Technical P0638 & P1687 Stilo wont rev.

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Technical P0638 & P1687 Stilo wont rev.

evil512

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Hi all!

I have a new problem with my Stilo (2003, 1.6 MW).

About a week ago, during engine start it activated the MIL light, and it wont rev.
In neutral it rev'd until ~2500, but in first gear only until about 1800.
And it was running very rough, as only 3 cylinders were working.

After restarting the engine, everything was back to normal, except for the MIL light.

When I got home, I read and deleted the codes:
P0638 - Throttle Actuator (1)
P1687 - Electrically actuated throttle (learn stop)
P0136 - O2 Sensor (7) ( I dont think, this is relevant.)

I have cleaned, the throttle body, but the error codes are comming back regurarly.
At about every third engine start I have this problem.

Had someone have this issue?
I want to check the connectors of the throttle body with contact cleaner,
but I dont think, that will solve the problem.
Can it be a D4 Connector issue?

Any help would be appreciated!

Thanks!
 
Lambda Sensor(O2 sensor) costs about £20 on fleabay. Quick easy fix.
http://cgi.ebay.co.uk/LAMBDA-SENSOR-O2-OXYGEN-4-WIRE-FIAT-STILO-/200530725971?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2eb0900c53

Do the throttle relearn proceedure, it may cure your other problems.
P0638 - Throttle Actuator (1)
P1687 - Electrically actuated throttle (learn stop)

just key on, don't touch a thing (no pedals!) , after 30 sec. key off , wait 30 sec., ready, throttle position is relearned now!
 
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Lambda Sensor(O2 sensor) costs about £20 on fleabay. Quick easy fix.
...

Thanks for the link. I will get to the lambda sensor, if I have this revving problem solved.

Some updates on that:
I have cleaned the throttle body connector and the d4 connector with contact cleaner, but no change :(
 
Hi!

Could somebody take a look at the graph?
What is the difference between throttle position, and throttle angle?
Should the throttle position change, when I press the throttle pedal?

Can the problem be with the pedal sensor, and not with the throttle body?
 

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I don't understand why your throttle position is showing flat line at 7 degrees all the way through

Is it the software? I don't know, it certainly isn't right

For the rest of the graph the rpm is following throttle angle so that's ok

Back to your problem P1687 then you need to investigate the wires and connectors from throttle body connector itself to the ECU. Sometimes it's the ECU itself not putting out the 5v ref voltage to the TB because of an internal connection fault. Your car is cerainly in limp mode to save engine damage as the ECU can't work out where the throttle actually is from the throttle position sensor
 
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Hi Deckchair5! Thanks for the answer!

I don't understand why your throttle position is showing flat line at 7 degrees all the way through

Is it the software? I don't know, it certainly isn't right

After restarting the engine it is not anymore flat. It is following the throttle angle.

For the rest of the graph the rpm is following throttle angle so that's ok

But the rpm goes only until 2300 rpm, at 100% throttle angle.
That's definitely not ok.


Back to your problem P1687 then you need to investigate the wires and connectors from throttle body connector itself to the ECU. Sometimes it's the ECU itself not putting out the 5v ref voltage to the TB because of an internal connection fault. Your car is cerainly in limp mode to save engine damage as the ECU can't work out where the throttle actually is from the throttle position sensor

I have checked the TB connector. I dont know, what I could do with the wires. As this problem is sporadic, and comes only on engine starts.
I will have to take the car to an electrician...
 
But the rpm goes only until 2300 rpm, at 100% throttle angle.
That's definitely not ok.

As I said, "Your car is certainly in limp mode to save engine damage as the ECU can't work out where the throttle actually is from the throttle position sensor"

If it wasn't in limp mode it might accelerate/decelerate uncontrollably without any driver input. Limp mode is just to allow you to get home and get it fixed
 
Hello,

I have the same problem. Could it be the engine temp sensor, because the car goes into Limp mode only when I start the car and the engine is cold. If I let it run for a few seconds and I restart everything is fine, until the next day :). I always get P1220 and sometimes 1687.
 
Unfortunately I need to resurrect this old thread. I read through all the similar threads on the forum, even the ones concerning diesels but unfortunately most didn’t end up with a solution.

So after more than 7 years of faithful service as of lately I get an intermittent P0638 error on my 1.6 Stilo. Car then goes into limp mode – rpm rises only up to 2000/2500 rpm with the acc. pedal fully pressed and engine runs unevenly.

