Cruise control mind of its own

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Datsun770

Member
Posts
47
Hello again all

How are we all this fine easter Sunday?

Another gremlin with the 2011 RRS TDV6 auto.

Set the cruise control to a set speed but regardless of the set speed it continues to accelerate beyond and continues until you hit the brake pedal or cancel the cruise using the button. They work fine.

I am.about to attempt a drive from West of Scotland to Norfolk as my brother has passed away and I need to take care if his last officer etc and ideally hoping there is a quick driveway fix for this one of you have unearthed having encountered this issue?

The resume button works the set button works but the speed is not remaining at set speed. No warning lights or anything.

Wheel speed sensor? Steering angle sensor?

Just replaced the brake light switch and that hasn't helped.

Cheers dudes and dudettes.
 
Last edited:
I have never trusted cruise control since I experienced a 'surge' when travelling up the M1 in my old Jag, scared the bejesus out of me because it did n't respond to braking or adjusting from control unit, turned out to be a faulty relay, but put me off them for life and probably scared the pants off the guy driving the AUDI in the fast lane in front of me that I suddenly approached at 'AUDI' driver speed!
As Data siad , full diagnosis is the best option, you don't want to get caught out with a 3 ton beast at full chaff!
 
The cruise control is a relatively basic function, there's a resistive ladder in the switch pack that sends a specific voltage to the ECM - which has the CC supervisory function on HS-CAN.
The first step is to look at live values from the switches - particularly the '+' switch. My guess is that someone has spilt something sticky into the switch pack and it isn't fully releasing, causing the set speed to keep incrementing.
Of course, none of this will set a DTC because the switch pack and the ECM are just responding correctly to driver input....
 
Graculus said:
The cruise control is a relatively basic function, there's a resistive ladder in the switch pack that sends a specific voltage to the ECM - which has the CC supervisory function on HS-CAN.
The first step is to look at live values from the switches - particularly the '+' switch. My guess is that someone has spilt something sticky into the switch pack and it isn't fully releasing, causing the set speed to keep incrementing.
Of course, none of this will set a DTC because the switch pack and the ECM are just responding correctly to driver input....
Click to expand...
Doesn't seem sticky but I noticed the '-' button doesn't slow it down. It just races away past the speed limit. I figured if it was sticking it woukd set itself also. But doesn't. I'll get a look at the live values. What's the best and most accurate way of doing this?

Thanks all for the response so far.
 
There are no relays on a L319 CC system, the inputs are direct voltage from the switchpack, brake pedal & composite speed signal from the ABS, broadcast on HS-CAN and transmission temperature (as an inhibit), again, on HS-CAN. It's a pretty simple system.
 
Easy when you know how. That's another language to me 🤣 any help on ways of diagnosing for dummys appreciated dude. 👍
 
Graculus said:
The cruise control is a relatively basic function, there's a resistive ladder in the switch pack that sends a specific voltage to the ECM - which has the CC supervisory function on HS-CAN.
The first step is to look at live values from the switches - particularly the '+' switch. My guess is that someone has spilt something sticky into the switch pack and it isn't fully releasing, causing the set speed to keep incrementing.
Of course, none of this will set a DTC because the switch pack and the ECM are just responding correctly to driver input....
Click to expand...
A resistive ladder? How crude is that :rolleyes:
 
Datatek said:
A resistive ladder? How crude is that :rolleyes:
Click to expand...
Easy way for the ECU to figure out what switch is being pressed & save wiring, but I agree it's a bit crude & prone to error.

Seemy silly to me to save wires & connector cost, considering all the excessive ECU's in there !!
 
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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