Cruise Control Intermittent - Chevy and GMC Duramax Diesel Forum
07.5-10 LMM Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

 
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post #1 of 8 (permalink) Old 04-04-2019, 11:26 AM Thread Starter
 
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Cruise Control Intermittent

Cruise functions normally except it disengages every 5-15 min.
I've got a China Tech2Win that shows no codes for cruise, current or history. I have no current codes from any modules. I had a recent P2269, water in fuel, and replaced the water-in-fuel sensor to fix it--found no water in filter after draining filter 3 times.

I've replaced the stop lamp switch, AC Delco, and spent some time looking for wiring/connector problems. I found the transmission wiring above the transmission had crumbled loom and replaced the loom but found no rubbed through wire, specifically with the L-BLU/W wire from the stop lamp switch.
Any thoughts on specifically where to look for wiring problems/grounds?

My Tech2Win monitors data from cruise control including the last 8 cruise disengagements. On a test drive it shows "brake" on brake application and "cancel" when I depress the cancel button, the uncommanded disengage is "pedal initialize". I have no idea what this means and can't find it in AllData.

Any input would be appreciated.

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'09 GMC LMM CCLB 4x4, 165k miles, DPF Pipe, Ridge Runner Tunes, AFE Oiled Gauze Air Filter (10-10101)

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post #2 of 8 (permalink) Old 11-18-2019, 11:13 PM
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Mine did the same thing! Ended up being a brake switch. Wash fix for mine. Hope that helps


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post #3 of 8 (permalink) Old 11-19-2019, 03:37 AM
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Mine did the same. Change the brake light switch (it is what triggers the cut off, just as if you stepped on the brake pedal). It is located at the top of the arm on the brake pedal.

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2008 Silverado 2500HD CCSB LTZ Diesel
FASS 95 Lift Pump (with Baldwin filters), Edge Insight CTS Monitor on a Windshield Mount, Nicktane Fuel Filter Adapter w/ CAT 306-9199 UHE tertiary fuel filter, Bilstein 5100 Stock Height, Bushwacker Bed Rail Caps, AMP Research Bedstep, Fumoto oil drain valve, Dorman PS Oil cooler, Pioneer AVIC 7200NEX GPS/Stereo, Air Lift LoadLifter 5000 Air Bags.

Last edited by 407driver; 11-19-2019 at 03:42 AM.
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post #4 of 8 (permalink) Old 11-19-2019, 10:58 AM Thread Starter
 
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I've replaced the brake light switch.

"wine is a constant proof that God loves us, and loves to see us happy" Ben Franklin
"Only the dead have seen the end of war" Plato


'09 GMC LMM CCLB 4x4, 165k miles, DPF Pipe, Ridge Runner Tunes, AFE Oiled Gauze Air Filter (10-10101)

'05 LLY Sold
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post #5 of 8 (permalink) Old 11-19-2019, 11:25 AM
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Quote:
Originally Posted by shadow02 View Post
I've replaced the brake light switch.
Well, drive around for a while over some rough roads and see what happens. Mine always kicked off when I hit a bump in the road.

2008 Silverado 2500HD CCSB LTZ Diesel
FASS 95 Lift Pump (with Baldwin filters), Edge Insight CTS Monitor on a Windshield Mount, Nicktane Fuel Filter Adapter w/ CAT 306-9199 UHE tertiary fuel filter, Bilstein 5100 Stock Height, Bushwacker Bed Rail Caps, AMP Research Bedstep, Fumoto oil drain valve, Dorman PS Oil cooler, Pioneer AVIC 7200NEX GPS/Stereo, Air Lift LoadLifter 5000 Air Bags.
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post #6 of 8 (permalink) Old 11-19-2019, 11:33 AM
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Quote:
Originally Posted by shadow02 View Post
I've replaced the brake light switch.
you could also have a bad brake bulb or a bad ground in the brake light. This can cause some current to flow through the brake circuit from the parking light circuit and can occasionally cause the vehicle to detect the brake is pressed even when the switch if working and the brake is not pressed. I have seen this a few dozen times in my time working on cars and trucks, so its not an every day issue, but its common enough where its worth checking. If the truck detects voltage on the brake wire (what happens when you press the brake pedal) it will disengage cruise control. It does not take a full 12 volts to do this, ive seen it trip cruise control around 1V or so on some vehicle.s

