If complaints are made about the above-mentioned vehicle, i.e. that the engine is irregular and not running smoothly and also that the engine control lamp is lit, these could be signs of a defect in the exhaust gas recirculation system (EGR system).
Fig. 1
- Pos. 1 = Differential pressure sensor
- Pos. 2 = Differential pressure measuring point
- Pos. 3 = EGR valve
- Pos. 4 = Exhaust gas recirculation solenoid valve
- Pos. 5 = Engine control unit
The following error codes could be saved in the error memory of the "Engine" system.
-P0401 "EGR return system / exhaust gas flow rate too low"
-P0402 "EGR return system / exhaust gas flow rate too high"
First of all, the pneumatic EGR valve is to be checked.
If no fault is found here, the differential pressure sensor should be regarded as a possible source of the trouble.
The measured values of the exhaust gas return rate are measured by the differential pressure sensor at the differential pressure measuring point (see Fig. 1). These values are forwarded as a voltage signal to the engine control unit. A technical fault could bring about an erroneous measurement of the amount of exhaust gas actually recirculated.
The two hose connections on the housing (see Fig. 2) are to be checked to ensure that they are in the correct position (input and output) and checks should also be run to search for any possible damage to the hose connections.
If no fault shows up here, everything points to a defect with the differential pressure sensor, in which case this sensor should be replaced.
A modified differential pressure sensor is available from the vehicle manufacturer.
Fig. 2
Important safety note
Technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only.
Reprinting, distribution, reproduction, exploitation in any form or disclosure of the contents of this document, even in part, is prohibited without our express, written approval and indication of the source. The schematic illustrations, pictures and descriptions serve only for the purposes of explanation and representation of the instructions and cannot be used as a basis for installation or assembly work. All rights reserved.
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