Dodge Ram Truck 1500-2500-3500. Manual — part 1112
P0646-LOW VOLTAGE DETECTED AT THE A/C CLUTCH RELAY (CONTINUED)
3.
A/C CLUTCH RELAY
Remove the A/C Clutch Relay from the PDC.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between terminals 85 and 86 of the A/C
Clutch Relay.
Is the resistance less than 100 Ohms?
Yes
>> Go To 4
No
>> Replace the A/C clutch relay.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
4.
FUSED BATTERY SUPPLY
Ignition on, engine not running.
Measure the voltage on the Fused Battery Supply circuit in the PDC.
Is the voltage within 1 volt of battery voltage?
Yes
>> Go To 5
No
>> Repair the open Fused battery supply.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
9 - 1370
ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL
DR/DH
P0646-LOW VOLTAGE DETECTED AT THE A/C CLUTCH RELAY (CONTINUED)
5.
(C13) A/C SIGNAL CIRCUIT OPEN
Turn the ignition off.
Disconnect the ECM harness connectors.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance of the (C13) A/C Clutch signal circuit between the PDC and the ECM harness connector.
Is the resistance less than 10 Ohms?
Yes
>> Go To 6
No
>> Repair the open (C13) A/C signal circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
6.
(C13) A/C SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance of the (C13) A/C Clutch signal circuit between the PDC and battery negative.
Is the resistance greater than 100k Ohms?
Yes
>> Go To 7
No
>> Repair the (C13) A/C signal circuit shorted to ground.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
7.
ECM
Reconnect the ECM harness connectors.
Using the scan tool, actuate the A/C Clutch Relay
While monitoring with the scan tool, use a jumper wire to connect 12 volts to the relay signal cavity (85) in the PDC
with the relay disconnected.
Did DTC P0647 set?
Yes
>> Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
No
>> Replace the ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
DR/DH
ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL
9 - 1371
P0647-HIGH VOLTAGE DETECTED AT THE A/C CLUTCH RELAY
9 - 1372
ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL
DR/DH
P0647-HIGH VOLTAGE DETECTED AT THE A/C CLUTCH RELAY (CONTINUED)
For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS)
For a complete wiring diagram Refer to Section 8W.
•
When Monitored:
When the ignition is on.
•
Set Condition:
When the signal from the A/C Clutch output does not match the signal from the A/C Clutch feedback.
Possible Causes
LOOSE CONNECTION
SHORTED TO EXTERNAL VOLTAGE
FUSED BATTERY SUPPLY
A/C CLUTCH RELAY
INTERMITTENT CONDITION
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.
CLUTCH CLICKING
Ignition on, engine not running.
With the scan tool, actuate the A/C clutch relay.
Can you hear the Relay clicking?
Yes
>> Go To 2
No
>> Go To 3
2.
LOOSE CONNECTION
Actuation still running.
While the relay is clicking, wiggle the wiring harness and connectors throughout the circuit.
Does this interrupt the clicking?
Yes
>> Repair the loose connection.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No
>> Go To 3
DR/DH
ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL
9 - 1373
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