cruise control - Page 2 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



Welcome Enthusiast! If you already own a Chevy TrailBlazer or GMC Envoy or perhaps thinking of purchasing such a vehicle, then you have come to the best TrailBlazer and Envoy site on the net! Rainier, Bravada, Ascender, and 9-7x owners welcome too!

You are currently viewing our site as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to search and post topics, communicate privately with other members, respond to polls, upload content, and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

If you have any problems with the registration process or your account login, please contact contact us.
Join Today!
Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 General Tech Q&A > General

General If it doesn't fit in any other forum

TrailVoy.com is the premier GMC Envoy Forum on the internet. Registered Users do not see the above ads.
Reply
 
Thread Tools
  #11  
Old 08-04-2010, 09:05 AM
Topher's Avatar
Topher Topher is offline
Member
 
2002 GMC Envoy SLT
Light Pewter Metallic 4.2L I6 4X4
Join Date: Oct 2009
Location: Northeast Ohio
Posts: 132
Here is how the cruise works, and what affects it. Pay particular attention to what causes it to disengage.

CRUISE CONTROL DESCRIPTION AND OPERATION

Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at vehicle 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 powertrain control module (PCM)
* The On/Off switch
* The Resume/Accel switch
* The Set/Coast switch
* The torque converter clutch (TCC) brake switch
* The stop lamp switch
* The throttle actuator control (TAC) motor
* The vehicle speed sensor (VSS)

Cruise Control Engaged
The cruise control system will engage and adjust the vehicle speed based on the activation of the following cruise control switches:

* On/Off
* Resume/Accel
* Set/Coast

The cruise control switches are located on the multifunction/turn signal lever.

The powertrain control module (PCM) monitors the signal circuits of the cruise control switches in order to determine when to capture and maintain the selected vehicle speed. The PCM uses the throttle actuator control (TAC) module motor in order to control the vehicle speed. For further information on the TAC system, refer to Throttle Actuator Control (TAC) System Description in Computers and Control Systems - 4.2L.

Ignition positive voltage is supplied from the 10-amp HVAC 1 fuse to the cruise control switch via the ignition 3 voltage circuit. When the normally open cruise control On/Off switch is turned ON, the switch closes and the PCM detects a high signal voltage on the cruise control on switch signal circuit. When the normally open Set/Coast switch is pressed, the switch closes and the PCM detects a high signal voltage on the cruise control set/coast switch signal circuit. To engage the cruise control system, turn the On/Off switch ON and momentarily press the Set/Coast switch. The PCM will confirm that the cruise control enable criteria has been achieved. The PCM will engage the cruise control system and record the selected vehicle speed. The PCM sends a class 2 message to the instrument panel cluster (IPC) in order to illuminate the cruise control indicator. 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/Coast switch and the Resume/Accel switch. When the cruise control system is engaged, pressing and holding the Set/Coast switch will allow the vehicle to decelerate from the current set vehicle speed without deactivating the cruise control system. When the Set/Coast switch is released, the PCM 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/Coast switch will allow the vehicle to decelerate at 1 mph increments for each time that the Set/Coast is momentarily pressed, with a minimum vehicle speed of 23 mph . When the normally open Resume/Accel switch is activated, the switch closes and the PCM detects a high signal voltage on the cruise control resume/accel switch signal circuit. Activating and holding the Resume/Accel 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 Resume/Accel switch is released, the PCM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily activating the Resume/Accel switch will allow the vehicle to accelerate at 1 mph increments for each time that the Resume/Accel switch is momentarily activated, with the maximum acceleration total of 10 mph over the current set vehicle speed. Momentarily activating the Resume/Accel switch, after the cruise control system has been disengaged by pressing the brake pedal, will recall the previous set vehicle speed that is recorded in the PCM.

