Code No. P0427: No. 2 Exhaust Gas Temperature Sensor (Catalyst Temperature) Circuit Low Input

OPERATION

• A power voltage of 5 V is applied to the No. 2 exhaust gas temperature sensor (catalyst temperature) output terminal from the engine-ECU connector terminal DTS2.
  
• The power voltage is earthed to the engine-ECU connector terminal DT2E from the No. 2 exhaust gas temperature sensor (catalyst temperature) connector terminal.
  

FUNCTION

• The No. 2 exhaust gas temperature sensor (catalyst temperature) converts the catalyst temperature into a voltage and inputs the voltage signal to the engine-ECU.
  
• Engine-ECU uses this voltage output for DPF regeneration control.
  
• The No. 2 exhaust gas temperature sensor (catalyst temperature) is a kind of resistor, which has characteristics to reduce its resistance as the catalyst temperature rises. Therefore, the sensor output voltage varies with the catalyst temperature, and becomes lower as the catalyst temperature rises.
  

TROUBLE JUDGMENT

• Battery positive voltage is 8 - 16 V
  
• 2 seconds later after the ignition switch has been in "ON" position or the engine has started up.
  

• The No. 2 exhaust gas temperature sensor (catalyst temperature) output voltage is 0.255 V or less.
  

FAIL-SAFE AND BACKUP FUNCTION

• The throttle valve is opened (Electrical discontinuity).
  
• The EGR control is stopped (fully closed).
  
• The DPF regeneration is prohibited.
  
• The AS&G control is prohibited.
  

PROBABLE CAUSES

• Failed No. 2 exhaust gas temperature sensor (catalyst temperature)
  
• Short circuit in No. 2 exhaust gas temperature sensor (catalyst temperature) circuit or loose connector contact
  
• Failed engine-ECU
  

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

	Go to Step 2.

	Go to Step 3.

	Repair or replace the connector, or replace the No. 2 exhaust gas temperature sensor (catalyst temperature). After replacing the No. 2 exhaust gas temperature sensor (catalyst temperature), carry out the forcible DPF regeneration. (Refer to GROUP 17 - Emission Control <DIESEL> - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).

	Go to Step 4.

	Repair or replace the connector, or repair the damaged harness wire.

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

	Replace the engine-ECU.