Symptom:
P0579-S/C SWITCH SIGNAL CIRCUIT SIGNAL VOLTAGE TOO
HIGH
POSSIBLE CAUSES
ECM - S/C SIGNAL CIRCUIT OPEN
ECM - S/C SIGNAL CIRCUIT SHORTED TO VOLTAGE
ECM - SENSOR GROUND OPEN
S/C SWITCH GROUND CIRCUIT OPEN
S/C SWITCH SIGNAL CIRCUIT OPEN
S/C SWITCH SIGNAL CIRCUIT SHORTED TO VOLTAGE
SPEED CONTROL SWITCH
INTERMITTENT CONDITION
TEST
ACTION
APPLICABILITY
1
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 DRB 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 on.
With the DRB, erase ECM DTCs.
Test drive the vehicle and activate the Speed Control.
At some point during the test drive, move the S/C Switch to each of its positions.
With the DRB, read ECM DTCs.
Did this DTC set again?
All
Yes
→ Go To 2
No
→ Go To 7
2
Turn the ignition off.
Disconnect the S/C Switch harness connector.
Turn the ignition on.
Measure the voltage of the S/C Switch Signal circuit.
Select the appropriate voltage reading.
All
Below 4.5 volts.
Go To
3
Between 4.5 and 5.5 volts.
Go To
4
Above 5.5 volts
Go To
6
120
DRIVEABILITY - DIESEL