2015 Chevy Silverado 2500 HD 6.6L LML
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post #7 of 8 (permalink) Old 11-20-2019, 09:01 AM Thread Starter
 
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Yep, but my tech 2 shows "brake initialize" as the reason for the uncommanded disengage, If I apply the brake the tech 2 shows "brake applied. I've driven around a lot with the tech 2 connected and always see the same reason for the uncommanded disengage.

I've read that "brake initialize" is the first application of the brake on start and is sent from the BCM to the ECM. So I don't understand "brake initialize" coming up as I'm cruising along. Maybe the problem's in my Roadrunner stuff. I've not changed the ECM to see.

"wine is a constant proof that God loves us, and loves to see us happy" Ben Franklin
"Only the dead have seen the end of war" Plato


'09 GMC LMM CCLB 4x4, 165k miles, DPF Pipe, Ridge Runner Tunes, AFE Oiled Gauze Air Filter (10-10101)

'05 LLY Sold
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post #8 of 8 (permalink) Old 11-20-2019, 05:21 PM
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Maybe something here will be of interest to you. I note that the GMLAN is involved and anything on that circuit could cause problems.





Cruise Control Description and Operation

Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at speeds above 40 km/h (25 mph). Steep grades may cause variations in the selected vehicle speeds.

The following are the main components of the Cruise Control System:


  • The accelerator pedal
  • The stop lamp switch
  • The body control module (BCM)
  • The cruise control switches
  • The engine control module (ECM)
  • The throttle actuator control (TAC) motor
  • The vehicle speed sensor (VSS)
Cruise Control Engaged

The Cruise Control System will engage and adjust vehicle speeds, based on the activation of the following cruise control switches, which are located on the steering wheel:


  • The on/off switch
  • The + RES switch
  • The - SET switch
The body control module (BCM) monitors the signal circuit of the cruise control switches. The BCM relays the cruise control switch status to the engine control module (ECM) via the GMLAN serial data circuit. The ECM uses the status of the cruise control switch to determine when to capture and maintain the vehicle speed. The ECM monitors the vehicle speed signal circuit in order to determine the desired vehicle speed. The ECM uses the throttle actuator control (TAC) motor in order to maintain the vehicle speed. For further information on the TAC System, refer to Throttle Actuator Control (TAC) System Description for the 4.3L engine or Throttle Actuator Control (TAC) System Description for the 4.8L, 5.3L, 6.0L, 6.2L or 7.0L engines.

