple, effective and more reliable. Set, resume and cancel work in the same way in principle, it's just that the reference speed is digital rather than an analogue signal from a resistor pack that most likely has to be converted to digital in order to make a comparison since everything else is digital.
 
It's no different to any other input from a sensor - boost pressure or suspension height for example. All the resistive ladder does is send a specific voltage input to the ECM, which corresponds to an expected function, for example 1V=suspend, 2V=resume etc. a boost pressure sensor does exactly the same, 1V=1Bar, 2V=2Bar etc. the only difference is the boost pressure sensor is a variable output, not a set of fixed (within a % tolerance) values.
I think 'dangerous' is a stretch, given that a simple dab on the brakes or pressing the 'suspend' button will cancel the cruise control function.
The speed value doesn't come from or go through a resistive ladder, it's a composite speed signal broadcast by the ABS on HS-CAN, derived from the individual rpm sensors on each wheel, when the cruise is set to 'on' by a button push on the steering wheel switch pack (which does have a resistive ladder), the current speed value from the ABS is stored as the target speed in the ECM, subsequent pushes of the speed + or speed - buttons will increase or decrease the target speed value in the ECM when the corresponding control voltage is received.
 
Graculus said:
It's no different to any other input from a sensor - boost pressure or suspension height for example. All the resistive ladder does is send a specific voltage input to the ECM, which corresponds to an expected function, for example 1V=suspend, 2V=resume etc. a boost pressure sensor does exactly the same, 1V=1Bar, 2V=2Bar etc. the only difference is the boost pressure sensor is a variable output, not a set of fixed (within a % tolerance) values.
I think 'dangerous' is a stretch, given that a simple dab on the brakes or pressing the 'suspend' button will cancel the cruise control function.
The speed value doesn't come from or go through a resistive ladder, it's a composite speed signal broadcast by the ABS on HS-CAN, derived from the individual rpm sensors on each wheel, when the cruise is set to 'on' by a button push on the steering wheel switch pack (which does have a resistive ladder), the current speed value from the ABS is stored as the target speed in the ECM, subsequent pushes of the speed + or speed - buttons will increase or decrease the target speed value in the ECM when the corresponding control voltage is received.
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Have it your own way, a resistive ladder is kiddy crude and totally unnecessary for setting and controlling speed, the sort of thing that would have got one of my staff a kicking if such a design had been presented. All is easily done in software with minimal code as I know from experience in controlling speed. It is clearly potentially dangerous if it can cause unintended acceleration.
 
Datatek said:
... It is clearly potentially dangerous if it can cause unintended acceleration.
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Well for one, we don't know it's the steering wheel switch pack at fault - yet. If it is, it's not a common failure because the papers, internet forums or 'social media' are not full of reports about this 'dangerous' system, which IMO is probably safer than lots of relays, vacuum solenoids etc. etc. that other systems seem to employ.
 
Graculus said:
Well for one, we don't know it's the steering wheel switch pack at fault - yet. If it is, it's not a common failure because the papers, internet forums or 'social media' are not full of reports about this 'dangerous' system, which IMO is probably safer than lots of relays, vacuum solenoids etc. etc. that other systems seem to employ.
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No relays needed on electronically controlled engines or vacuum for that matter.
 
I still don't think you've got a grip of how this all works - the resistive ladder is purely in the steering wheel switch pack, for signalling switch activation to the ECM, all other inputs & outputs are either on HS-CAN or directly from the ECM to injectors / actuators. Other than the reference 5V, there is no input to the switches, they're purely an output device.
The only other way it's done in later LR systems is with LIN to the BCM, then broadcast on HS-CAN, or private MS-CAN to the steering column control module, then broadcast on HS-CAN. The reason for putting it directly onto HS-CAN is to allow direct input into adaptive speed control.
 
Graculus said:
I still don't think you've got a grip of how this all works - the resistive ladder is purely in the steering wheel switch pack, for signalling switch activation to the ECM, all other inputs & outputs are either on HS-CAN or directly from the ECM to injectors / actuators. Other than the reference 5V, there is no input to the switches, they're purely an output device.
The only other way it's done in later LR systems is with LIN to the BCM, then broadcast on HS-CAN, or private MS-CAN to the steering column control module, then broadcast on HS-CAN. The reason for putting it directly onto HS-CAN is to allow direct input into adaptive speed control.
Click to expand...
How to make something that is simple very complicated. Pleased I have nothing to do with any of that.
 
Signalling which of between four & six buttons have been pressed across a pair of wires (one of which is a reference voltage) by using voltages derived from a resistive ladder or sending switch states on a LIN is complicated? Every vehicle manufacturer uses one or both for everything including cruise control, window switches, heater controls, interior lighting, electric seat controls etc. etc. - and has done for a period of time extending into the last century.
 
Graculus said:
Signalling which of between four & six buttons have been pressed across a pair of wires (one of which is a reference voltage) by using voltages derived from a resistive ladder or sending switch states on a LIN is complicated? Every vehicle manufacturer uses one or both for everything including cruise control, window switches, heater controls, interior lighting, electric seat controls etc. etc. - and has done for a period of time extending into the last century.
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Easily and reliably done with a chip. Car electronics have become a joke IMO, a fault in one module can cause all manner of non related faults.
 
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