im been looking for a cruise control vaccum schematic
for my 2002 c5. had it in the shop for a head light repair , got the light fixed but the cruise control diddnt work any more. they worked on it for 2 days no luck,so i made them stop so i can take it to another mech that i have more faith in.
he thinks it a vac problem,he may be full of crap also.

 

he thinks it a vac problem,he may be full of crap also.
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Yelp, find another Mech.

 

Don't think GM has used vacuum for cruise in many moons.

 

Throttle by wire = no vacuum control

 

There is no vacuum used. Must be a mechanic who works on old cars. Obviously not experienced with drive by wire throttle controls.

Have you used the DIC to check for diagnostic codes? If not you should do that before going to that shop. Also check the stop lamp switch and clutch switch if you have a clutch.

Here is a description of the Vette's cruise control operation. Been this way since 1997.
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 TCC/brake switch
• The stop lamp switch
• The throttle actuator control (TAC) module
• The Clutch Pedal Position (CPP) switch, if equipped with a manual transmission

Cruise Control Engaged


The TAC module monitors the signal circuits of the following cruise control switches:

• On/Off
• Resume/Accel
• Set/Coast

The PCM will engage and adjust vehicle speed based on the information received from the TAC module via the UART serial data link. For further information on the TAC system, refer to Throttle Actuator Control (TAC) System Description in Engine Controls--5.7 L.
The cruise control switches are located on the multifunction/turn signal lever.
Ignition positive voltage is supplied from the 10 ampere CR CONT fuse to the cruise control switch via the ignition 1 voltage circuit. When the normally open cruise control On/Off switch is turned On, the switch closes and the TAC module 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 TAC module 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 TAC sends a UART message to the PCM, in order to confirm that the cruise control enable criteria has been met. 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 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 TAC module 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 PCM disengages the cruise control operation based on the information received from the TAC module. The TAC module monitors the signal circuits of the following switches:

• The On/Off switch
• The TCC/brake switch
• The stop lamp switch
• The CPP 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 TAC module monitors the stop lamp switch signal circuit and the PCM monitors the TCC brake switch/cruise control release signal circuit. When the brake pedal is pressed, the normally closed TCC brake switch opens and the normally open stoplamp switch closes. The TAC module detects a high signal voltage on the stop lamp switch signal circuit and the PCM detects a low signal voltage on the TCC brake switch/cruise control release signal circuit. The TAC module sends a UART message to the PCM indicating the status of the stop lamp switch. 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 Off button is activated, or the ignition switch is turned off.
The clutch switch is mounted to the clutch pedal bracket. Depressing the clutch pedal while the cruise control is engaged will disengaged the cruise control system. When the clutch pedal is depressed, the normally closed clutch switch closes and the PCM detects a low signal voltage on the clutch switch signal circuit.
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 IPC in order to deactivate the cruise control indicator.

Cruise Control Inhibited


The PCM inhibits the cruise control operation when any of the following conditions exist:

• 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 volts and 16 volts.
• The antilock brake system/traction control system is active for more than 2 seconds

There are several cruise control related diagnostic codes:
DTC P0567 DTC P0568 DTC P0571 DTC P0704 DTC P1574

Bill

 

humm good info ,thanks bill

 

Hmmmm....makes me wonder why I'm having such a difficult time finding a vacuum schematic for the headlight doors......

 

i have checked the DIC and theirs no codes,he connected a hand held scaner and their was no codes their either.

 

Ok. I assume the fuse #20 in the passenger footwell was checked. Please explain what the shop checked while trying to repair the cruise control.

 

Thanks Bill, I copied and filed.

 

yeah fuses is good,i will get the schematics and scan them,they high lighted what they checked,they told me but it was greek to me.
the schmatics below ,the lines that are highlighted have been checked.


http://s1004.photobucket.com/albums/...rent=Page1.jpg

http://s1004.photobucket.com/albums/...rent=Page2.jpg

 

per the schematics and the shop.

checked hot in on start to pcm fuse 16 to conn id through a3 c1 to G106..good

HOT AT ALL TIMES ,to IGN RELAY 42 engign 1 fuse 19.. good
cpp checked good
tcc checked good.hot at all times stp haz fuse 8 . good
stop lamp switch good.throttle actuator control module (TAC) is circled ?

hot in on and start ,cr cont fuse 20 ,to c1 1239 c217 cruise control on switch signal good
cruise control set/coast good
cruise control resume/accel good
(TAC) is circled ?
thats all i got for m them and the schematics

my other mech looked at it ,he dont think they was tring to hard to find the problem. they had it for 2 days before i got pissed and told them to stop.
on a side note when it in for the head light repair,driver side they replaced the plastic cover that goes over the igntion switch.