Voltage is supplied to the cruise control switch via the steering wheel control switch reference voltage circuit supplied by the BCM. The cruise control function switches are arranged in a resistive ladder design, with each cruise control function switch having a different resistance value. The BCM detects a specific voltage value that is associated with the cruise control function switch being activated. When the normally open cruise control on/off switch is turned ON, the switch closes and the BCM supplies a ground to the cruise control switch ON indicator circuit as it becomes illuminated. The BCM sends a GMLAN serial data message to the ECM indicating that the on/off switch is active. Similarly, when the normally open + RES switch or the normally open - SET switch are pressed, the switch closes and the BCM detects the predetermined voltage signal on the cruise control set/coast and resume/accel switch signal circuit. The BCM sends a GMLAN serial data message to the ECM indicating that the + RES switch or the - SET switch is active. To engage the Cruise Control System, ensure that the vehicle speed is above 40.2 km/h (25 mph), turn the cruise On/Off switch ON and momentarily press the - SET switch. The ECM will engage the Cruise Control System and record the vehicle speed. The ECM sends a GMLAN serial data message to the driver information center (DIC) in order to illuminate the CRUISE SET TO ### message. The ECM sends a GMLAN serial data message to the instrument panel cluster (IPC) in order to illuminate the Cruise Engaged indicator in the IPC. The - SET switch and the + RES switch will remain inactive when the BCM has not received the predetermined voltage signal from the on/off switch. Pressing the accelerator pedal, while the Cruise Control System is engaged, will allow the driver to override the Cruise Control System in order to accelerate the vehicle beyond the current set vehicle speed. When the accelerator pedal is released, the vehicle will decelerate and resume the current set vehicle speed. The driver can also override the current set vehicle speed via the - SET switch and the + RES switch. When the Cruise Control System is engaged, pressing and holding the - SET switch will allow the vehicle to decelerate from the current set vehicle speed without deactivating the Cruise Control System. When the - SET switch is released, the ECM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the Cruise Control System is engaged, momentarily pressing the - SET switch will allow the vehicle to decelerate at 1.6 km/h (1 mph) increments for each time that the - SET is momentarily pressed, with a minimum vehicle speed of 37 km/h (23 mph). Pressing and holding the + RES switch, when the Cruise Control System is engaged, will allow the vehicle to accelerate to a greater vehicle speed than the current set vehicle speed. When the + RES switch is released, the ECM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the Cruise Control System is engaged, momentarily pressing the + RES switch will allow the vehicle to accelerate at 1.6 km/h (1 mph) increments for each time that the + RES switch is momentarily pressed, with the maximum acceleration total of 16 km/h (10 mph) over the current set vehicle speed. Momentarily activating the + RES switch will recall the previous vehicle speed, after the cruise control system is disengaged by pressing the brake pedal or by activating the CANCEL switch.

Cruise Control Disengaged

The engine control module (ECM) disengages the cruise control operation based on the signals from the following switches:


  • The stop lamp switch
  • The cruise control On/Off switch
  • The cruise control cancel switch
The body control module (BCM) determines when the cruise control cancel switch is activated. When the normally open cancel switch is closed, the BCM detects the predetermined voltage signal on the cruise control function switch circuit. The BCM sends a GMLAN serial data message to the ECM in order to disengage the cruise control system.

The stop lamp switch is mounted on the brake pedal bracket. When the brake pedal is applied, the normally open stop lamp switch closes. The ECM monitors the stop lamp signal circuit through a discrete input and a GMLAN serial data message signal from the BCM indicating the brake status. When both signals indicate the brake pedal is applied, the ECM will disengage the cruise control system.

The Cruise Control System will disengage when the cruise control on/off switch is switched OFF. The vehicle speed stored in the memory of the engine control module will be erased when the cruise control On/Off switch is turned OFF, or the ignition switch is turned OFF.

The Cruise Control System will disengage when the ECM detects that a driver override function has been active for approximately 60 seconds. When the Cruise Control System has been disengaged, the ECM sends a GMLAN serial message to the instrument panel cluster (IPC) in order to turn OFF the Cruise Engaged indicator, and to the driver information center (DIC) in order to turn OFF the CRUISE SET TO ### message.

Each time the Cruise Control System is disengaged, the ECM will keep track of the reason for system disengagement. The last 8 disengagement reasons will be recorded within the ECM memory, and can be viewed with a scan tool.

Cruise Control Inhibited

The engine control module (ECM) inhibits the cruise control operation when any of the following conditions exist:


  • The ECM has not detected a brake pedal activation from the body control module (BCM).
  • A Cruise Control System DTC has been set.
  • The vehicle speed is less than 40.2 km/h (25 mph).
  • The vehicle speed is too high.
  • The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear.
  • The engine RPM is too low.
  • The engine RPM is too high.
  • The system voltage is not between 9-16 volts.
  • The Antilock Brake System (ABS)/Traction Control System (TCS) is active for more than 2 second

Ron Nielson
2008 Silverado LT, CCLB, Edge Insight CTS
2009 Arctic Fox 29-5T, Silver Fox Edition, Onan 3600 LPG generator
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