HDi TPS repair guide (Throttle Position Sensor)

[DeeTurbo]

Over the 13 years and 300k miles of owning my 306 HDI one fault has cropped up time after time and that's P0121.

After the last time the prices had gone up now up from £70 to £134 for a new one from the dealers I thought I'd have a look at trying to fix it as it's just getting to pricey to replace all the time. The shortest time ones lasted is just over a year! I've tried the earth mod that some other forum suggest to no avail.

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I have now found the real reason why my TPS was playing up and it will most likely to be the same on yours to. I use to think it was contaminated grease in the unit but it is the female connector on the plug that is to blame.

The reason why my other guide worked is because of the same reason why the wiper track clean guide works, the action of removing the plug disturbs the corrosion and does clean the contacts a little.

Even though the plugs are sealed they only have rubber gasket type seals and the angle that the TPS sits at the front of the bay lets water off the roads to sit in little puddles on the end of the connector. This water slowly makes its way in to the plug and the terminals will corrode with this moisture.

It's very difficult to see the corrosion in the plug but it's there.


The reason I found out was I bought a new TPS and I got the fault again the next day and thought I'd investigate further.

You can see here where the water will sit and get past the rubber seals.


Take the plug off and clean the terminals on the TPS.


To clean the female contacts you will need to insert something with an edge, I used a paper clip.


After cleaning the terminals I stuck some silicone on the top of the plug. Make sure you don't have any gaps and make sure you get between the cables.


Since doing the above I put the old TPS on and it has been fine for the last 6 months.

So clean the connectors on sensors or other bits that have gone wrong before changing them. I did the same on the wiper motor when that stopped self parking. The wiper motor connector doesn't even have a gasket between the motor and body connectors.

Below is how to change the grease on the TPS if you really want to but I think that is a waste of time.

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All this repair involves is taking the TPS a part, clean out the old grease and replace with new, so very simple.

The first time I did this was over a year ago and I've not done it again since. I'm guessing the clean out has sorted it.

Remove the TPS from the car.



Lay the TPS flat on the bench.



Using a thin flat screw driver pull out the glue out two of the heads of the screws.





Unscrew the screw out to release the sensor from the body of the cable holder. Then unscrew the three torx screws on the sensor module.







Carefully lift out the top. There is a spring behind the top.



Lift out the centre.



Clean off all the grease and in the nooks and on the centre of the body of the centre as well.



Regrease and reassemble.



There is a bit of a knack to get the spring back into position and just be patient.



Replace the three screws.



Reassemble the unit by placing the sensor module back on to the cable body.



Screw the two back together.

Now the unit should work as it should unless there was something else wrong with it. For a free fix this is worth trying before forking out on a new unit.

I've done this guide from memory and I will be taking a spare a part soon so I can add a bit more detail to this thread in the next couple of days.

I hope this help someone out there.

Before starting the car it will be worth using OBD tool to check that the sensor goes through it's range smoothly with out any jumps in the amount of throttle applied.

Good luck and let me know how you get on.