P20B8

P20B8-(DIESEL EXHAUST FLUID) REDUCTANT PUMP HEATER CONTROL CIRCUIT HIGH




For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation

The Diesel Exhaust Fluid (DEF) Supply Pump Assembly has an internal heater to prevent the fluid from freezing inside the pump. The power supply and control circuits are controlled by the DEF Dosing Control Unit. The DEF Supply Pump Heater is integrated into the DEF Supply Pump Assembly and is not serviced separately. The DEF Dosing Control Unit will illuminate the MIL light via the Powertrain Control Module (PCM) immediately after the diagnostics runs and fails and the line heater will be disabled. The DEF Dosing Control Module will turn off the MIL light via the PCM when the monitor runs and passes in three consecutive key cycles.

- When Monitored:
Continuously with the ignition on, and the heater commanded on.

- Set Condition:
The DEF Dosing Control Unit detects that the DEF Supply Pump heater circuit voltage is above a calibrated value.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC
1. Turn the ignition on, engine not running.
2. With the scan tool, navigate to Actuator Tests and actuate the DEF Supply Pump Heater.
3. With the scan tool, View DTCs.

Is the DTC Active?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION - 6.7L. . Intermittent Condition Test

2. CHECK THE RESISTANCE OF THE DEF SUPPLY PUMP HEATER
1. Turn the ignition off.
2. Disconnect the DEF Supply Pump Assembly harness connector.
3. Measure the resistance across the terminals of the DEF Supply Pump Heater circuits at the DEF Supply Pump Assembly.

Is the resistance above 2.0 Ohms?

Yes

- Go To 3

No

- Replace the DEF Supply Pump Assembly. Diesel Exhaust Fluid Pump Assembly - Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

3. CHECK THE (K471) DEF SUPPLY PUMP HEATER SUPPLY CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT




1. Disconnect the DEF Dosing Control Unit C1 harness connector.
2. Measure the resistance between the (K471) DEF Supply Pump Heater Supply circuit and all other circuits at the DEF Dosing Control Unit C1 harness connector.

Is the resistance above 10k Ohms between the (K471) DEF Supply Pump Heater Supply circuit and all other circuits?

Yes

- Go To 4

No

- Repair the short between the (K471) DEF Supply Pump Heater Supply circuit and the circuit that measured below 10k Ohms.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. CHECK THE (K472) DEF SUPPLY PUMP HEATER RETURN CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT




1. Measure the resistance between the (K472) DEF Supply Pump Heater Return circuit and all other circuits at the DEF Dosing Control Unit C1 harness connector

Is the resistance above 10k Ohms between the (K472) DEF Supply Pump Heater Return circuit and all other circuits?

Yes

- Replace the DEF Dosing Control Unit. Diesel Exhaust Fluid Dosing Control Unit - Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Repair the short between the (K472) DEF Supply Pump Heater Return circuit and the circuit that measured below 10k Ohms.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.