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A fix for that dreaded antipollution fault? by Merrick Hilton

This article appeared in the Australian August 2017 issue of TORQUE and appeared to be relevant to us as well.

My 2002 406HDi manual wagon has generally been free of any major faults during its life of 500,000 kms. Although the vehicle has had regular and attentive maintenance every 10,000kms it was not unexpected, given its age, that at some stage it would experience some complex problems.
In the past 15 months the vehicle has been plagued by a persistent anti-pollution fault (APF). The APF initiated “limp mode” operation. Whilst in limp mode the vehicle was still driveable. Limp mode prevented the engine spinning past 3000rpm so a deal of short shifting was required to get it on the move. Cruise control was also disabled.
The fault, initially intermittent, became a permanent feature in the Latter part of 2016. An increase in fuel consumption was evident and the engine was also “running on” for several seconds after the ignition was turned off.
The vehicle was diagnosed as having a P1138 fault code. The code indicated there was a fault generated somewhere in the fuel/air delivery system. The difficulty was in pinning down the actual component and related sensor which was causing the alert.
I became an avid reader of posts in Peugeot forums which described the issue. It appeared that there are several components and sensors which could prompt an APF. The conponents are a small fuel regulator motor which is attached to the high pressure fuel pump, a sensor on the common rail and the mass airflow (MAF) sensor located immediately behind an air intake filter box.
Forums mentioned the need to check all electrical connections and related wiring connected to the above mentioned components. This was done and everything appeared to be in good repair. Some forum posts indicated a variety of fairly complex engine management problems which could be associated with the P1138 code. I tried to keep things simple by focussing on the major parts involved.
Commencing my search for replacement parts I initially concentrated on the fuel regulator motor and MAF sensor. Australian dealer prices for each were incredible – $1200 for a regulator motor and around $300 for the MAF sensor. Armed with the correct OEM part numbers I started searching for these parts on the Internet. A genuine regulator motor was soured from the UK for less than $200 landed in Australia and a non-genuine MAF sensor from China for around $40.

The MAF sensor was fitted and appeared to solve the problem for several months. The replacement fuel regulator was also fitted. However, I felt the latter was emitting a strange whine whist operating and I was not happy with the noise. The APF problem was not solved and persisted for a few more months. During that time I noted a forum post by a person who appeared to have an intimate knowledge about APFs. The quote was “that in my experience such faults always seem to be related to the operation of the fuel regulator.”
I noticed that there was a fuel regulator repair kit available from the UK. It consisted of a new metal gasket, an “O” ring and split spacer which replaced parts on the shaft of the regulator motor. Reasonably priced, I ordered several kits. After fitting the repair kit to my old regulator motor and reinstalling it on the high pressure fuel pump I tentatively started the engine. The change was immediate – the APF was not registered on the dash and the engine was operating normally again.

A lengthy test run indicated that the motor was running like new – the power and the torque of the HDi engine had returned along with much improved fuel economy. Fuel consumption over the past 2 months has now returned to 5.2 litres/100km on the M1 from Morwell to Melbourne.
Looking back at the problem it became obvious that the small “O” ring had worn and allowed excess fuel to enter the common rail, trigger the SPF and cause the engine to run on. It was also probable that the MAF sensor required replacement
Although the problem took some time to sort out, it seemed to be a fairly simple solution to the APF in the end.




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