Technical Stilo fault codes 1684 1687 1220

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Technical Stilo fault codes 1684 1687 1220

Stilo02dynamic16V

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Hi All,

Can anyone help - my 02 plate 1.6 16V stilo dynamic has fault codes 1684, 1687, 1220 and is in limphome mode. The throttle body has been replaced but made no difference - any ideas? :bang:

Many thanks
 
Have looked through tech section and they suggest throttle body replacement-have done this but car won't do throttle re-learn procedure. Car currently in dealer and they have no idea what the problem is!! Any suggestions?
 
The car developed this fault as we approached a roundabout, came up with engine fault codes 1684 and 1687, limped home, tried a throttle reset then comes up with 1220 throttle relearn fault. Would it be the ECU that failed as we were driving?
 
Could it be anything to do with the aircon pressure sensor circuit, as doesn't this pull the same voltage as the throttle potentiometer?
 
have you searched tech section,this has been covered (including AC sensor connector corrosion) although I have seen throttle bodys been changed in most cases its the ECU. (check voltage at throttle body)
 
I had a P1687 the other day. "Metering oil pump" = the throttle valve really.
As you can guess, it means the ECU is having trouble understanding the feedback from the TPS (the throttle position sensors) so it will go into limp mode to safeguard the engine. In my case, it was the aircon linear pressure switch which is fed from the same 5v supply, (my fault as I was playing with the air con at the time). Mine was easy to sort out but it shows that a problem on the linear pressure switch can throw out the throttle body circuit too

Anyway, the system is like this
throttle body schematic 1.JPG
The ECM is your ECU

Your throttle body has two resistance pots or tracks inside which provide feedback voltage to the ECU to tell it where it is. They're different voltage ranges so it can very accurately determine just where the throttle valve is.

throttle body.JPG
Throttle valve motor and pots
See the two potentiometers here? That's what your ECU is having trouble with.
The outputs from these pots look something like this
trace 1.JPG
This isn't a Stilo but it shows the different voltage feedbacks as a throttle is opened and closed
If someone has a scope then you can trace the feedback voltages from the throttle position pots and see if it's a clean and smooth feedback thoughout the full throttle range with no sudden jumps or spikes

Ok Nodding off yet?

DSC00221.JPG
Now a bad contact here at the throttle body connector would cause your problems so I'd use some contact cleaner (NOT WD40 but proper electrical contact cleaner) on the connector
throttle body connector.JPG


Then I'd get up the other end at the ECU and recheck the connections and some more cleaner there to freshen up the contacts and, of course, check the ECU earths

Again, someone with a scope could check the output voltage from the ECU and what's actually feeding back to the ECU from the TPSs before condemning the ECU. It could well be the ECU that has a problem but it can only go on the information it's given from the throttle body
 
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P1687 means :
"interruption of selflearning (throttle body) due to incorrect environmental conditions / out of tolerance "
so it really has a relationship with the throttle body.

yellowstilo
 
Can the accelerator potentiometer cause the problem? Or the comms between? Also have a cruise control fitted to the steering column connector - which has been working fine.
 
Did you have to put a new linear pressure switch on?
No I just cleared the code and started her up as the problem (me!) was now gone

Can the accelerator potentiometer cause the problem? Or the comms between?
Yes - makes it interesting doesn't it. With TPS fault codes then I suppose the first port of call is there and then work back as the accelerator pots aren't too easy to get to. Two pots in tandem there at the accelerator so it should make it more reliable so I think i'd check the output from the accelerator pots at the ecu and bear in mind they go through the D4 connector- the horror!
 
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Cheers for that Deckchair5(y) - nice to get some answers - dealership are still scratching their heads!
 
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