Reading and Clearing Diagnostic Trouble Codes

Fig. 2 Data Link Connector Location:

When trying to verify a speed control system electronic malfunction: Connect a DRB scan tool if available to the data link connector. The connector is located at left side of the steering column, and at lower edge of the panel.

If a scan tool is not available, use the following procedure:
1. With key inserted in ignition switch, cycle switch to ON position three times. On third cycle, leave switch in ON position.
2. After switch has been cycled three times, observe MALFUNCTION INDICATOR LAMP (check engine) indicator on instrument cluster. If a diagnostic code is present, indicator will flash (blink) in a series which will show which diagnostic code is the problem. Example: A series of three flashes in rapid succession, a slight pause, then four flashes in rapid succession would indicate diagnostic code 34.
3. A speed control malfunction may occur without either diagnostic code being indicated. If no diagnostic code appears or diagnostic code 15 or 34 is observed, refer to the appropriate flow chart.

Speed Control Accelerates Or Taps Up By Itself
Check for diagnostic trouble codes. If code 15 refer to the Powertrain Diagnostic Procedure, if code 34 perform the following test:
1. Conduct the speed control switch test on the RESUME/ACCEL switch.
2. If it fails, replace switch.
3. If it passes, disconnect the 4 way connector at servo. Test continuity of pin 1 to ground to test for intermittent short. Wiggle wires while preforming test.
4. If continuity to ground, repair wiring.
5. If no continuity to ground, replace PCM.

Speed Control Slows Down By Itself
Test vehicle speed sensor, refer to Instrument panel and warning gauges/Instrument panel. If sensor fails replace sensor, if it passes perform the following test:
1. Perform the speed control switch test on the SET/COAST switch, if it fails replace switch.
2. If the switch passes, conduct the vacuum supply test.
3. If it passes, conduct the servo vacuum test. If it fails replace servo.
4. If it passes, test continuity of pin 2 of harness connector to PCM pin 80 for intermittent open. Wiggle wires while performing this test. If no continuity to pin 80, repair harness for open.
5. If no continuity, replace the PCM.

Speed Control Will Not Resume-sets OK
Perform the speed control switch test on the RESUME/ACCEL switch. If the switch fails replace switch.

Speed Control Diagnostic Trouble Codes:

1. If switch passes, check continuity from RESUME/ACCEL switch connector pin 1 to pin 31 of 40 way connector at PCM. Check for intermittent open circuit, wiggle wires while performing test.
2. If intermittent open, repair circuit.
3. If continuity is ok, perform continuity test from pin 1 of RESUME/ACCEL switch connector to ground. Check for intermittent short, wiggle wires while performing this test.
4. If shorted, repair harness for short.

Speed Control Will Not Slow Down
Check for diagnostic trouble codes. If code 34 or no code present, perform the following test:
1. Conduct the speed control switch test on the resume SET/COAST.
2. If it fails replace switch.
3. f it passes use an ohmmeter to test continuity between pin 2 of SET/COAST switch connector and ground. Wiggle wires while preforming test. If no continuity repair circuit.
4. If continuity, test continuity between pin 1 of SET/COAST switch connector and pin 41 of the PCM 40 way connector. Wiggle wires while preforming test. If no continuity, repair circuit.
5. If continuity, disconnect the servo connector. Test continuity from pin 2 of connector and ground to test for intermittent short. Wiggle wires while preforming test. If continuity repair circuit.
6. If no continuity, conduct the servo vacuum test. If it fails replace servo.
7. If it passes, replace the PCM.