For 1990-2009 cars

## Cruise Control Inoperative/Malfunctioning L81

### Diagnostic Aids

Caution: Refer to SIR Caution in the Preface section.

Disable the inflatable restraint steering wheel module when performing this diagnostic table. Refer to SIR Disabling and Enabling in SIR.

Ensure that the following cruise control switches are not stuck in the engaged position:

• | On/Off switch

• | Set/Coast switch

• | Resume/Accel switch

Perform the following in order to avoid misdiagnosis:

• | Inspect for proper operation of the stop lamps. Refer to Exterior Lighting Systems Description and Operation in Wiring Systems.

• | Rotate the steering wheel to both steering stops and activate each cruise control switch separately. With a scan tool, observe the associated Cruise Control Switch parameter in the Idle/Speed Control data list. This will help eliminate the possibility of a internally open or shorted inflatable restraint steering wheel module coil.

• | EMI on the speed sensor signal circuit may cause erratic cruise control operation.

• | For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Cruise Control Schematics Connector End View Reference: Engine Control Module Connector End Views in Engine Controls - 3.0L (L81)
1 | Did you perform the Cruise Control Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Cruise Control
2 |

1. Install a scan tool.
2. Turn the ignition ON, with the engine OFF.
3. Turn the cruise control On/Off switch OFF.
4. With the scan tool, observe the following Cruise Control parameters in the Idle/Speed Control data list:

• | Cruise Switch

• | Cruise Resume/Accel

• | Cruise Set/Coast

Do all of the parameters listed above display Off?

Go to Step 3

Go to Step 6

3 |

1. With the scan tool, observe the Cruise Switch parameter.
2. Turn the cruise On/Off switch ON.

Does the Cruise Switch parameter display On?

Go to Step 4

Go to Step 7

4 |

1. With the scan tool, observe the Cruise Set/Coast parameter.
2. Press and hold the Set/Coast button.

Does the Cruise Set/Coast parameter display On?

Go to Step 5

Go to Step 13

5 |

1. With the scan tool, observe the Cruise Resume/Accel parameter.
2. Press and hold the Resume/Accel button.

Does the Cruise Resume/Accel parameter display On?

Go to Diagnostic Aids

Go to Step 14

6 |

1. Turn the ignition OFF.
2. Disconnect the cruise switch.
3. Turn the ignition ON, with the engine OFF.
4. With the scan tool, observe the following Cruise Control parameters in the Idle/Speed Control data list:

• | Cruise Switch

• | Cruise Resume/Accel

• | Cruise Set/Coast

Do all of the parameters listed above display Off?

Go to Step 15

Go to Step 9

7 |

1. Turn the ignition OFF.
2. Disconnect the cruise switch.
3. Turn the ignition ON, with the engine OFF.
4. Connect a test lamp between the ignition 3 voltage circuit and a good ground.

Does the test lamp illuminate?

Go to Step 8

Go to Step 17

8 |

1. Connect a 3-ampere fused jumper between the ignition 3 voltage circuit and the cruise control on switch signal circuit.
2. With the scan tool, observe the Cruise Switch parameter.

Does the Cruise Switch parameter display On?

Go to Step 15

Go to Step 12

9 | 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 20 | Go to Step 10
10 | Test the cruise control set/coast 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 20 | Go to Step 11
11 | Test the cruise control resume/accel 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 20 | Go to Step 16
12 | 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 20 | Go to Step 16
13 | Test the cruise control set/coast 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 20 | Go to Step 15
14 | Test the cruise control set/coast 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 20 | Go to Step 15
15 | Inspect for poor connections at the harness connector of the cruise control switch. 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 20 | Go to Step 18
16 | 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 20 | Go to Step 19
17 | Repair the open, the short to ground, or the high resistance in the ignition circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 20 | --
18 | Replace the cruise control switch. Refer to Steering Wheel Control Switch Assembly Replacement in Steering Wheel and Column. Did you complete the replacement? | Go to Step 20 | --
19 | Important: Program the replacement ECM. Replace the ECM. Refer to Engine Control Module Replacement in Engine Controls - 3.0L (L81). Did you complete the replacement? | Go to Step 20 | --
20 |

1. Enable the inflatable restraint steering wheel module. Refer to SIR Disabling and Enabling in SIR.
2. Operate the vehicle with in the conditions for cruise control operation.

Does the cruise control system operate properly?

System OK

Go to Step 2

## Cruise Control Inoperative/Malfunctioning L61

### 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 | Go to Diagnostic System Check - Cruise Control
2 |

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

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 |

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

Does the test lamp illuminate on any of the circuits?

--

Go to Step 14

Go to Step 5

5 |

1. Turn ON the ignition, with the engine OFF.
2. Turn ON the cruise control switch.
3. Probe the cruise control on/off 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 15

6 |

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

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 17

7 |

1. Probe the cruise control resume/accelerate 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 18

8 | Probe the TCC/Brake 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 19
9 | Press the brake pedal while monitoring the test lamp. Does the test lamp go out? | -- | Go to Step 10 | Go to Step 20
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 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 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 13 | Go to Step 23
13 | Check the speedometer for proper operation. Does the speedometer operate properly? | -- | Go to Step 24 | Go to Symptoms - Instrument Panel, Gages and Console in Instrument Panel, Gages and Console
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 cruise control on switch signal circuit for a open, high resistance or short to ground. 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 a open, high resistance or short to ground 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 cruise control set/coast 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 35 | Go to Step 27
18 | Test the cruise control resume/accelerate 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 35 | Go to Step 27
19 | Test the TCC/Brake 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 35 | Go to Step 25
20 | Test the TCC/Brake 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 35 | Go to Step 25
21 | Test the stop lamp 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 35 | Go to Step 25
22 | Test the stop lamp 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 35 | Go to Step 25
23 | Test the cruise control engaged signal circuit for an open, a high resistance, or a short to ground. 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 a open, high resistance or short to ground between the cruise control module and the PCM. 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 stop lamp 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 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 35 | Go to Step 34
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 32
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 33
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 stop lamp switch. Refer to Stop Lamp Switch Replacement in Lighting Systems. Did you complete the replacement? | -- | Go to Step 35 | --
32 | Replace the cruise controlfFunction switch. Refer to Cruise Control Switch Replacement in Cruise Control. Did you complete the replacement? | -- | Go to Step 35 | --
33 | Replace the cruise control module. Refer to Cruise Control Module Replacement . Did you complete the replacement? | -- | Go to Step 35 | --
34 | Important: The PCM must be reprogrammed after replacement. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls. 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