After I restart the engine the error is still there but the car runs fine, accelerates normally and the MIL light is illuminated. After a while with MIL on it again loses the throttle position or something and again starts running unevenly (like on 3 cylinders) and I have to again restart.

After I clear the error car’s back to normal, starts with ‘Check OK’ and everything… until next time.

It now occurs quite often; actually almost always I let it idle or stop at a junction. Before that it occurred on a weekly basis and now the car is getting more or less undrivable having to restart it every time I stop and pull out.

The error occurs ONLY when the car idles and rpm is around the 1000/1500 revs mark. Never occurs while starting it cold or while starting in general actually. That means at the traffic lights, while parking etc. It never goes into limp mode while at speed with a gear engaged regardless of acc. pedal position. Also occurs no matter whether the brake or clutch is applied.

So here’s what I’ve tried so far:

1) Clean engine fuse box with a whole can of contact cleaner:
08052014599.jpeg
08052014601.jpeg
2) Clean D4 connector and fuse box connectors in engine battery tray:
08052014602.jpeg
3) Clean throttle pedal connector:
25042014536.jpeg
4) Clean throttle body connector, TPS and the whole interior of the TB:
08052014587.jpeg
08052014589.jpeg
08052014591.jpeg
08052014597.jpeg
5) Resolder some pins on both 'A' and 'B' side connectors of the ECU as they seemed to have fallen through:
P5061495.jpeg
P5061496.jpeg
Resoldering the pins was actually my best guess as you can see in that picture this pin nr. 57 (connector B) was quite loose and sunken through the pcb and as the guide for the ecu pinout here states pin 57 on connector B is responsible for ‘57 DBW motor positive (motorized throttle)’. Unfortunately it is not connected to anything - there’s just a placeholder on the connector on that spot:
07052014581.jpeg
There are no other P error codes accompanying the 0638 error. But after checking the ECU errors with FES I also got the U1602 of which the description states something like CAN bus comm. – the body computer and ECU lost communication at some point;

I am attaching a log of throttle angle, rpm, manifold pressure. I've highlighted the weird point in red (rows 308, 309, 324) where throttle valve angle drops to 0%; accoring to my diagnostic the error occured at 8:47 but I don't notice anything abnormal there:
View attachment OBD_log_20140507.zip


So any advice here would be very highly appreciated. Next on my list is changing the throttle body with a second hand one and changing the acc. pedal with a geniuine new one. Parts are due to arrive today, so I hope to report back with some progress soon.
 

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I had two pins dropped on ecu and the thick purple white trace cable in the d4 connector is like a bow string and when placed on it's locating peg it kept pulling it back enough to annoy me. Move the ecu from off the engine
 
So, where was the problem ?? i've same issue from couple weeks

This thread is 3 years old and chances are the OP isn't around anymore to answer.

That said; looking at the pictures posted above it's quite clear the ECU has several burned pins on the circuit board, a problem the 1.6 is well known for having.

Usual advice is to fix the burned pins. It can be done DIY if you're confident with a soldering iron or there are professional ECU repair services out there that will do it too.

This chap talks through repairing burned pins on the ECU here:



Then good advice is often to relocate the ECU away from on top of the engine where it won't be subjected to the same amount of heat soak (which is the cause of the burned pins in the first place).
 
Still here. Sorry for not concluding this thread on time. As you all already know this is a common issue with the 1.6 ECU. It gets too hot, being bolted onto the cylinder head and a BGA chip de-solders and you get all kind of weird errors depending on which pin (ball) has been cracked. There's tons of info on the internet.

Re-soldering the connector pins usually has no effect as the chip is faulty in most of the cases.

There are two ways to fix this:
1) Give it to a specialist who would perform the BGA reballing procedure
2) Buy a new or "virginized" second hand ecu ecu. Although they are in scarce supply these days and cost a lot.

I eventually ended up with option 2). I bought a used virgin ecu for about 170 pounds off ebay. Car doesn't go the same anymore, I'd say, the engine judders when the gas pedal is released, but besides that runs and drives as before.... 14 years already, 11 in possession.

And most importantly: move the ecu off the cylinder head!
 
Hi,
Many thanks for reply this old post :)

I've cleaned ecu all inside, repleaced one driver MC33186DH1, also i'd resoldered pins and improved other circuits in ECU (BEFORE on left, AFTER on right).

Many thanks for reply this old post :)

For now, it seems there is ok. no error or other symtops from 3 days.

Two years ago, after first ECU regeneration , I moved ECU between the battery and the engine but it was still warming up, but not that much as at original place. On saturday i need to move ECU to left side battery cover.
 

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