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​Cruise control, high idle and Jakes - What your DDEC III or DDEC IV requires before it activates these functions.

By Fernando DeMoura

December, 2019

Almost all DDEC III and DDEC IV ECMs have the hardware to support high idle, cruise control, and engine brake (Jake) functions and most DDEC III and DDEC IV ecms set up for highway applications already have these functions programmed in. If your DDEC isn’t activating one or more of these functions the below tables might be helpful. Engine protection systems such as high coolant, oil, or intake manifold temperature, and low coolant level and low oil pressure can disable these three functions depending on how you have your engine protection settings programmed.

Jakes

The Jakes can come on just under the RPM limiter and stay on all the way down to 851 rpm. 

The minimum activation mph can be programmed to 0 and there is no limit on the maximum vehicle speed

Engine protection - Warning

Will not disable any Jake functions

Engine protection - Derate

Will not disable any Jake functions

Engine protection - Shutdown

Will not disable any Jake functions

Medium Jake request (pin K2)

Supplying a ground enables the Jake brake for Cylinders 3, 4, 5, and 6

Low Jake request (pin K3)

Supplying a ground enables the Jake brake for Cylinders 1 and 2

Park Brake (pin H2 on the ECM)

Has no effect on Jake functions

Service Brake (pin G2 on the ECM)

Has no effect unless Jakes are programmed to only come on with service brake

Throttle

Any application of the throttle will disable the Jakes

Clutch (pin J2 on the ECM)

Jake functions can’t activate unless a ground is supplied to pin J2

Jake disable - Freightliners (Pin E1)

Disables the Jakes on some freightliners if a ground is supplied

Cruise control.

Cruise usually becomes available at 20 mph and 1000 rpm and cuts off at 85 mph and 2110 rpm but I’ve programmed it to come on as low as 10 mph and 600 rpm and as high as 125 mph and 2800 rpm. 

Engine protection - Warning

Will not disable cruise

Engine protection - Derate

Will disable cruise until temperature comes down

Engine protection - Shutdown

Will disable cruise until the engine is completely shut down.

Cruise enable (pin F2)

Cruise will not activate unless a ground is supplied to pin F2

Cruise set (pin J1)

Supplying a ground sets the current vehicle speed as the set cruise speed

Cruise accelerate (pin G3)

Supplying a ground raises the desired cruise speed

Park Brake (pin H2 on the ECM)

Supplying a ground will disable the cruise function

Service Brake (pin G2 on the ECM)

Cruise will not activate unless a ground is supplied to pin G2

Throttle

The throttle is functional and will not disable cruise.

Clutch (pin J2 on the ECM)

Cruise will not activate unless a ground is supplied to pin J2

High idle

High idle will only activate below 3 mph. 

Engine protection - Warning

Will not disable high idle

Engine protection - Derate

Will not disable high idle

Engine protection - Shutdown

Will disable high idle until the engine is completely shut down.

Cruise enable (pin F2)

High idle will not activate unless a ground is supplied to pin F2

Cruise set (pin J1)

Supplying a ground goes to min high idle rpm and also lowers desired high idle rpm

Cruise accelerate (pin G3)

Supplying a ground raises desired high idle rpm

Park Brake (pin H2 on the ECM)

High idle will not activate unless a ground is supplied to pin H2

Service Brake (pin G2 on the ECM)

Has no effect on high idle functions

Throttle

The throttle is functional and will not disable high idle or change high idle desired rpm

Clutch (pin J2 on the ECM)

Has no effect on high idle functions

Written by Fernando DeMoura, Diesel Control Service. Phone 412-327-9400 - www.dieselcontrolservice.com