Dodge Ram Truck 1500-2500-3500. Manual — part 1085

P0477-LOW VOLTAGE ON THE ENGINE BRAKE DRIVER

For the Engine circuit diagram (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES/ENGINE CON-
TROL MODULE - SCHEMATIC - ELECTRICAL)

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
When the ignition is on.

•

Set Condition:
When the signal from the engine brake driver output does not match the signal from the engine brake driver
feedback.

Possible Causes

WIRING HARNESS

ENGINE BRAKE DRIVER RELAY

FUSED B+ OPEN

ENGINE BRAKE DRIVER SIGNAL CIRCUIT OPEN

INTERMITTENT CONDITION

ENGINE BRAKE DRIVER SIGNAL CIRCUIT SHORTED TO BATTERY NEGATIVE

ECM

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

Diagnostic Test

1.

RELAY CLICKING

Turn the engine off (ignition on).

With the scan tool, actuate the exhaust brake relay.

Can you hear the Relay clicking?

Yes

>> Go To 2

No

>> Go To 3

2.

WIRING HARNESS

With the scan tool, actuate the exhaust brake relay.

While the relay is clicking, wiggle the wiring harness and connectors throughout the circuit.

Does this interrupt the clicking?

Yes

>> Repair or replace the wiring harness.

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

9 - 1262

ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL

DR/DH

P0477-LOW VOLTAGE ON THE ENGINE BRAKE DRIVER (CONTINUED)

3.

Engine Brake Driver Relay

Remove the Engine Brake Driver Relay.

Check connectors - Clean/repair as necessary.

Measure the resistance between terminals 86 and 85 of the engine brake relay.

Is the resistance less than 100 Ohms?

Yes

>> Go To 4

No

>> Replace the Engine Brake Driver Relay.

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

4.

FUSED B+ OPEN

Ignition on, engine not running.

Measure the voltage of the Fused B+ Supply circuit at the Engine Brake Relay.

Is the voltage within 10% of battery voltage?

Yes

>> Go To 5

No

>> Repair the open B+ circuit.

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

5.

ENGINE BRAKE DRIVER SIGNAL CIRCUIT OPEN

Turn the ignition off.

Disconnect the ECM harness connectors.

Check connectors - Clean/repair as necessary.

Measure the resistance of the Engine Brake Driver signal circuit between the Relay harness connector and the ECM
harness connector.

Is the resistance less than 10 Ohms?

Yes

>> Go To 6

No

>> Repair the open Engine Brake driver circuit open from relay to ECM.

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

6.

ENGINE BRAKE DRIVER SIGNAL CIRCUIT SHORTED TO BATTERY NEGATIVE

Measure the resistance of the Engine Brake Driver signal circuit between the Relay connector and battery negative.

Is the resistance greater than 100k Ohms?

Yes

>> Go To 7

No

>> Repair Engine brake driver shorted to Battery negative.

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 - 1263

P0477-LOW VOLTAGE ON THE ENGINE BRAKE DRIVER (CONTINUED)

7.

ECM

Reconnect the ECM harness connectors.

Using the scan tool, actuate the Engine Brake Driver Relay.

While monitoring with the scan tool, use a jumper wire to connect 12 volts to the relay signal circuit with the relay
disconnected.

Did the DTC P0478?

Yes

>> Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 9 - ENGINE -

DIAGNOSIS AND TESTING)

No

>> Replace ECM.

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

9 - 1264

ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL

DR/DH

P0478-HIGH VOLTAGE ON THE ENGINE BRAKE DRIVER

For the Engine circuit diagram (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES/ENGINE CON-
TROL MODULE - SCHEMATIC - ELECTRICAL)

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
When the ignition is on.

•

Set Condition:
When the signal from the engine brake driver output does not match the signal from the engine brake driver
feedback.

Possible Causes

RELAY LOOSE

ENGINE BRAKE DRIVER CONTROL CIRCUIT SHORTED TO VOLTAGE

ENGINE BRAKE RELAY

INTERMITTENT CONDITION

ECM

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

Diagnostic Test

1.

RELAY

Ignition on, engine not running.

With the scan tool, actuate the Engine Brake Driver Relay.

Can you hear the Relay clicking?

Yes

>> Go To 2

No

>> Go To 3

2.

RELAY LOOSE

While the relay is clicking, wiggle the wiring harness and connectors.

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 - 1265