Cruise Control Disengaged
The powertrain control module (PCM) disengages the cruise control operation based on the signals from the following switches:

* The On/Off switch
* The torque converter clutch (TCC) brake switch
* The stop lamp switch

The TCC brake switch and the stop lamp switch are incorporated into an assembly and are mounted to the brake pedal bracket. Pressing the brake pedal while the cruise control is engaged will disengaged the cruise control system. The PCM monitors the TCC brake switch/cruise control release signal circuit and the stop lamp switch signal circuit. When the brake pedal is pressed, the normally closed TCC brake switch opens and the normally open stop lamp switch closes. The PCM detects a low signal voltage on the TCC brake switch/cruise control release signal circuit and detects a high signal voltage on the stop lamp switch signal circuit. The cruise control system will disengage when the cruise control On/Off switch is turned OFF. The vehicle speed stored in the memory of the PCM will be erased when the cruise control On/Off switch is turned to OFF, or the ignition switch is turned OFF.

The cruise control system will disengage when the PCM detects that the driver has the accelerator pedal override active for approximately 60 seconds.

When the cruise control system is disengaged, the PCM sends a class 2 message to the instrument panel cluster (IPC) in order to deactivate the cruise control indicator.

Cruise Control Inhibited
The powertrain control module (PCM) inhibits the cruise control operation when any of the following conditions exist:

* The PCM detects that the center high mounted stop lamp (CHMSL) is not operating properly.
* A cruise control system related DTC has been set.
* The vehicle speed is less than 40 km/h (25 mph) .
* The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear.
* The engine RPM low.
* The engine RPM is high.
* The vehicle speed is to high.
* The system voltage is not between 6-16 volts .
* The antilock brake system/traction control system (TCS) is active for more than 2 seconds.



So, your cruise could turn off if:
  • Your CHMSL is lighting when it shouldn't.
  • The switch is bad internally, and it's "turning off" when it shouldn't.
__________________
200k miles and counting
Fullly stocked with Amsoil; Quad headlight mod; Jetttstream quad LED brakelights.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #12  
Old 08-04-2010, 07:51 PM
RayVoy's Avatar
RayVoy RayVoy is offline
TrailVoy Guru
 
2009 Chevy Avalanche LTZ
Black 5.3L V8 4X4
Join Date: Jul 2006
Location: Atlantic Canada
Posts: 6,431
Quote:
Originally Posted by Topher View Post


So, your cruise could turn off if:
  • Your CHMSL is lighting when it shouldn't.
  • The switch is bad internally, and it's "turning off" when it shouldn't.
Well, there is nothing unique about the 3rd brake light.
It operates from the same switch contacts as the side brake lights.

However, I agree, if any brake light is operating when it should not, the cruise will dis-engage.

We have said, all along, that a faulty brake pedal switch can cause cruise failure.

However, in all reported occurances, the one common factor is that there was a front wheel hub changed.

BUT NO ABS LIGHT
__________________
Ray
Reply With Quote Quick reply to this message
  #13  
Old 08-04-2010, 08:22 PM
Topher's Avatar
Topher Topher is offline
Member
 
2002 GMC Envoy SLT
Light Pewter Metallic 4.2L I6 4X4
Join Date: Oct 2009
Location: Northeast Ohio
Posts: 132
Quote:
Originally Posted by RayVoy View Post
Well, there is nothing unique about the 3rd brake light.
It operates from the same switch contacts as the side brake lights.

However, I agree, if any brake light is operating when it should not, the cruise will dis-engage.

We have said, all along, that a faulty brake pedal switch can cause cruise failure.

However, in all reported occurances, the one common factor is that there was a front wheel hub changed.

BUT NO ABS LIGHT
Sorry...too specific of a failiure. Since the factory repair manual specifically states the PCM inhibits the cruise control operation when the PCM detects that the center high mounted stop lamp (CHMSL) is not operating properly, I thought it was an interesting note. Not the reason but a reason.

