HINT:

1. For more information on the differential pressure sensor and TOYOTA D-CAT*1, refer to the following procedures.
2. If P1426 is present, refer to the DTC chart for TOYOTA D-CAT.

*1: Diesel Clean Advanced Technology.

 

The two sensing chambers of the differential pressure sensor are mounted to monitor the pressure before and after the DPNR*2 catalytic converter. The sensor itself is not located on the engine assembly in order to reduce the influence of vibration. The sensor is a semiconductor-type that is not influenced by exhaust gases.
The ECM compares the exhaust gas pressure before and after DPNR catalytic converter by monitoring the pressure using the upstream and downstream sensing chambers of the differential pressure sensor. If the difference between the pressure before and after the catalytic converter exceeds a predetermined level, the ECM judges that the catalytic converter is clogged with particulate matter (PM). When the ECM judges that a partially clogged condition exists, the ECM begins to perform DPNR catalyst regeneration.
*2: Diesel Particulate-NOx Reduction system

 

HINT:

If the vacuum hoses of the differential pressure sensor are incorrectly connected (crossed), the ECM interprets this as abnormal pressure difference, DTC P1426 (Differential Pressure Sensor [Installation]) will be set and the MIL will illuminate.

Toyota fault code list DTC P1426

DTC No.	DTC Detection Condition	Trouble Area
P1426	When output voltage from the differential pressure sensor indicates positive pressure as negative pressure (and vice versa) (1 trip detection logic)	Incorrect arrangement differential pressure sensor hose piping Differential pressure sensor vacuum hose is clogged Blockage in vacuum transmitting pipe sub-assembly Differential pressure sensor ECM

HINT:

1. DTC P1425 (Differential pressure sensor circuit), DTC P1427 (Differential pressure sensor circuit low) and/or DTC P1428 (Differential pressure sensor high) will be present if there is an open or short malfunction in the differential pressure sensor circuit.
2. After confirming DTC P1426, check the differential pressure in the "Powertrain / Engine and ECT / Data List / DPNR Differential Pressure" menu using the intelligent tester.

 

Reference: 

Condition	Differential Pressure Output	Sensor Condition
Ignition switch on (IG)	Approximately 0 kPa	Normal
Always	3 kPa	Open or short circuit
3,000 rpm (No engine load)	Negative output	Incorrect arrangement of hose piping

In order to detect abnormality in the differential pressure sensor, the ECM always monitors output voltage from the sensor. When the sensor output voltage is a reversal of positive and negative pressure, the ECM interprets this as incorrect vacuum hose arrangement of the sensor, or determines that the vacuum hoses have clogged, thus the MIL will be illuminated.
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1.CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P1426)

1. Connect the intelligent tester to the DLC3.

2. Turn the ignition switch on (IG) and turn the tester ON.

3. Enter the following menus: Powertrain / Engine and ECT / DTC.

4. Read DTCs.

    

   Result:

   Display (DTC Output)	Proceed to
   P1426	A
   P1426 and other DTCs	B

   HINT:

   If codes other than P1426 are output, perform troubleshooting for those DTCs first.

 

B	GO TO DTC CHART

A

2.CHECK CONNECTION OF VACUUM HOSE (DIFFERENTIAL PRESSURE SENSOR - VACUUM TRANSMITTING PIPE)

 

1. Check if the vacuum hose routing between the differential pressure sensor and the vacuum transmitting pipe is correct.

 

2. Check that there is no exhaust gas leakage between the differential pressure sensor and the vacuum transmitting pipe.

 

NG	CORRECT TO NORMAL CONNECTION

OK

3.CHECK BLOCKAGE OF VACUUM HOSE AND TRANSMITTING PIPE

 

CAUTION:

Be careful of being burned by exhaust gases during the following inspection.

 

1. Disconnect the vacuum hose (both upstream and downstream) on the differential pressure sensor.

2. Start the engine.

3. Check if there are exhaust gas pulsations from both vacuum hoses during idling.

 

NG	REPLACE CLOGGED PARTS

OK

4.READ VALUE OF DIFFERENTIAL PRESSURE

1. Connect the intelligent tester to the DLC3.

2. Turn the ignition switch on (IG) and turn the tester ON.

3. Enter the following menus: Powertrain / Engine and ECT / Data List / DPNR Differential Pressure.

4. Check that differential pressure is within the specification below.
    

    

   Result:
    

   Condition	Differential Pressure Output	Sensor Condition
   Ignition switch on (IG)	Approximately 0 kPa	Normal
   Always	3 kPa	Open or short circuit
   3,000 rpm (No engine load)	Negative output	Incorrect arrangement of hose piping

 

OK	CHECK FOR INTERMITTENT PROBLEMS

NG
REPLACE DIFFERENTIAL PRESSURE SENSOR ASSEMBLY