Component Diagnostic Tests - Cruise Control

Refer to SCHEMATIC DIAGRAMS/ELECTRICAL AND ELECTRONIC DIAGRAMS for wiring diagrams.

Refer to COMPUTERIZED ENGINE CONTROLS for further computerized diagnostic procedures.

Refer to DIAGNOSTIC CHARTS for references to input tests.


TEST 1:

Test 1 - System Diagnosis:

1. Enter diagnostics and select BCM input BI75 and operate the cruise switch. Refer to chart 1.
^ If BCM input BI75 is correct, go to test 2.
^ If BCM input BI75 is not correct, go to input test BI75.

TEST 2:

Test 2 - System Diagnosis:

2. Enter BCM input BI71. Operate the brake pedal with the cruise switch "ON".
^ If BCM input BI71 is correct, go to test 3.
^ If BCM input BI71 is not correct, go to input test BI71.

TEST 3:

Test 3 - System Diagnosis:

3. Enter BCM input BI76. Operate the set switch with the cruise switch "ON".
^ If BCM input BI76 is correct, go to test 4.
^ If BCM input BI76 is not correct, go to input test BI76.

TEST 4:

Test 4 - System Diagnosis:

4. Enter BCM input BI77. Operate the cruise switch.
^ If BCM input BI77 is correct, go to test 5.
^ If BCM input BI77 is not correct, go to input test BI77.

TEST 5:

5. Enter BCM output BO01. Put the cruise switch "ON". BCM BO01 display and vent valve solenoid should both cycle.
^ If the vent valve solenoid cycles (audible clicking will be heard), go to test 6.
^ If the vent valve solenoid does not cycle, go to BCM trouble code B672.

TEST 6:

6. Enter BCM output BO02. Put the cruise switch "ON". BCM BO02 display and vacuum valve solenoid should both cycle.
^ If the vacuum valve solenoid cycles (audible clicking will be heard), go to test 7.
^ If the vacuum valve solenoid does not cycle, go to BCM trouble code B673.


TEST 7:

Test 7 - System Diagnosis:

7. Start the engine and run it for 2 minutes. Turn the engine "OFF". Enter BCM override BS05.
^ If the cruise control servo does not move fully in and out, go to test 8.
^ If tests 1 through 7 are all correct, replace the Body Computer Module (BCM).

TEST 8:


8. Check vacuum source, cruise control vacuum release valve and hoses for leaks, kinks or restrictions. Check the cruise control servo for mechanical binding.
^ If vacuum and mechanism are good, replace the cruise control servo.