Diagnostic Aids
Important: Perform the following in order to avoid misdiagnosis.
• Inspect for proper operation of brake lamps. • Inspect throttle linkage for mechanical binding which could cause
the system to malfunction. • Inspect cruise control cable adjustment, should have minimum slack. • EMI on the speed sensor signal circuit may cause erratic cruise
control operation.
Conditions for Enabling Cruise Control
The vehicle speed is greater than 40 km/h (25 mph).
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
SCHEMATIC REFERENCE: Cruise Control Schematics | ||||
1 | Did you perform A Diagnostic System Check - Cruise Control? | -- | Go to Step 2 | |
2 |
Does the test lamp illuminate? | -- | Go to Step 3 | Go to Step 29 |
3 | Probe the ignition positive voltage circuit of the cruise control module with a test lamp that is connected to the ground circuit of the cruise control module. Does the test lamp illuminate? | -- | Go to Step 4 | Go to Step 30 |
4 |
Does the test lamp illuminate on any of the circuits? | -- | Go to Step 14 | Go to Step 5 |
5 |
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 15 |
6 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 17 |
7 |
Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 18 |
8 | Probe the brake circuit with a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 19 |
9 | Press the brake pedal while monitoring the test lamp. Does the test lamp illuminate? | -- | Go to Step 20 | Go to Step 10 |
10 | Probe the cruise release circuit with a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | Go to Step 21 | Go to Step 11 |
11 | Press the brake pedal while monitoring the test lamp. Does the test lamp illuminate? | -- | Go to Step 12 | Go to Step 22 |
12 | Probe the cruise engaged output circuit with a DMM that is connected to a good ground. Does the voltage measure near the specified value? | B+ | Go to Step 13 | Go to Step 23 |
13 | Check the spedometer for proper operation. Does the speedometer operate properly? | -- | Go to Step 24 | |
14 | Test the circuit that illuminated the test lamp for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 27 |
15 | Test the on/off circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 16 |
16 | Test the ignition positive voltage circuit for an open or high resistance between the cruise control module and the cruise control switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 27 |
17 | Test the set/coast circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 27 |
18 | Test the resume/accelerate circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 27 |
19 | Test the brake circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 25 |
20 | Test the brake switch circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 25 |
21 | Test the cruise release circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 25 |
22 | Test the cruise release circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 25 |
23 | Test the cruise engaged output circuit for an open, a high resistance, or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 26 |
24 | Test the speed sensor circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 26 |
25 | Inspect for poor connections at the harness connector of the brake switch. 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 35 | Go to Step 31 |
26 | Inspect for poor connections at the harness connector of the VCM. 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 35 | Go to Step 32 |
27 | Inspect for poor connections at the harness connector of the cruise control switch. 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 35 | Go to Step 33 |
28 | 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 35 | Go to Step 34 |
29 | Repair the ignition positive voltage circuit of the cruise control module. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 35 | -- |
30 | Repair the ground circuit of the cruise control module. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 35 | -- |
31 | Replace the brake switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes. Did you complete the replacement? | -- | Go to Step 35 | -- |
32 | Replace the VCM. Refer to VCM Replacement/Programming in Engine Controls. Did you complete the replacement? | -- | Go to Step 35 | -- |
33 | Replace the multifunction turn signal lever. Refer to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle . Did you complete the replacement? | -- | Go to Step 35 | -- |
34 | Replace the cruise control module. Refer to Cruise Control Module Replacement . Did you complete the replacement? | -- | Go to Step 35 | -- |
35 | Operate the vehicle within the conditions for cruise control operation. Does the cruise control system operate correctly? | -- | System OK | Go to Step 2 |