And the front wheel hub change may have to do with the PCM seeing a wheel rotating less than 25mph, thus inhibiting the cruise engagement. I can look more at the wiring diagrams tomorrow at work.
__________________
200k miles and counting
Fullly stocked with Amsoil; Quad headlight mod; Jetttstream quad LED brakelights.
Reply With Quote Quick reply to this message
  #14  
Old 08-04-2010, 09:11 PM
RayVoy's Avatar
RayVoy RayVoy is offline
TrailVoy Guru
 
2009 Chevy Avalanche LTZ
Black 5.3L V8 4X4
Join Date: Jul 2006
Location: Atlantic Canada
Posts: 6,431
Quote:
Originally Posted by Topher View Post
And the front wheel hub change may have to do with the PCM seeing a wheel rotating less than 25mph, thus inhibiting the cruise engagement. I can look more at the wiring diagrams tomorrow at work.
Sorry, the PCM gets its speed info from the VSS (vehicle speed sensor) mounted in the transfer case on 4x4 trucks, or in the tranny tail piece on 2 wd trucks.

The front hubs are only for ABS (and perhaps traction control) speed sensing.

I do not, however, understand what the torque converter clutch has to do with it and/or what connection it has to the brake pedal position switch.

I do think, there may be a connection with the traction control circuits.
But not sure what at this time.
__________________
Ray
Reply With Quote Quick reply to this message
  #15  
Old 08-04-2010, 10:57 PM
Topher's Avatar
Topher Topher is offline
Member
 
2002 GMC Envoy SLT
Light Pewter Metallic 4.2L I6 4X4
Join Date: Oct 2009
Location: Northeast Ohio
Posts: 132
Quote:
Originally Posted by RayVoy View Post
Sorry, the PCM gets its speed info from the VSS (vehicle speed sensor) mounted in the transfer case on 4x4 trucks, or in the tranny tail piece on 2 wd trucks.

The front hubs are only for ABS (and perhaps traction control) speed sensing.

I do not, however, understand what the torque converter clutch has to do with it and/or what connection it has to the brake pedal position switch.

I do think, there may be a connection with the traction control circuits.
But not sure what at this time.
Don't apologize. When you depress the brake pedal, the TCC immediately disengages lockup. My guess is that so that when you accelerate, there is no "down-shift" delay.

I'll investigate the diagrams tomorrow.
__________________
200k miles and counting
Fullly stocked with Amsoil; Quad headlight mod; Jetttstream quad LED brakelights.
Reply With Quote Quick reply to this message
  #16  
Old 08-05-2010, 06:16 PM
RayVoy's Avatar
RayVoy RayVoy is offline
TrailVoy Guru
 
2009 Chevy Avalanche LTZ
Black 5.3L V8 4X4
Join Date: Jul 2006
Location: Atlantic Canada
Posts: 6,431
Quote:
Originally Posted by Topher View Post
Don't apologize. .
I wasn't. I was pointing out, what I perceive as an error in your assumption

Quote:
Originally Posted by Topher View Post
When you depress the brake pedal, the TCC immediately disengages lockup.
The TCC is controlled by the PCM, and only the PCM.

The PCM does receive input from the brake pedal position sensor (brake switch), which it uses to dis-engage the cruise.
It may also use this input to dis-engage the torque converter clutch.

But, it is my belief, that the cruise and the TCC are separate from each other.
__________________
Ray
Reply With Quote Quick reply to this message
  #17  
Old 08-06-2010, 10:33 AM
Topher's Avatar
Topher Topher is offline
Member
 
2002 GMC Envoy SLT
Light Pewter Metallic 4.2L I6 4X4
Join Date: Oct 2009
Location: Northeast Ohio
Posts: 132
Quote:
Originally Posted by Topher View Post
...And the front wheel hub change may have to do with the PCM seeing a wheel rotating less than 25mph...
Quote:
Originally Posted by RayVoy View Post
Sorry, the PCM gets its speed info from the VSS (vehicle speed sensor) mounted in the transfer case on 4x4 trucks, or in the tranny tail piece on 2 wd trucks.
Did you see the word "may" there? It means I wasn't sure (I was simply too busy to think clearly so I figured I'd check it later). And why don't you understand the connection between the TCC circuit and the cruise? It's called redundancy.

Quote:
Originally Posted by RayVoy View Post
I wasn't. I was pointing out, what I perceive as an error in your assumption
Duh.

