P0579-S/C SWITCH #1 SIGNAL CIRCUIT PLAUSIBILITY





For a complete wiring diagram Refer to Section 8W



Possible Causes
(V937) S/C SWITCH GROUND OPEN
(V71) S/C SIGNAL #1 CIRCUIT OPEN
(V71) S/C SIGNAL #1 CIRCUIT SHORT TO GROUND
(V71) S/C SIGNAL #1 CIRCUIT SHORTED TO VOLTAGE
SPEED CONTROL SWITCH
ENGINE CONTROL MODULE

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



Diagnostic Test

1. VERIFY S/C SIGNAL CIRCUIT VOLTAGE

KEY
 		SIGNAL 1
 		SIGNAL 2
LO LIMIT
 		HI LIMIT
 		LO LIMIT
 		HI LIMIT
RELEASED
 		4.49
 		4.56
 		4.49
 		4.56
ON-OFF
 		0.85
 		1.00
 		3.67
 		3.75
SET
 		3.29
 		3.39
 		1.30
 		1.45
RESUME-ACCEL
 		3.98
 		4.05
 		2.17
 		2.29
CANCEL
 		1.72
 		1.82
 		2.98
 		3.08




NOTE: If the ECM detects and stores a DTC, the ECM also stores the engine/vehicle operating conditions under which the DTC was set. Some of these conditions are displayed on the scan tool at the same time the DTC is displayed.


NOTE: Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may assist when checking for an active DTC.


Turn the ignition off.
Disconnect the S/C Switch harness connector.
Turn the ignition on.
Measure the voltage of the (V71) S/C Signal #1 circuit at the S/C Switch harness connector.

Select the appropriate voltage reading.

4.5 to 5.5 volts.


Below 4.5 volts.


Above 5.5 volts.

2. (V937) S/C SWITCH GROUND OPEN



Turn the ignition off.
Disconnect the ECM harness connectors.
Measure the resistance of the (V937) S/C Switch Ground circuit between the S/C Switch harness connector and the ECM harness connector.

Is the resistance below 10.0 ohms?

Yes


No

3. ECM - SENSOR GROUND OPEN



Reconnect the S/C Switch harness connector.
Turn the ignition on.
With the scan tool, read the S/C Switch Voltage.
While monitoring the scan tool, connect a jumper wire between the (V71) S/C Signal #1 circuit and the (V937) S/C Switch Ground circuit in the S/C Switch harness connector.

Does the scan tool display below 0.1 volt with the jumper wire connected?

Yes


No

4. (V71) S/C SIGNAL #1 CIRCUIT OPEN



Turn the ignition off.
Disconnect the ECM harness connectors.
Measure the resistance between of the (V71) S/C Signal #1 circuit between the S/C Switch harness connector and the ECM harness connector.

Is the resistance below 10.0 ohms?

Yes


No

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



Measure the resistance between ground and the (V71) S/C Signal #1 circuit at the S/C Switch harness connector.

Is the resistance above 1000 ohms?

Yes


No

6. (V71) S/C SIGNAL #1 CIRCUIT SHORTED TO VOLTAGE



Turn the ignition off.
Disconnect the ECM harness connectors.
Remove the ASD Relay from the TIPM.
Connect a jumper wire between cavity 30 and cavity 87 of the ASD Relay connector.
Turn the ignition on.
Measure the voltage of the (V71) S/C Signal #1 circuit at the S/C Switch harness connector.

Is the voltage above 1.0 volt?

Yes


No