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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1315 (CRUISE CONTROL SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC 012TEST DESCRIPTION
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Test Description

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Test Description
WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 2:  This step tests the resistance of the cruise control servo magnetic clutch circuit.
  2. 4:  This step tests the stop lamp switch.
  3. 7:  This step tests the cruise control actuator arm for free movement with the magnetic clutch de-energized.
  4. 8:  This step tests the cruise control actuator arm for a malfunction with the magnetic clutch energized.
DTC 012

Step Action Value(s) Yes No
Schematic Reference: Cruise Control Schematics 
1 Did you perform the Diagnostic System Check - Cruise Control  ? - Go to Step 2  Go to Diagnostic System Check - Cruise Control 
2 
  1. Turn OFF the ignition.
  2. Disconnect the cruise control module connector which is located behind the instrument panel.
  3. Measure the resistance between cavity 8 of the cruise control module connector and ground.
Is the resistance within the specified range?		 35-45 Ω Go to Step 3  Go to Step 4 
3
  1. Disconnect the cruise control servo connector.
  2. Test the servo ground circuit for a high resistance or an open condition. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 14  Go to Step 7 
4 
  1. Disconnect the stop lamp switch connector.
  2. Measure the resistance between cavity 3 and 4 of the stop lamp switch.
  3. Observe the resistance reading while pressing and releasing the brake pedal.
Does the resistance read infinite Ω while the pedal is pressed, and 0 Ω when the pedal is released?		 - Go to Step 5  Go to Step 9 
5 Test the magnetic clutch control circuit between the cruise control module and the cruise control servo for an open or ground condition. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 14  Go to Step 6 
6
  1. Disconnect the cruise control servo connector.
  2. Measure the resistance between cavity 3 and cavity 4 of the cruise control servo connector.
Is the resistance within the specified range?		 35-45 Ω Go to Step 7  Go to Step 11 
7 
  1. Disconnect the cruise control cable from the actuator.
  2. Move the actuator arm back and forth.
Does the actuator arm move freely in both directions?		 - Go to Step 8  Go to Step 13 
8 
  1. Disconnect the cruise control servo connector.
  2. Connect a fused jumper wire from ground to terminal 4 of the cruise control servo.
  3. Connect a fused jumper wire from B+ to terminal 3 of the cruise control servo.
  4. Attempt to move the actuator arm.
Does the actuator arm move?		 - Go to Step 11  Go to Step 10 
9 Adjust or replace the stop lamp switch. Refer to Stop Lamp Switch Adjustment or Stop Lamp Switch Replacement .
Is the adjustment or replacement complete?		 - Go to Step 14  -
10 Inspect for poor connections at the harness connector of the cruise control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 14  Go to Step 12 
11 Inspect for poor connections at the harness connector of the cruise control servo. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 14  Go to Step 13 
12 Replace the cruise control module. Refer to Cruise Control Module Replacement .
Did you complete the replacement?		 - Go to Step 14  -
13 Replace the cruise control servo. Refer to Cruise Control Servo Replacement .
Did you complete the replacement?		 - Go to Step 14  -
14
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Pull the cruise control switch to the CANCEL position and hold.
  4. While holding the cruise control switch to the CANCEL position, push the cruise control ON switch 5 times within 3 seconds.
  5. Check that the CRUISE indicator lamp flashes rapidly. This confirms that any flash codes have been cleared.
Does the CRUISE indicator lamp flash the same trouble code?		 - Go to Step 2  System OK
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.