Cruise control issues???

[hellrazer]

First let me introduce myself my name is Jason and few months ago my wife purchased a used 2005 trailblazer ext ls. I love the truck but i am confused by the cruise control. It will engage but it wont hold for long, the longest has been about ten minutes then it shuts off. Most time it is much shorter. I dont know much about this thing so i am asking for a more experienced take on this situation. Thanks in advance for your help.....

Jason

 

[Irishboy02]

First off, welcome! I actually used to go to PennState Berks so I know right where your at. Are there any modifications done to your vehicle, specifically LED lighting? I'v heard rumors (unconfirmed) with the TB and have seen it on the fullsizes that if there is an LED bulb in the brake/running light on the driverside taillight it will cause similar issues with the cruise control. I have absolutely no clue why, something with not enough resistance across the blah blah etc, but thats the best I got for you buddy

 

[DDonnie]

First off, welcome! I actually used to go to PennState Berks so I know right where your at. Are there any modifications done to your vehicle, specifically LED lighting? I'v heard rumors (unconfirmed) with the TB and have seen it on the fullsizes that if there is an LED bulb in the brake/running light on the driverside taillight it will cause similar issues with the cruise control. I have absolutely no clue why, something with not enough resistance across the blah blah etc, but thats the best I got for you buddy

This is the first thing i thought of as well.

 

[hellrazer]

As of what i can see from looking the truck over there is nothing done to it as far as lighting is concerned. The only modifications so far are an aftermarket head unit and an aftermarket drop down dvd player which were done by the dealer to replace the stock units that both had issues. Thanks again for the help...
Jason

 

[Sparky]

I know some people had that problem when a wheel hub bearing was starting to go, and/or was a cheapo replacement that had a sketchy sensor. The cruise is sensitive to speed inconsistencies (for safety reasons to avoid hydroplaning probably) so that could be a possibility for you also. Not sure how the best way would be to track that down is the only thing.

 

[Wooluf1952]

Welcome


In case you haven't heard:
http://gmtnation.com/forums/topic/218-welcome-to-gmtnationcom-heres-the-story/



There are many reasons for the CC to stop working. Is there a CEL ON? I had problems with an intermittent P0300 (random misfire). Never set a CEL, but I found it when I checked with a code reader.

 

[The_Roadie]

I think the most common cause is a hair trigger brake light switch. Have somebody stand behind the vehicle while you manipulate the pedal by hand. Brake lights work even with the ignition switch off.

 

[hellrazer]

Well after a weekend of rolling around under the SHO doing the exhaust for inspection I checked the lights and brake switch in the trailblazer and I found nothing outside the ordinary. The switch takes some effort to activate and holding up the pedal whle driving does nothing for the problem it will still cut out. All the lights are good as well with no led bulbs installed any where in the back. Thanks again for all your help,
Jason

 

[The_Roadie]

There is a special piece of PCM memory that retains the last 5 or 6 reasons that CC clicks off. It's there specifically because troubleshooting this sort of issue is so hard. Problem is only the dealer's TECH II tool can access this memory, and tell you why it turns off. If it's not the brake light switch or a CEL code, my next best guess (if you're trying to avoid paying a non-guaranteed diagnostic charge to the dealer) is dirty contacts in the multifunction switch that turns it on and off. Clean those contacts with electrical contact spray cleaner and see if it gets better.

 

[MAY03LT]

There is a special piece of PCM memory that retains the last 5 or 6 reasons that CC clicks off. It's there specifically because troubleshooting this sort of issue is so hard. Problem is only the dealer's TECH II tool can access this memory, and tell you why it turns off.

Here's a cruise disengage history pic from a TB with an intermittent cruise cutout. You can see events 7 and 8 were from the brake switch (normal), events 5 and 6 were from a DTC, then events 1 through 4 were back to the brake switch. Just like Wooluf's, this TB did not have a check engine light on, however, it had a P0340 stored from a failing cam position sensor. This is why it's worth getting a scan (preferably for free at autozone or wherever) to rule out DTCs as the cause.

 

[The_Roadie]

People who own a personal Tech II tool inhabit a special place in my very small "I'm jealous of your ass" bin.

 

[budwich]

As suggested, it appears that your best bet is a dealer scan... BUT to give you an idea of some of the things that might cause a "shut down", here is the LONG list.... it might help in your "hunt" especially if you can reproduce any of the conditions and / or it gives you an idea of some of the conditions that may trigger things. Of course, a lot can be ruled out for your scenario so its not as bad as it looks. Good luck. My "inexperienced" guess is its your control buttons / wiring (ie chaffed wire touching a ground in the column area) associated there with.

One of the following conditions must be present in order for a disengagement parameter to appear:

• The cruise control system is active and disengagement is requested.

• The engagement of the cruise control system is requested while a fault is present.

Accel Rate: The powertrain control module (PCM)/engine control module (ECM) detects that the vehicle acceleration is greater than the calibrated cruise control threshold.

Bad Sequence: The PCM/ECM detects that a cruise control software execution error is present.

Brake: The PCM/ECM detects that the stop lamps have been activated or the PCM/ECM detects that a stop lamp pedal activation had not occurred before the cruise control system was requested.

Cancel: The PCM/ECM detects that the cruise control cancel switch has been activated.

CC Sw. Position: The PCM/ECM detects that the acceleration mode is active without the activation of the Accel. switch.

Clutch: The PCM/ECM detects that the clutch pedal switch has been activated.

Clutch Switch: The PCM/ECM detects that the clutch pedal switch has been activated.

Cruise Off: The PCM/ECM detects that the cruise On/Off switch was turned to OFF when the cruise control system was enabled.

Coast Low Speed: The PCM/ECM detects that the Set/Coast switch is activated until the vehicle speed is below 37 km/h (23 mph).

