Chrysler 300/300 Touring/300C, Dodge Magnum. Manual — part 1145

P0643-PRIMARY 5-VOLT SUPPLY CIRCUIT HIGH

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
Ignition on.

•

Set Condition:
When the PCM recognizes the Primary 5-volt Supply circuit voltage is too high. One Trip Fault. ETC light is
flashing.

Possible Causes

(F855) PRIMARY 5-VOLT SUPPLY SHORTED TO BATTERY VOLTAGE

PCM

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

Diagnostic Test

1.

ACTIVE DTC

Ignition on, engine not running.

With a scan tool, read DTCs.

Is the DTC active at this time?

Yes

>> Go To 2

No

>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

2.

(F855) PRIMARY 5-VOLT SUPPLY SHORTED TO BATTERY VOLTAGE

Turn the ignition off.

Disconnect the PCM harness connectors.

Disconnect all the Sensors that share the (F855) Primary 5-volt Supply
circuit.

NOTE: Improperly installed aftermarket accessories can cause this
DTC to set. Check for wiring added by customer.
Ignition on, engine not running.

Measure the voltage on the (F855) Primary 5-volt Supply circuit at the
CKP Sensor harness connector.

Is the voltage above 5.2 volts?

Yes

>> Repair the short to battery voltage in the (F855) Primary

5-volt Supply circuit.

Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Go To 3

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ENGINE ELECTRICAL DIAGNOSTICS

LX

3.

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

>> Repair as necessary.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Replace and program the Powertrain Control Module per Service Information.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

LX

ENGINE ELECTRICAL DIAGNOSTICS

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P0645-A/C CLUTCH RELAY CIRCUIT

For a complete wiring diagram Refer to Section 8W.

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ENGINE ELECTRICAL DIAGNOSTICS

LX

•

When Monitored:
With the ignition on. Battery voltage greater than 10 volts. A/C Switch on.

•

Set Condition:
An open or shorted condition is detected in the A/C clutch relay control circuit. One Trip Fault. Three good trips
to turn off the MIL.

Possible Causes

INTERNAL FUSED IGNITION SWITCH OUTPUT CIRCUIT

(C13) A/C CLUTCH RELAY CONTROL CIRCUIT OPEN

(C13) A/C CLUTCH RELAY CONTROL CIRCUIT SHORTED TO GROUND

A/C CLUTCH RELAY

PCM

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

Diagnostic Test

1.

A/C CLUTCH RELAY OPERATION

Ignition on, engine not running.

With a scan tool, actuate the A/C Clutch Relay.

Is the A/C Clutch Relay operating?

Yes

>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Go To 2

2.

A/C CLUTCH RELAY RESISTANCE

Turn the ignition off.

Remove the A/C Clutch Relay from the IPM.

Measure the resistance of the A/C Clutch Relay Coil.

Is the resistance between 60 to 80 ohms?

Yes

>> Go To 3

No

>> Replace the A/C Clutch Relay.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

3.

INTERNAL FUSED B+ CIRCUIT

Ignition on, engine not running.

Using a 12-volt test light connected to ground, probe the Internal Fused B+ circuit in the connection.

Does the test light illuminate brightly?

Yes

>> Go To 4

No

>> Repair the open or short to ground in the Internal Fused B+ circuit. Check and replace any open fuses.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

LX

ENGINE ELECTRICAL DIAGNOSTICS

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