For 1990-2009 cars

### 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.

• | Inspect for stored Diagnostic Trouble Codes (DTCs) in the PCM.

• | 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 Cruise Control System Check ? | -- | Go to Step 2 | Go to Cruise Control System Check
2 |

1. Turn OFF the ignition.
2. Disconnect the cruise control module.
3. Turn the ignition to the RUN position.
4. Probe the ignition positive voltage circuit of the cruise control module harness connector with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 3

Go to Step 36

3 | Probe the ignition positive voltage circuit of the cruise control module harness connector with a test lamp that is connected to the ground circuit of the cruise control module harness connector. Does the test lamp illuminate? | -- | Go to Step 4 | Go to Step 37
4 |

1. Turn OFF the cruise control.
2. Probe the cruise control module harness connector, on/off switch, set/coast switch, and the resume/accelerate switch signal circuits with a test lamp that is connected to a good ground.

Does the test lamp illuminate on any of the signal circuits?

--

Go to Step 16

Go to Step 5

5 |

1. Turn ON the cruise control switch.
2. Probe the cruise control module harness connector on/off switch signal circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 17

6 |

1. Probe the cruise control module harness connector set/coast switch signal circuit with a test lamp that is connected to a good ground.
2. Press and hold the SET/COAST button.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 19

7 |

1. Probe the cruise control module harness connector resume/accelerate switch signal circuit with a test lamp that is connected to a good ground.
2. Press and hold the RESUME/ACCEL switch.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 20

8 | Probe the cruise control module harness connector Abs/TCC, 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 21
9 | Press the brake pedal while monitoring the test lamp. Does the test lamp illuminate? | -- | Go to Step 22 | 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 23 | 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 24
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 25 | 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 26
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 27
15 | Check the speedometer for proper operation. Does the speedometer operate properly? | -- | Go to Step 28 | Go to Speedometer and/or Odometer Inoperative
16 | Test the signal circuit that illuminated the test lamp for a short to voltage. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 34
17 | 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. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 18
18 | Test the ignition positive voltage circuit for an open or high resistance between the IP junction block and the cruise control switch. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 34
19 | Test the cruise control set/coast signal circuit for an open or a high resistance. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 34
20 | Test the cruise control resume/accelerate signal circuit for an open or a high resistance. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 34
21 | Test the cruise control release switch signal circuit for an open or a high resistance. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 29
22 | Test the cruise control release switch signal circuit for a short to voltage. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 29
23 | Test the stoplamp switch signal circuit for a short to voltage. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 30
24 | Test the stoplamp switch signal circuit for an open or a high resistance. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 30
25 | Test the cruise inhibit signal circuit for a short to ground. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 33
26 | Test the cruise inhibit signal circuit for an open, a high resistance, or a short to voltage. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 33
27 | Test the cruise engaged signal circuit for an open, a high resistance, or a short to voltage. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 33
28 | Test the speed sensor circuit for an open or a high resistance between the PCM and cruise control module. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 35
29 | Inspect the cruise control release switch for proper adjustment. Refer to Cruise Release Switch Adjustment . Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 31
30 | Inspect the stoplamp switch for proper adjustment. Refer to Stop Lamp Switch Adjustment in Hydraulic Brakes. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 32
31 | Inspect for poor connections at the harness connector of the cruise control release switch. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 38
32 | Inspect for poor connections at the harness connector of the stoplamp switch. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 39
33 | Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 40
34 | Inspect for poor connections at the harness connector of the cruise control switch. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 39
35 | Inspect for poor connections at the harness connector of the cruise control module. Did you find and correct the condition? | -- | Go to Step 43 | Go to Step 42
36 | 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 43 | --
37 | Repair the ground circuit of the cruise control module. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 43 | --
38 | Replace the cruise control release switch. Refer to Cruise Control Release Switch Replacement . Did you complete the replacement? | -- | Go to Step 43 | --
39 | Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes. Did you complete the replacement? | -- | Go to Step 43 | --
40 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls. Did you complete the replacement? | -- | Go to Step 43 | --
41 | Replace the cruise control switch. Refer to Multifunction Lever Replacement . Did you complete the replacement? | -- | Go to Step 43 | --
42 | Replace the cruise control module. Refer to Cruise Control Module Replacement . Did you complete the replacement? | -- | Go to Step 43 | --
43 | Operate the vehicle within the conditions for cruise control operation. Does the cruise control system operate correctly? | -- | System OK | Go to Step 2