Chrysler Town, Dodge Caravan. Manual — part 1145
Symptom:
P0579-S/C SWITCH SIGNAL CIRCUIT PLAUSIBILITY
POSSIBLE CAUSES
INTERMITTENT CONDITION
HIGH RESISTANCE IN THE S/C SWITCH SIGNAL CIRCUIT
HIGH RESISTANCE IN THE S/C SWITCH GROUND CIRCUIT
S/C SWITCHES
ENGINE CONTROL MODULE
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, actuate each of the S/C Switch buttons.
With the DRB, read ECM DTCs.
Did this DTC set again?
All
Yes
→ Go To 2
No
→ Go To 5
2
Turn the ignition off.
Disconnect the S/C Switch harness connectors.
Disconnect the ECM harness connectors.
Measure the resistance of the S/C Switch Signal circuit.
Is the resistance below 5.0 ohms?
All
Yes
→ Go To 3
No
→ Repair the S/C Switch Signal circuit for high resistance.
Perform SPEED CONTROL VERIFICATION - VER-4.
3
Turn the ignition off.
Disconnect the S/C Switch harness connectors.
Disconnect the ECM harness connectors.
Measure the resistance of the S/C Switch Ground circuit.
Is the resistance below 5.0 ohms?
All
Yes
→ Go To 4
No
→ Repair the S/C Switch Ground circuit for high resistance.
Perform SPEED CONTROL VERIFICATION - VER-4.
123
DRIVEABILITY - DIESEL
TEST
ACTION
APPLICABILITY
4
Turn the ignition off.
Replace the S/C Switches.
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, actuate each of the S/C Switch buttons.
Monitor the DRB for ECM DTCs.
Did this DTC set again?
All
Yes
→ Replace and program the Engine Control Module in accordance
with the Service Information.
Perform SPEED CONTROL VERIFICATION - VER-4.
No
→ The repair is complete.
Perform SPEED CONTROL VERIFICATION - VER-4.
5
WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRB
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the
conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?
All
Yes
→ Repair as necessary.
Perform SPEED CONTROL VERIFICATION - VER-4.
No
→ Test Complete.
124
DRIVEABILITY - DIESEL
P0579-S/C SWITCH SIGNAL CIRCUIT PLAUSIBILITY —
Continued
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 ON/OFF/SET SWITCH
S/C ON/OFF/SET SWITCH SIGNAL CIRCUIT OPEN
S/C SWITCH SIGNAL CIRCUIT SHORTED TO VOLTAGE
SENSOR GROUND OPEN
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 off.
Disconnect the S/C ON/OFF/SET button 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.
Between 4.5 and 5.5 volts.
Above 5.5 volts
2
Turn the ignition off.
Disconnect the S/C ON/OFF/SET Switch harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the S/C Switch Signal circuit.
Is the resistance below 10.0 ohms?
All
Yes
→ Replace and program the Engine Control Module in accordance
with the Service Information.
Perform SPEED CONTROL VERIFICATION - VER-4.
No
→ Repair the S/C ON/OFF/SET Switch Signal circuit for an open.
Perform SPEED CONTROL VERIFICATION - VER-4.
125
DRIVEABILITY - DIESEL
TEST
ACTION
APPLICABILITY
3
Turn the ignition off.
Disconnect the S/C ON/OFF/SET switch harness connector.
Turn the ignition on.
Connect a jumper wire between the S/C Switch Signal circuit and the Sensor Ground
at the ON/OFF/SET Switch harness connector.
With the DRB, read the S/C Switch volts.
Does the DRB display below 0.5 volt?
All
Yes
→ Replace the S/C ON/OFF/SET Switch.
Perform SPEED CONTROL VERIFICATION - VER-4.
No
→ Go To 4
4
Turn the ignition off.
Disconnect the S/C ON/OFF/SET Switch harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the Sensor Ground circuit.
Is the resistance below 10.0 ohms?
All
Yes
→ Replace and program the Engine Control Module in accordance
with the Service Information.
Perform SPEED CONTROL VERIFICATION - VER-4.
No
→ Repair the Sensor Ground circuit for an open.
Perform SPEED CONTROL VERIFICATION - VER-4.
5
Turn the ignition off.
Disconnect the S/C ON/OFF/SET Switch harness connector.
Disconnect the ECM harness connectors.
Turn the ignition on.
Measure the voltage of the S/C Switch Signal circuit.
Is the voltage above 1.0 volt?
All
Yes
→ Repair the S/C ON/OFF/SET Switch Signal circuit for a short to
voltage.
Perform SPEED CONTROL VERIFICATION - VER-4.
No
→ Replace and program the Engine Control Module in accordance
with the Service Information.
Perform SPEED CONTROL VERIFICATION - VER-4.
126
DRIVEABILITY - DIESEL
P0579-S/C SWITCH SIGNAL CIRCUIT SIGNAL VOLTAGE TOO HIGH —
Continued
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