Independent Renault Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter #1
Would anybody know how I can test that the TDC sensor on my Scenic 1.6 16V is working? What is the output?

I am suffering hot starting problems. Would the temperature sensor be at fault? The temperature guage seems to be fine. Is there another engine temperature sensor for the ECU other than the guage sensor?
 

·
Premium Member
Joined
·
4,285 Posts
What are your symptons? If it's erratic then I would say it's your TDC. It's a simple and cheap fix so I recommend that you change this first and see how you go.
 

·
Registered
Joined
·
2 Posts
Discussion Starter #4
Thanks for all that info. Very useful.

What I cannot understand is why this sensor seems to show its symptoms only when restarting from hot??

If this sensor was faulty, why does it not have problems when cold and even running?

Is this sensor only used when starting the engine??

Thanks again
 

·
Registered
Joined
·
63 Posts
tdc kangoo dci

I suspect it is because it is a magnet, and magnets loose strength when hot...
but can anyone tell me what readings one should get with a volt meter... should it have a resistance? or should it test as a diode?
I have one in my hand and it has a capacitance of 10uf but nothing else.... is this right?
 

·
Premium Member
Joined
·
43,291 Posts
The TDC sensor consists of a magnet surrounded by a coil and as the metal teeth of the flyheel sensor points pass it a small current is sent to the ECU. The only sure way of testing its operation would be to use an oscilloscope. The reason being that the gap in the flywheel points is when the TDC sensor pulses change and the ECU makes use of this change. The pattern on the scope would be a series of peaks with an obvious gap on each rotation of the engine.
Any form of electrics tends to perform worse as the temp increases. Also check the TDC sensor electrical connections which if poor will also perform worse when hot. If you are satisfied the TDC sensor and its connections are OK it could be the coolant or Air Inlet Temp sensors ar duff.
Give the TDC senor a good clean check its connections and see waht happens therafter:)
 

·
Registered
Joined
·
63 Posts
Thanks for that...
if it is a coil., i would expect to pick up a resistance of a few ohms..,
I get nothing.. except capacitance..
I will put my scope across it and wave some metal passed it and see what happens..
....
ok, I get a kick. but only about 50mv..
I have a replacement on order... but this being Africa.. it is still 2 days away..
I will compare the replacement when it arrives and update...
 

·
Registered
Joined
·
63 Posts
further

A new one tests as a resistive coil of 702 ohms.
I also tested a megane dci and it tested at 670 ohms.
I had to give the chasis number with the order.. apparently although they all look the same.. they are different?
 

·
Registered
Joined
·
63 Posts
more feedback

I replaced the TDC sensor. the new one tests as a 700ohm coil, the original failed to start when hot, then eventually failed. The coil was open circuit. The previous person had removed the plug and soldered the wires directly to the sensor. The plug is apparently not sold separately from the loom, so i did the same, then sealed it with silicon rubber.. The kangoo is now starting and pulling well.. I am concerned that I do not know if the wires may be reversed on the sensor... but replaced them as they came off.
is it not strange that Renault can build F1 racers, but makes a TDC sensor that does appears to be a major weakness.. a magnet with a few turns around it should not be rocket science?
 

·
Premium Member
Joined
·
43,291 Posts
Gret news IVAN - glad to hear you got the TDC issue sorted. When comparing renault cars against their F1 team you have to remember they probably renew the TDC sensor every race and even then they rarely run in the rain.:rofl:

Ye I agree the renault TDC sensor seems below par when it comes to quality but engine electronics have to operate in a quite hostile environment. Apparently Renault have modified the unit and its connecting harness but time will tell if they have been able to make any significant improvement.:)
 

·
Registered
Joined
·
63 Posts
In my case the plug had even been removed and soldered direct.. I would agree that the plug should be cleaned.. as a first option.. but it seems there must have been an assembly weakness which causes the coil to go open when hot and come right as it cools.. Perhaps only Renault could get that right? I have heard of no other make who apparently go thro TDCs as Renaults do, as reported on this forum..
 
1 - 12 of 12 Posts
Top