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. |
| • | When testing vehicles with steering wheel controls, the steering wheel must be rotated to each stop position while testing the cruise control switch signal circuits. This will assure the integrity of the SRI coil. |
| • | EMI on the speed sensor signal circuit may cause erratic cruise control operation. |
Conditions for Enabling Cruise Control
| • | When vehicle speed is more than 40 km/h (25 mph) |
| • | When PARK, REVERSE, NEUTRAL, or 1st gear is not indicated. |
| • | When an over/undercharged battery condition does not exist. |
| • | With normal engine RPM. |
| • | Without high engine RPM (fuel cut-off). |
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 40 |
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 41 |
4 |
Does the test lamp illuminate on any of the signal circuits? | -- | Go to Step 18 | Go to Step 5 |
5 |
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 19 |
6 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 21 |
7 |
Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 22 |
8 | Probe the cruise control release signal circuit with a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 23 |
9 | Press the brake pedal while monitoring the test lamp. Does the test lamp illuminate? | -- | Go to Step 24 | Go to Step 10 |
10 | Probe the stop lamp signal circuit with a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | Go to Step 25 | 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 26 |
12 | Probe the cruise control inhibit signal circuit with a test lamp that is connected to B+. Does the test lamp illuminate? | -- | Go to Step 29 | Go to Step 13 |
13 | Use a scan tool in order to command the cruise inhibit/enable OFF. Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 30 |
14 | Probe the cruise control engaged signal circuit with a DMM that is connected to a good ground. Does the voltage measure near the specified value? | B+ | Go to Step 15 | Go to Step 31 |
15 |
Important: If equipped with a cancel switch (Oldsmobile) use steps 15, 16. Vehicles with out cancel switch go to step 17.
Does the test lamp illuminate? | -- | Go to Step 16 | Go to Step 27 |
16 | Press the cruise control cancel switch while monitoring the test lamp. Does the test lamp illuminate? | -- | Go to Step 28 | Go to Step 17 |
17 | Check the speedometer for proper operation. Does the speedometer operate properly? | -- | Go to Step 32 | |
18 | Test the signal 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 47 | Go to Step 34 |
19 | Test the cruise control on switch signal circuit for an open or a high resistance and the set/coast and resume/accel signal circuits for a short to ground.. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 47 | Go to Step 20 |
20 | Test the ignition positive voltage circuit for an open or high resistance between the IP junction block 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 47 | Go to Step 38 |
21 | Test the cruise control set/coast signal 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 47 | Go to Step 38 |
22 | Test the cruise control resume/accelerate signal 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 47 | Go to Step 38 |
23 | Test the cruise control release switch signal 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 47 | Go to Step 33 |
24 | Test the cruise control release switch signal 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 47 | Go to Step 33 |
25 | Test the stoplamp switch signal 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 47 | Go to Step 34 |
26 | Test the stoplamp switch signal 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 47 | Go to Step 34 |
27 | Test the cruise control cancel circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 47 | Go to Step 38 |
28 | Test the cruise control cancel 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 47 | Go to Step 38 |
29 | Test the cruise inhibit signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 47 | Go to Step 37 |
30 | Test the cruise inhibit signal 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 47 | Go to Step 37 |
31 | Test the cruise engaged signal 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 47 | Go to Step 37 |
32 | Test the speed sensor circuit for an open or a high resistance between the PCM and cruise control module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 47 | Go to Step 39 |
33 | Inspect the cruise control release switch for proper adjustment. Refer to Brake Release Switch Adjustment. Did you find and correct the condition? | -- | Go to Step 47 | Go to Step 35 |
34 | Inspect the stoplamp switch for proper adjustment. Refer to Stop Lamp Switch Adjustment. Did you find and correct the condition? | -- | Go to Step 47 | Go to Step 36 |
35 | Inspect for poor connections at the harness connector of the cruise control release 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 47 | Go to Step 42 |
36 | Inspect for poor connections at the harness connector of the stoplamp 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 47 | Go to Step 43 |
37 | Inspect for poor connections at the harness connector of the PCM. 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 47 | Go to Step 44 |
38 | Inspect for poor connections at the harness connector of the cruise control switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairsin Wiring Systems. Did you find and correct the condition? | -- | Go to Step 47 | Go to Step 45 |
39 | Inspect for poor connections at the harness connector of the cruise control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairsin Wiring Systems. Did you find and correct the condition? | -- | Go to Step 47 | Go to Step 46 |
40 | 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 47 | -- |
41 | Repair the ground circuit of the cruise control module. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 47 | -- |
42 | Replace the cruise control release switch. Refer to Brake Release Switch Replacement. Did you complete the replacement? | -- | Go to Step 47 | -- |
43 | Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes. Did you complete the replacement? | -- | Go to Step 47 | -- |
44 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming 2.4L or Powertrain Control Module Replacement/Programming 3.4L in Engine Controls. Did you complete the replacement? | -- | Go to Step 47 | -- |
45 | Replace the cruise control switch. Refer to Cruise Control Switch Replacement. Did you complete the replacement? | -- | Go to Step 47 | -- |
46 | Replace the cruise control module. Refer to Cruise Control Module Replacement. Did you complete the replacement? | -- | Go to Step 47 | -- |
47 | Operate the vehicle within the conditions for cruise control operation. Does the cruise control system operate correctly? | -- | System OK | Go to Step 2 |
