Traction Control versus Cruise Control Question:

We often spotlight down a long section of dirt road out at the property and set cruise control on the minimum speed setting.

Did this in the D2 and do it regularly in the D4.

I have seen the traction control come on doing this,particularly if there has been recent rain,and there are muddy sections on the road,which are black clay.

I have also used it at low speed looking for a good gutter while driving on the beach,but can't remember seeing TC coming on doing this.

Just a couple of examples where CC is not used at high speeds.

Quote:

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Originally Posted by sierrafery

Describe what happened maybe it has some logic... there is the so called VSS(vehicle speed signal)a digital signal which is used by both CC and TC systems and it's generated by the SLABS ECU calculated based on all 4 ABS sensor inputs, there are cases when this signal has a momentary failure which would cancel the CC and affect the TC operation too... usually you'll find a "road speed missing" fault code logged in the engine ECU if it's that.

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This has not happened to me. I am just curious. I think that the TC will not activate at speed, I find it hard to think of to be in a situation, driving at speed to cause the traction control to kick in. Something happens that at 100 kph one wheel slip so much that the traction control kicks in is going to be a very bad situation any way.

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Originally Posted by Bohica

This has not happened to me. I am just curious. I think that the TC will not activate at speed, I find it hard to think of to be in a situation, driving at speed to cause the traction control to kick in. Something happens that at 100 kph one wheel slip so much that the traction control kicks in is going to be a very bad situation any way.

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I vaguely remember traction control kicking in,on occasions, at speed on dirt roads with bad corrugations.

That is at speeds over 80 km/hr.

Only happened in the D2,never seen it happen in the D4.

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Originally Posted by Pedro_The_Swift

Do people actually operate cruise control anywhere other than a highway???
how on earth does TC cut in at 100kph?
The two systems should never "meet" surely,,,

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I would love it if my CC would work at a speed that let me crawl over rocks etc. My old G60 Patrol had a hand throttle. So did all the Military LRs I worked with and on. It is brilliant when the going is rough and a bit bouncy, and your foot is likely to bob up and down on the loud pedal. Cruise would be amazing in that situation.

Often I used to use the CC control on the Scania to hold revs to build up air over the trailers. Maybe something similar is poss on LRs. Not likely, I know, but my point is that CC isn't only for 100 Km/h on the freeway,

You can indeed...but the threshold is massively higher.
tures down to the wear bars it doesn't take much water on the road to get planing...

I've seen TC operate briefly on the highway in heavy rain in the Defender.

The systems are inter link and Tc will turn CC off . As tc will need to pull back engine power and possibly add braking to wheels .

IMO according to the system's descriptions the CC is disabled by a brake switch input which is not the case when TC kicks in, if it does and affects the vehicle speed normally the CC should work to keep the speed steady like when you meet a hill with CC on not to be disabled

CC will also drop if there is a sudden change in speed, up or down and an event that would activate TC at speed would also cause a jump in the speed reading therefore drop CC.

why? isnt the CC's job to keep the vehicle's speed steady especially where there are speed variations?

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Originally Posted by DESCRIPTION AND OPERATION 18-1-41

Cruise control
All markets have a common cruise control system. The cruise control system, when activated, regulates vehicle
speed. The ECM controls the cruise control system.

Cruise control activation
Cruise control is a passive system, and must be activated by the driver. Cruise control is activated by switching on
the cruise control master switch located on the instrument panel. A LED in the switch illuminates indicating cruise
control is available. The driver must accelerate the vehicle to the desired speed using the accelerator pedal. When
the desired speed is reached, cruise control can be activated by pressing the SET+ switch.

Cruise control will only activate if the following conditions are met:
l Vehicle speed is above 22 mph (35 km/h).
l The brake pedal is not pressed.
l The clutch pedal is not pressed (manual transmission only).
l The transmission is not in Park, Reverse or Neutral (automatic transmission only).

The ECM receives the set signal and determines the vehicle speed provided by the SLABS ECU. The ECM then
maintains current road speed.

Cruise control cancellation
Cancelling cruise control enables the driver to regain control of the vehicle speed by using the accelerator pedal.
Cruise control is cancelled if any of the following conditions occur:
l The brake pedal is pressed.
l The RES switch is pressed.
l The clutch pedal is pressed (manual transmission only).
l The cruise control master switch is switched off.
l The transmission is placed in Park, Neutral, or Reverse (automatic transmission only).
The ECM cancels cruise control operation and returns it to the control of the accelerator pedal.
The set speed will be stored in the ECM unless:
l The cruise control master switch is switched off.
l The ignition is switched off.
If cruise control is deactivated using either of the above methods, the set speed will be erased from the memory of
the ECM.

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