P0580-SPEED CONTROL SWITCH 1 CIRCUIT LOWFor a complete wiring diagram Refer to Section 8W.When Monitored:With the ignition key on.Set Condition:Speed control switch input No.1 is below the minimum acceptable voltage at the PCM. One trip fault.
Possible Causes(V71) S/C SIGNAL 1 CIRCUIT SHORTED TO THE (V937) S/C RETURN CIRCUIT(V71) S/C SIGNAL 1 CIRCUIT SHORTED TO GROUNDSPEED CONTROL SWITCHPCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).Diagnostic Test1.SPEED CONTROL SWITCH VOLTAGE LOWDo not press the Speed Control Switch button.Ignition on, engine not running.With a scan tool, read the Speed Control voltage.Is the Speed Control voltage below 1.0 volt?YesGo To 2NoRefer to the INTERMITTENT CONDITION Diagnostic Procedure.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)2.SPEED CONTROL SWITCHTurn the ignition off.Remove and disconnect the Speed Control Switch from the steering wheel per Service Information.Measure the resistance across each Speed Control Switch.Monitor the ohmmeter while pressing each function button for each switch.The following resistance specs are taken between terminals (V71) S/C Signal 1 circuit and (V937) S/C Return circuit of the Switch when holding the switch button in the following positions.Not pressing any switch - 20.5 kohmsOn/Off - 0.47 kohmsSet - 5.49 kohmsCoast - 2.94 kohmsCancel - 1.24 kohmsResume/Accel - 15.4 kohmsDoes the function on the Speed Control Switch have the correct resistance value?YesGo To 3NoReplace the Speed Control Switch.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)3.SPEED CONTROL SWITCHWith the scan tool, monitor the Speed Control Switch voltage.Disconnect the Speed Control Switch harness connector per Service Information.Did the voltage change to above 4.8 volts?YesReplace the Speed Control Resume/Accel Switch.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 44.(V71) S/C SIGNAL 1 CIRCUIT SHORTED TO THE (V937) S/C RETURN CIRCUITTurn the ignition off.Disconnect the C3 PCM harness connector.Measure the resistance between the (V937) S/C Return circuit and the (V71) S/C Signal 1 circuit at the S/C Switch harness connector.Is the resistance below 5.0 ohms?YesRepair the short between the (V71) S/C Signal 1 circuit and the (V937) S/C Return circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 55.(V71) S/C SIGNAL 1 CIRCUIT SHORTED TO GROUNDMeasure the resistance between ground and the (V71) S/C Signal 1 circuit in the S/C Switch harness connector.To help determine the location of a short, disconnect the Steering Column Control Module C2 and C5 harness connectors and see if the short goes away.Is the resistance below 100 ohms?YesRepair the short to ground in the (V71) S/C Signal 1 circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 66.SPEED CONTROL SWITCH VOLTAGE VALUESAllow the engine to idle.With a scan tool, monitor the S/C Switch voltage readings.
SWITCH POSITIONSWITCH No.1 VOLTAGE VALUESWITCH No.2 VOLTAGE VALUENO SWITCHES PRESSED 4.31 to 4.78 volts4.31 to 4.78 voltsON/OFF PRESSED0.59 to 1.13 volts3.53 to 3.92 voltsRES/ACCEL PRESSED3.88 to 4.17 volts2.04 to 2.47 voltsSET PRESSED3.16 to 3.56 volts1.17 to 1.56 voltsCOAST PRESSED2.57 to 2.94 volts0.77 to 1.09 voltsCANCEL PRESSED1.59 to 1.99 volts2.84 to 3.25 volts
Take these same voltage measurements with a voltmeter by back probing the (V71) S/C Signal 1 circuit at the switch.Compare the voltage readings on the voltmeter to what the scan tool displayed.Are the voltage readings out of the listed specification and is there less than a 0.2 of a volt difference between the voltmeter switch values and the scan tool switch value?YesReplace the Speed Control Switch.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 77.PCMBefore continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.Were there any problems found?YesRepair as necessary.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoReplace and program the Powertrain Control Module per Service Information.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)