P0580-SPEED CONTROL SWITCH 1 CIRCUIT LOW





For a complete wiring diagram Refer to Section 8W.



Possible Causes
(V71) S/C SIGNAL 1 CIRCUIT SHORTED TO THE (V937) S/C RETURN CIRCUIT
(V71) S/C SIGNAL 1 CIRCUIT SHORTED TO GROUND
SPEED CONTROL SWITCH
PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).



Diagnostic Test

1. SPEED CONTROL SWITCH VOLTAGE LOW

NOTE: Do 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?

Yes


No

2. SPEED CONTROL SWITCH

Turn 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 kohms
On/Off - 0.47 kohms
Set - 5.49 kohms
Coast - 2.94 kohms
Cancel - 1.24 kohms
Resume/Accel - 15.4 kohms

Does the function on the Speed Control Switch have the correct resistance value?

Yes


No

3. SPEED CONTROL SWITCH

With 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?

Yes


No

4. (V71) S/C SIGNAL 1 CIRCUIT SHORTED TO THE (V937) S/C RETURN CIRCUIT



Turn 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?

Yes


No

5. (V71) S/C SIGNAL 1 CIRCUIT SHORTED TO GROUND



Measure 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?

Yes


No

6. SPEED CONTROL SWITCH VOLTAGE VALUES

Allow the engine to idle.
With a scan tool, monitor the S/C Switch voltage readings.

SWITCH POSITION
SWITCH No.1 VOLTAGE VALUE
SWITCH No.2 VOLTAGE VALUE
NO SWITCHES PRESSED
4.31 to 4.78 volts
 		4.31 to 4.78 volts
ON/OFF PRESSED
 		0.59 to 1.13 volts
 		3.53 to 3.92 volts
RES/ACCEL PRESSED
 		3.88 to 4.17 volts
 		2.04 to 2.47 volts
SET PRESSED
 		3.16 to 3.56 volts
 		1.17 to 1.56 volts
COAST PRESSED
 		2.57 to 2.94 volts
 		0.77 to 1.09 volts
CANCEL PRESSED
 		1.59 to 1.99 volts
 		2.84 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?

Yes


No

7. PCM

NOTE: Before 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?

Yes


No