Diagnosis Procedure

WARNING: This page is about a different car, the 2018 Nissan Titan XD. However, it is still accessible from the selected car via links, so may be relevant.

CHECK DTC PRIORITY
1. Turn ignition switch ON.
2. Connect CONSULT and check for other existing "ENGINE" diagnostic trouble codes.
If DTC P21C4-00 is present, perform the confirmation procedure (diagnosis procedure) for this other DTC first.

Is applicable DTC detected?

YES

Perform diagnosis of applicable DTC. Refer to DTC Description .

NO

GO TO 2 .
CHECK FOR CURRENT DEF LINE HEATER CIRCUIT DTC
Check for DTC P20B9-00 current on the CONSULT screen.

Is applicable DTC current?

YES

GO TO 3 .

NO

Refer to Intermittent Incident .
INSPECT DEF CONTROL MODULE LINE HEATER AND CONNECTOR PINS
1. Turn ignition OFF.
2. Disconnect the DEF line heater from the harness.
3. Disconnect the DEF control module.
4. Inspect both connectors for the following:
  - Loose connector.
  - Corroded pins.
  - Bent or broken pins.
  - Pushed back or expanded pins.
  - Moisture in or on the connector.
  - Missing or damaged connector seals.
  - Dirt or debris on or in the connector pins.
  - Connector shell broken.
  - Wire insulation damage.
  - Damaged connector locking tab.
Is the inspection result normal?

YES

GO TO 4 .

NO

Repair or replace error-detected parts.

CHECK DEF LINE HEATER SUPPLY CIRCUIT FOR OPEN

Check the power supply circuit for continuity between the DEF control module and the DEF line heater.

DEF control module		DEF line heater		Continuity
Connector	Terminal	Connector	Terminal	Continuity
C205	15	C202	1	Yes

Is the inspection result normal?

YES

GO TO 5 .

Repair open power supply circuit in harness or connectors.

CHECK DEF LINE HEATER GROUND CIRCUIT FOR OPEN

Check the ground supply circuit for continuity between the DEF control module and the DEF line heater.

DEF control module		DEF line heater		Continuity
Connector	Terminal	Connector	Terminal	Continuity
C205	30	C202	2	Yes

Is the inspection result normal?

YES

GO TO 6 .

Repair open ground circuit in harness or connectors.

CHECK THE DEF LINE HEATER INTEGRITY
Check the DEF line heater resistance. Refer to Component Inspection .

Is the inspection result normal?

YES

GO TO 7 .

NO

Replace the DEF line heater. Refer to Exploded View .
CHECK FOR CURRENT DTC
1. Connect all harness connectors.
2. Turn ignition switch ON.
3. Connect CONSULT and erase ENGINE diagnostic trouble codes.
4. Using CONSULT, activate "DEF Line Heater Test".
5. The DTC will move to "Past" when the test runs and passes.
Is P20B9-00 DTC current?

YES

Return to diagnostic procedure. Refer to DTC Description .

NO

Repair complete.