Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 540 (CRUISE CONTROL SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESCRUISE CONTROL INOPERATIVE/MALFUNCTIONING (3.6L)CONDITIONS FOR ENABLING CRUISE CONTROL
1999 GMC Forward Control 5.7 R, Automatic
Conditions for Enabling Cruise Control
1999 GMC Forward Control 5.7 R, AutomaticSECTION Conditions for Enabling Cruise Control
WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
- The vehicle speed is greater than 40 km/h (25 mph).
- The vehicle is not in PARK, REVERSE, NEUTRAL, or 1st gear.
- The system voltage is between 11 volts and 16 volts.
Cruise Control Inoperative/Malfunctioning (3.6L)
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Cruise Control Schematics Connector End View Reference: Cruise Control Connector End Views or to Engine Control Module (ECM) Connector End Views in Engine Controls - 3.6L (LY7) |
|||
| 1 | Did you perform the Cruise Control Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Cruise Control (3.4L) or Diagnostic System Check - Cruise Control (3.6L) |
| 2 |
|
Go to Step 3 | Go to Step 6 |
| 3 |
|
Go to Step 4 | Go to Step 7 |
| 4 |
|
Go to Step 5 | Go to Step 17 |
| 5 |
|
Go to Step 8 | Go to Step 18 |
| 6 |
|
Go to Step 12 | Go to Step 20 |
| 7 |
|
Go to Step 10 | Go to Step 13 |
| 8 | Do the stop lamps operate properly? | Go to Step 9 | Go to Stop Lamps Inoperative or to Stop Lamps Always On in Lighting Systems |
| 9 |
|
Go to Diagnostic Aids | Go to Step 11 |
| 10 |
|
Go to Step 20 | Go to Step 16 |
| 11 | Test the stop lamp signal circuit for an open or for a high resistance between the stop lamp switch and the engine control module (ECM). Refer to Circuit Testing
and to Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 21 |
| 12 | Test the cruise control on switch signal circuit for a short to voltage. Refer to Circuit Testing
and to Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 21 |
| 13 | Test the cruise control on switch signal circuit for a short to ground. Refer to Circuit Testing
and to Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 14 |
| 14 | Test the cruise control set/coast switch signal circuit for a short to ground. Refer to Circuit Testing
and to Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 15 |
| 15 | Test the cruise control resume/accelerate switch signal circuit for a short to ground. Refer to Circuit Testing
and to Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 19 |
| 16 | Test the cruise control on switch signal circuit for an open, for a short to ground, or for a high resistance. Refer to Circuit Testing
and to Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 21 |
| 17 | Test the cruise control set/coast signal circuit for an open, for a short to ground, or for a high resistance. Refer to Circuit Testing
and to Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 20 |
| 18 | Test the cruise control resume/accelerate signal circuit for an open, for a short to ground, or for a high resistance. Refer to Circuit Testing
and to Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 20 |
| 19 | Repair the open, the high resistance, or the short to ground in the ignition 1 voltage circuit. Refer to Circuit Testing
and to Wiring Repairs
in Wiring Systems. Did you complete the repair? |
Go to Step 24 | - |
| 20 | Inspect for poor connections at the harness connector of the multifunction turn signal lever. Refer to Testing for Intermittent Conditions and Poor Connections
and to Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 22 |
| 21 | Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections
and to Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 23 |
| 22 | Replace the multifunction turn signal lever. Refer to Multifunction, Turn Signal Switch Replacement
in Steering Wheel and Column. Did you complete the replacement? |
Go to Step 24 | - |
| 23 |
IMPORTANT:
Program the replacement ECM. Replace the ECM. Refer to Engine Control Module (ECM) Replacement
in Engine Controls - 3.6L (LY7).Did you complete the replacement? |
Go to Step 24 | - |
| 24 | Operate the vehicle within the conditions for cruise control operation. Does the cruise control system operate properly? |
System OK | Go to Step 2 |
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.