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 P21CB-00 or P21CC-00 are present, perform the confirmation procedure (diagnosis procedure) for these other DTCs first.

Are any applicable DTCs detected"

YES

Perform diagnosis of applicable DTC. Refer to DTC Index .

NO

GO TO 2 .
CHECK FOR CURRENT DEF HEATER CIRCUIT DTC
Check for DTC P20B8-00 current on the CONSULT screen.

Is applicable DTC current"

YES

GO TO 3 .

NO

Refer to Intermittent Incident .
INSPECT UREA HEATER RELAY AND CONNECTOR PINS
1. Turn ignition switch OFF.
2. Disconnect the urea heater relay.
3. Inspect urea heater relay and connector 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 UREA HEATER RELAY CIRCUIT
1. Replace urea heater relay with a known good relay.
2. Turn ignition switch ON.
3. Connect CONSULT and erase DTCs.
4. Using CONSULT, activate "DEF Tank Heater Test".
5. The DTC will move to "Past" when the test runs and passes.
Is P20B8-00 DTC current?

YES

GO TO 5 .

NO

Repair complete.
INSPECT DEF CONTROL MODULE AND VEHICLE HARNESS CONNECTOR PINS
1. Turn ignition OFF.
2. wait at least 90 seconds before proceeding to allow sufficient time for the DEF control module to completely power down.
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 6 .

NO

Repair or replace error-detected parts.

CHECK DEF TANK HEATER SUPPLY CIRCUIT FOR SHORT TO OTHER CIRCUITS

Check for continuity between DEF tank heater supply circuit and all other circuits at the DEF control module harness connector.

DEF control module			Continuity
Connector	Terminal	Terminal	Continuity
C35	1	All others	No

Is the inspection result normal?

YES

GO TO 7 .

Repair short circuit in harness or connectors.

CHECK THE UREA HEATER RELAY
1. Connect all harness connectors.
2. Turn ignition switch ON.
3. Connect CONSULT and erase all "ENGINE" diagnostic trouble codes.
4. Using CONSULT, activate "DEF Tank Heater Test".
5. The DTC will move to "Past" when the test runs and passes.
Is P20B8-00 DTC current?

YES

Replace the DEF control module. Refer to Removal and Installation .

NO

Inspection End.