Coast Disengage: When the PCM/ECM detects that the cruise set/coast signal is active and the throttle blade fully closes the cruise control system will disengage until the PCM/ECM detects that the set/coast signal is inactive. The cruise control system will then engage and set with the new vehicle speed.

Decel Rate: The PCM/ECM detects that the vehicle deceleration is greater than the calibrated cruise control threshold.

DTC Set: The PCM/ECM detects that a DTC has been set which affects the cruise control operation.

Engine Run Time: The PCM/ECM detects that the cruise control system has been requested and the engine run time counter is not active.

Engine Speed: The PCM/ECM detects that the engine speed is less than or greater than a calibrated RPM.

ETC: The PCM/ECM detects a fault within the throttle actuator control (TAC) system.

First Gear: While the cruise control system is active, the PCM/ECM detects that the transmission is in Drive 1.

High Accel.: The PCM/ECM detects that the vehicle acceleration is greater than the calibrated cruise control threshold.

High Decel.: The PCM/ECM detects that the vehicle deceleration is greater than the calibrated cruise control threshold.

High Speed: The PCM/ECM detects that the vehicle speed is greater than the calibrated amount.

Illegal Mode: The PCM/ECM detects that the acceleration mode is active without the activation of the Accel. switch.

Injector Disable: The PCM/ECM detects that the engine is overspeed and that the fuel shutoff has been activated.

Low Speed: The PCM/ECM detects that the vehicle speed is less than 37 km/h (23 mph) while the cruise control system was enabled.

Low Voltage: The PCM/ECM detects that the ignition voltage is below 9 volts.

Manual/Neutral: The PCM/ECM detects that transmission is in Neutral, Reverse or Park.

Memory Corrupt: An internal PCM/ECM memory fault is detected.

MPH Limit: The PCM/ECM detects a that the vehicle is overspeed and that the fuel shutoff has been activated.

No History: This parameter is displayed when a new PCM/ECM has been installed.

None: This parameter is displayed when a new PCM/ECM has been installed.

Off: The PCM/ECM detects that the cruise On/Off switch was turned to OFF when the cruise control system was enabled.

Over Set Speed: This parameter is displayed when the current vehicle speed is greater than the set vehicle speed by more than a calibrated amount.

Over Speed: This parameter is displayed when the current vehicle speed is greater than the set vehicle speed by more than a calibrated amount.

Over Speed Tap: This parameter is displayed when the Set/Coast switch is briefly applied while the current vehicle speed is greater than the set vehicle speed by more than a calibrated amount.

Pedal Initialize: The PCM/ECM detects that a stop lamp pedal activation had not occurred before the cruise control system was requested.

PCM Error: The PCM/ECM detects that a cruise control software execution error is present.

PCM Inhibit: The PCM/ECM detects a RAM corruption associated to the cruise control system.

Pedal > Cruise: The PCM/ECM detects that the accelerator pedal overrides the set vehicle speed for approximately 60 seconds.

Serial Data: A fault in the serial data circuit from the cruise control switch to the platform module is detected.

S/C On, CC Off: When the PCM/ECM detects that the cruise set/coast signal is active and the throttle blade fully closes the cruise control system will disengage until the PCM/ECM detects that the set/coast signal is inactive. The cruise control system will then engage and set with the new vehicle speed.

S/C On - Speed High: This parameter is displayed when the Set/Coast switch is briefly applied while the current vehicle speed is greater than the set vehicle speed by more than a calibrated amount.

Stop Lamp Switch: The PCM/ECM detects that the stop lamps have been activated.

TAC Inhibit: The PCM/ECM detects a fault within the TAC system.

Traction: The PCM/ECM detects that the traction control system had been activated. It is also possible that a tire with low air pressure can also set this disengagement reason.

Traction Loss: The PCM/ECM detects that the traction control system had been activated. It is also possible that a tire with low air pressure can also set this disengagement reason.

Two Commands: The PCM/ECM detects that the Set/Coast switch and the Resume/Accel switch are active at the same time.

Two CC Commands: The PCM/ECM detects that the Set/Coast switch and the Resume/Accel switch are active at the same time.

Under Speed: The PCM/ECM detects that the vehicle speed is less than the cruise memory speed by more than a calibrated amount.

Under Set Speed: The PCM/ECM detects that the vehicle speed is less than the cruise memory speed by more than a calibrated amount.

 

[hellrazer]

Well thank you all for that info i will grab my buddies scanner tommorow and check for codes but as of a week ago the only code we have gotten out of t is the temperature below threshold and since cleared has never returned. Again thanks for your help i will check for codes and if nothing ther ill be calling the dealer to see what the want to scan it. Thanks again,
Jason

 

[sawicksted]

Well thank you all for that info i will grab my buddies scanner tommorow and check for codes but as of a week ago the only code we have gotten out of t is the temperature below threshold and since cleared has never returned. Again thanks for your help i will check for codes and if nothing ther ill be calling the dealer to see what the want to scan it. Thanks again,
Jason

I had the same problem a while ago....same code issue...plus some other things.... cleaned and played around with the VSS on the transfer case. Re wrapped the wiring and etc...problem went away. Cruise works fine now..

Just drove over 2500miles this week and cruise is working fine. Had to cut the cat off (stuffed solid) (custom muffler shop ) and bypass the steering cooler too as it started leaking seriously.

Good luck.

 

[Wooluf1952]

Don't forget to check for pending codes.

 

[budwich]

IF your cruise works "briefly" by just turning the switch off and then on again, I think it is unlikely that you have a "code problem" dragging it down which means the reader isn't going to help.

 

[hellrazer]

Yeah i didnt see any codes set or stored when hooked up to my buddys scanner. Thanks again for all your help,
Jason