1 Catalytic converter exhaust gas temperature sensor
2 Oxidation catalytic converter
3 Exhaust gas temperature sensor – diesel particulate filter
4 Diesel particulate filter
The exhaust system of the 2.0L Duratorq-TDCi (DW) diesel engine incorporates a catalytic converter exhaust gas temperature sensor and a diesel particulate filter exhaust gas temperature sensor. The exhaust gas temperature of at least 500°C to 550°C required for the oxidation of the diesel particulates is detected by the exhaust gas temperature sensors and transmitted to the PCM. The exhaust gas temperature input parameters are used for calculation purposes by the PCM, which also takes other parameters into account. Depending on the exhaust gas temperature calculated, the PCM decides whether or not the regeneration process can be initiated. Through the arrangement of the two exhaust gas temperature sensors, the exhaust gas temperature required for regeneration can be adjusted and monitored very precisely. The regeneration process cannot be terminated unless a minimum temperature of 450 °C is reached and maintained.
Effects of faults
If a fault occurs at one of the two exhaust gas temperature sensors, the value of the other exhaust gas temperature sensor is used by the PCM.
If both exhaust gas temperature sensors are faulty, a substitute value is calculated based on the coolant temperature, engine load and engine speed.
Diagnosis
The following checks are carried out:
• short and open circuit (by means of a limit range check).
• logical rise/fall rate of the signal, whereby intermittent faults are detected (e.g. loose connector contacts),
• plausibility (following engine staring, a certain temperature increase is expected by the PCM).
A faulty exhaust gas temperature sensor has no direct influence on exhaust emissions. As regeneration is however significantly impaired, and clogging of the diesel particulate filter is possible, the MIL is actuated in the case of a fault. Therefore, they are MIL active components.
Possible diagnostic trouble codes (catalytic converter exhaust gas temperature sensor): P0425, P0426, P0427, P0428, P2080.
Possible diagnostic trouble codes (diesel particulate filter exhaust gas temperature sensor): P0435, P0436, P0437, P0438, P042A, P042B, P141E, P2084, P042C, P042D.
