Help! Cruise control

[quick89]

1998 M6, cruise control works perfectly when in 4th gear, but will disengage immediately if in 5th or 6th gear. Corvette has 4:10 gears but worked previously.:ugh

 

[dadaroo]

 

[jrose7004]

Could be your steering sensor.

 

[quick89]

cruise control

1571 and 1255

 

[dadaroo]

1255 is the code of death for the EBCM. 1571 is related to Traction Control and could be the likely cause also.

Were these H or C codes? Most codes will show as H if you pull them after you turn the car off. Clear them and whenever it next drops drops out, without changing anything immediately read the PCM DTCs
.


The cruise control function comes out of the TAC module. It doesn't care what gear you are in so, the fifth/sixth gear selection itself should have nothing to do with it.

Try this, pull up on the Brake pedal with your foot and try the fifth gear test. Then do the same for the clutch.

Next. Put it in fourth and engage cruise. While in cruise, press the accelerator (while still in cruise) and accelerate and then let off and see if it drops out.


Here is the total description:

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.

 

[quick89]

cruise control

H codes with ignition off, no change lifting clutch or brake pedal, these switches work fine in all functions with car in 4th gear which would rule out a switch adjustment problem. Will check codes tonight with engine running

 

[quick89]

cruise control

reset DIC but get 1571H with engine running

 

[dadaroo]

Still waiting on this:

Put it in fourth and engage cruise. While in cruise, press the accelerator (while still in cruise) and accelerate and then let off and see if it drops out.

 

[dadaroo]

PS: Just this this for about 30 seconds.

 

[quick89]

cruise control

While in 4th gear with cruise engaged can accelerate and will resume at the preset speed, works perfectly. In 5th gear last night stayed engaged until I hit a significant bump in the road, no play in brake or clutch pedal , switch buttons on brake and clutch are completely depressed

 

[dadaroo]

I think the EBCM is at the root of your problem.