Quote:
Originally Posted by RayVoy View Post
The TCC is controlled by the PCM, and only the PCM.
Yes, I know. I should have used a longer explanation and said when the brakes are applied, there is a TCC release signal seen by the PCM, which disengages the TCC. I didn't mean to imply the brake switch turned off the TCC directly.

Quote:
Originally Posted by RayVoy View Post
The PCM does receive input from the brake pedal position sensor (brake switch), which it uses to dis-engage the cruise.
It may also use this input to dis-engage the torque converter clutch.

But, it is my belief, that the cruise and the TCC are separate from each other.
Well, sometimes beliefs are wrong. There is no "may" in this case. The PCM gets two distinct and different inputs from the switch assembly. Both the cruise and the TCC use the brake pedal assembly, which has a multipurpose switch built into it (not a position sensor).The whole reason I posted the circuit operation is so that everyone could read how cruise works. If you don't want to read it okay, here is the one section in question you skipped: "The PCM monitors the TCC brake switch/cruise control release signal circuit and the stop lamp switch signal circuit. When the brake pedal is pressed, the normally closed TCC brake switch opens and the normally open stop lamp switch closes. The PCM detects a low signal voltage on the TCC brake switch/cruise control release signal circuit and detects a high signal voltage on the stop lamp switch signal circuit.". So, the PCM does watch the TCC circuit as well as the brake circuit to control cruise. Having both means if one goes bad, it can see the other and still turn off the cruise.

Heck, it's even part of the connector diagram (Pin C below):

Oh, and
Attached Images
 
__________________
200k miles and counting
Fullly stocked with Amsoil; Quad headlight mod; Jetttstream quad LED brakelights.
Reply With Quote Quick reply to this message
  #18  
Old 08-06-2010, 08:54 PM
RayVoy's Avatar
RayVoy RayVoy is offline
TrailVoy Guru
 
2009 Chevy Avalanche LTZ
Black 5.3L V8 4X4
Join Date: Jul 2006
Location: Atlantic Canada
Posts: 6,431
Chill pal, I'm not looking for a fight, just trying to fix this poor SOB's cruise control problem.

We are talking about the same thing.
When I said that the PCM receives a signal from the brake pedal switch, I'm talking about pin c, the purple wire.

The PCM can do a number of things with this signal.
It turns off the cruise control
It also unlocks the the TCC.

These are two separate circuits, simply triggered by the same input.

One does not impact the other; however, failure of the common input will fail both.

I simply maintain, that it is confusing to reference one when we should be talking about the other.


I'm sure, that if we (two knowledgeable people) work together, we can solve this problem that now appears to be affecting a number of members.
__________________
Ray
Reply With Quote Quick reply to this message
  #19  
Old 08-06-2010, 10:18 PM
dondude dondude is offline
Junior Member
 
2002 GMC Envoy SLT
Pewter Metallic 4.2L I6 4X4
Join Date: Mar 2009
Location: Cottrellville, MI
Posts: 39
When i was having misfire problems my cruise wouldn't engage. Cruise control must have a lot of safety switches to hurdle. Who ever knew it was so advanced?
Reply With Quote Quick reply to this message
  #20  
Old 09-12-2010, 03:27 PM
RayVoy's Avatar
RayVoy RayVoy is offline
TrailVoy Guru
 
2009 Chevy Avalanche LTZ
Black 5.3L V8 4X4
Join Date: Jul 2006
Location: Atlantic Canada
Posts: 6,431
This thread appears to have the answer

http://forums.trailvoy.com/showthread.php?t=78414
__________________
Ray
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum forums, you must first register.

Please enter your desired user name, your email address and other required details in the form below.
(Only letters, numbers, dashes and underscores are permitted for user names)
The user name that you choose is permanent and can never be changed.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


» Sponsors

Advertising Info

All times are GMT -4. The time now is 09:48 AM.


Chevy TrailBlazer and GMC Envoy Enthusiasts - Copyright 2004 - 2009 All Rights Reserved.
All trademarks referenced herein are property of their respective owners.
RSS Feed