Cant find the engine controller while installing the cruise control

No fuse
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 Descriptionfor 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.

Does the light come on ?

DTC P0575: Cruise Control Switch Signal Circuit
DTC B3794 08: Cruise Control Function Request Circuit Signal Invalid
DTC B3794 61: Cruise Control Function Request Circuit Actuator Stuck
DTC B0835 00: Cruise Control System Active Indicator Circuit
The cruise control switch contains an LED that illuminates to indicate the cruise control system has been switched ON. Voltage is applied through the ON/OFF switch to the LED when the switch is pressed. The body control module (BCM) provides the ground path for the LED through a dedicated LED control circuit. Pressing the switch again opens the switch and the lamp turns OFF.
DTC P0571: Cruise Control Brake Switch Circuit
DTC P0703: Brake Switch Circuit

Your best bet , take it to a qualified repair shop .

Which engine does your trailblazer have 5.3 or 4.2 L
Cruise Control Description and Operation (5.3L)
Cruise Control Description and Operation (4.2L)
makes a difference ! The best way to start diagnostic's is with a scan tool . May have DTC'S diagnostic trouble codes .
DTC P1574 Stop Lamp Switch Circuit
DTC P0568 Cruise Control Set Switch Circuit
DTC P0567 Cruise Control Resume Switch Circuit
Plus with a scan tool you can see if the cruise control switch is inputing to PCM. Data list .
The cruise control resume/accel switch is an input to the powertrain control module (PCM). The PCM uses the cruise control resume/accel switch signal circuit in order to detect when the driver has requested to accelerate the set vehicle speed or to resume the cruise control system. The PCM detects a voltage signal on the cruise control resume/accel switch signal circuit when the switch is applied. This DTC sets if the PCM senses voltage on the cruise control resume/accel switch signal circuit for longer than 90 seconds.
Cruise Control Indicator Inoperative (4.2L)
Turn OFF the ignition.
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With the scan tool, Command the Cruise Control Lamp Test parameter ON, in the instrument panel cluster (IPC) Output Controls.
Does the Cruise indicator illuminate in the IPC?
YES - Go to Step 3
no - Go to Step 4
3
Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?
YES - Go to Step 7
NO - Go to Step 6
4
Inspect for poor connections at the harness connector of the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?
YES - Go to Step 7
NO - Go to Step 5
5
Replace the IPC. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?
YES - Go to Step 7
--
6
Replace the PCM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?
Go to Step 7
--
7
Operate the system in order to verify the repair.
Does the system operate properly?
System OK
Go to Step 2

Cruise Control Inoperative/Malfunctioning (4.2L)

Install a scan tool.
Turn ON the ignition, with the engine OFF.
Press the cruise ON/OFF switch OFF.
With the scan tool, observe the Cruise ON/OFF switch parameter in the powertrain control module (PCM) Cruise Control Data list.
Does the Cruise ON/OFF switch parameter display OFF?

Your best bet mite be to take your vehicle to the dealer .

cruise controls are controlled by several units
VSS or road speed sensor, clutch and brake sensors , engine speed (tacho) and the on/off switch
cruise controls will disengage automatically if the road speed is too slow ( higher for manuals than autos ) so if the road speed is below around 20mph it may not engage at all as the VSS says it is too slow for the engine rpms
check all sensors for adjustment

The power for the cruise control comes through fuse #14 in the fuse box. From there it goes to the Cruise Control Switch. However, the Cruise Control Module is above the Fuse/Relay box, behind the dash board. Good-Day!

If the cruise control makes the engine seem to run very rough until disengaging it, there could be a problem with the engine itself. As, most cruise control systems just pull on the throttle cable to maintain speed on the highway based on setting the speed with the button.

So, I would look into the engine maybe having an issue with spark plugs, or wires, or another tuneup or mechanical issue.


Cruise Control Cable Removal & Installation To Remove:

1. Before servicing the vehicle refer to the precautions at the beginning of this section.
2. Remove or disconnect the following:
   • The cable from the throttle lever and the accelerator control cable bracket
     
     
   • The cable from the module by rotating the cable counter clockwise at the module
   • The cable from the module band

To Install:
NOTE: Ensure that the module strap is not twisted during cable installation

1. Install or connect the following:
   • The cable to the module band
   • The cable to the module
   • The cable to the throttle lever and the accelerator control cable bracket
2. Adjust the cruise control cable.

Cruise Control Module Removal & Installation To Remove:

1. Before servicing the vehicle refer to the precautions at the beginning of this section.
2. Remove or disconnect the following:
   
   
   • The cruise control cable from the module
     
     
   • The electrical connector
     
     
   • The mounting bracket bolt from the cruise control module
   • The cruise control module from the mounting bracket

To Install:

1. Install or connect the following:
   • The cruise control module to the mounting bracket
   • The mounting bracket bolt to the cruise control module
     1. Torque to 53 inch lbs.(6 Nm)
   • The electrical connector to the module
   • The cruise control cable to the module

The Dashboard light dimmer control is probably stopped working because one of the tiny eletronic bits inside it has died. A temporary fix is to remove the connecting plug on the rear of the unit and put a bridging wire across the terminals. The cruise control problem could have several causes. They operate on engine vacuum so check the hose going to the cruise control unit in the engin bay from the inlet manifold. If the hose is cracked or hard there will not be enough vacuum to operate the cruise control.

Hello. If the engine light or ABS is on then the cruse control will not work.

you cant "unplug" anything on the car to disconnect the cruise,it can be taken off the V.I.D block by your local dealer on I.D.S.

Not really sure on parts pricing (probably very expensive) but very complicated and work intensive to install... Need to get the engine computer reprogrammed for cruise control, install all the wiring (to the brake light switch, the speed sensors, etc...) install the servo/vacuum motor and cables to the throttle assembly...

does cruise show up in led when you start engine