Dodge Ram Truck 1500-2500-3500. Manual — part 1110

P0642-LOW VOLTAGE AT THE #2 SENSOR SUPPLY CIRCUIT (CONTINUED)

For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS)

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
With the key on.

•

Set Condition:
Voltage detected on the #2 sensor supply circuit is below a calibrated value.

Possible Causes

FAN CLUTCH ASSEMBLY

(K668) 5-VOLT SHORTED TO GROUND

(K668) 5-VOLT SUPPLY SHORTED TO ANOTHER CIRCUIT

FAN DTC

INTERMITTENT CONDITION

ECM

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

Diagnostic Test

1.

FAN CLUTCH ASSEMBLY

Disconnect the Fan clutch harness connector.

NOTE: Check connectors - Clean/repair as necessary.
With the scan tool, read DTCs.

Did P0483 set?

Yes

>> Replace the Fan clutch assembly.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)

No

>> Go To 2

9 - 1362

ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL

DR/DH

P0642-LOW VOLTAGE AT THE #2 SENSOR SUPPLY CIRCUIT (CONTINUED)

2.

(K668) 5-VOLT SHORTED TO GROUND

Turn the ignition off.

Disconnect the ECM harness connector.

NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between the (K668) #2 5-volt supply (fan
speed sensor power) circuit in the sensor harness connector and bat-
tery negative.

Is the resistance greater than 100k Ohms?

Yes

>> Go To 3

No

>> Repair the #2 (K668) 5-volt supply shorted to ground.

Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)

3.

(K668) 5-VOLT SUPPLY SHORTED TO ANOTHER CIRCUIT

Measure the resistance between the sensor (K668) #2 5-volt supply
(fan speed sensor power) circuit in the ECM harness connector to all
other circuits in the ECM harness connectors

Is the resistance greater than 100k Ohms?

Yes

>> Go To 4

No

>> Repair the 5-volt supply shorted to another circuit.

Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)

DR/DH

ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL

9 - 1363

P0642-LOW VOLTAGE AT THE #2 SENSOR SUPPLY CIRCUIT (CONTINUED)

4.

FAN DTC

Reconnect the ECM harness connectors.

Reconnect the disconnected Fan harness connector.

Turn the ignition on.

With the scan tool, read DTCs.

Is DTC P0483 set?

Yes

>> Repair the Fan DTC.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)

No

>> Go To 5

5.

ECM

Turn the ignition off.

Disconnect the Fan harness connector.

Turn the ignition on.

Measure the voltage between the sensor (K668) #2 5-volt supply (fan
speed sensor power) circuit at the fan clutch harness connector and
the fan speed sensor ground.

Is the voltage between 4.5 and 5.5 volts?

Yes

>> Refer to the INTERMITTENT CONDITION Symptom

(Diagnostic Procedure). (Refer to 9 - ENGINE - DIAGNO-
SIS AND TESTING)

No

>> Replace the ECM.

Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)

9 - 1364

ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL

DR/DH

P0643-HIGH VOLTAGE AT THE #2 SENSOR SUPPLY CIRCUIT

DR/DH

ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL

9 - 1365