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Forums › The Car › 206 Problems › Diagnostic Results |
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 Posted: Tue Apr 23, 2013 1:09 am |
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Joined: Aug 01, 2011
Posts: 390
Trade Rating: 0
Location: Bath UK
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It's best to tackle recorded faults logically, when the car spots a fault and you can't find it then it generally means the car's on board diagnostics is better than yours  Freeze frame data will tell exactly what and when and under what circumstances the fault occurs and how frequently that happens and it can't lie. The difference is that the car's OBD is monitoring everything for the whole journey which is different from checking things when it's static in a garage
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Posted: Tue Apr 23, 2013 3:48 am |
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Joined: Feb 07, 2010
Posts: 2949
Trade Rating: +6
Location: Athens, Greece
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| Deckchair5 wrote: |
| It's best to tackle recorded faults logically, when the car spots a fault and you can't find it then it generally means the car's on board diagnostics is better than yours Freeze frame data will tell exactly what and when and under what circumstances the fault occurs and how frequently that happens and it can't lie. The difference is that the car's OBD is monitoring everything for the whole journey which is different from checking things when it's static in a garage |
Yes, it can and does regularly. 
OBD is not a perfect system (esp. on a 206) and in no way should it be taken as 100% correct all the time.
Very often what appears as a certain or multiple faults, will have to do with something completely un-obvious related to the DTC given.
It's meant to assist in diagnosis, but in no way replace human evaluation and fault-finding.. yet.
I'm sure you agree with this and know already what I'm trying to say, and the OP should definately make the checks you point-out (if he's still around).
However, in my experience valve tappet adjustment should be absolutely mandatory on the TU3 every 25.000 miles or if you have engine-running related issues like the OP.
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| 1.4i, 2001, 3-door, China Blue
Repair safely - Drive safely | |
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Posted: Tue Apr 23, 2013 6:27 am |
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Joined: Aug 01, 2011
Posts: 390
Trade Rating: 0
Location: Bath UK
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No, you're quite wrong there. Freeze frame data cannot lie, it can't invent the data. That's what actually occurred and it's the reason why the OBD has triggered a fault
I'll agree with you that how the OBD interprets that data into a suggested fault code can be mystifying (but that's the fault of the programmer) and how the technician interprets that fault code is also open to errors (and that's the fault of the technician) but the OBD is telling you exactly what happened in the freeze frame data to make it record a fault and makes a best guess suggestion as to which system needs further investigation
Often we'll see someone see a fault code and then immediately just change a component and wonder why that didn't work, even some garages seem to adopt this strategy too, at the customer's expense But really the fault code is a suggestion of where to look deeper and then it's up to the technician to make an informed decision after further investigations
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Posted: Tue Apr 23, 2013 11:51 am |
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Joined: Feb 07, 2010
Posts: 2949
Trade Rating: +6
Location: Athens, Greece
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| Deckchair5 wrote: |
| No, you're quite wrong there. |
Where?
| Deckchair5 wrote: |
Freeze frame data cannot lie, it can't invent the data. That's what actually occurred and it's the reason why the OBD has triggered a fault.
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With all respect it can. Esp. with clone interface and even IF it has the parameter in question available in real-time, you interpreting it is one thing and the ECU flagging DTC's from reading it is quite another.
I won't even start on PP2000 itself..
Bear in-mind 206 ECU's are riddled with bugs/errors which if you're lucky might get covered in an update, if you actually perform the update.
You are also assuming that the ECU's measuring components (ADC/DAC etc) are as good as brand new. In a hot engine bay after 10 or 15 years they drift/fail and that's why there are companies that do overhauls due to wear/faults on them like BBA reman etc. To be expected really as they don't exactly put mil-spec components in there.
Most importantly, a lot of data on these systems is 'derived' ie not every single line, voltage, current flow is sampled for diagnostic purposes. (Some might, but I don't believe it's the case with the 206)
A lot of the time a DTC relating to a specific part will come-up based on combinations of readings from other parts of the engine etc.
So even a DTC to do with the λ-sensor heater circuit (which should be very straightforward for the ECU to get right) can sometimes be due to unrelated issues and I have indeed had this exact code on my 1.4i 2001 when the heater circuit was 100% perfect, even after a brand new OEM sensor (and other parts) were changed/checked "just in case" - with a 'scope.
I fully agree, replacing parts just on the basis of a DTC, sometimes, might, only fix the symptom temporarily instead of getting to the root cause of the problem as you say.
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| 1.4i, 2001, 3-door, China Blue
Repair safely - Drive safely | |
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Posted: Tue Apr 23, 2013 1:55 pm |
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Joined: Aug 01, 2011
Posts: 390
Trade Rating: 0
Location: Bath UK
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Ha! We are going around in circles here
I said
"Freeze frame data cannot lie, it can't invent the data. That's what actually occurred and it's the reason why the OBD has triggered a fault".
A clone interface or even PP2000 has nothing to do with the freeze frame data stored. Whether the engine sensors are tired or hot makes no difference, the freeze frame data tells you WHY the fault code was triggered and it can't invent the data. If the data is inaccurate then it will trigger on that inaccurate data but it can't invent it and cannot lie that it happened if it didn't. An ECU will sit there for ever and never issue a fault code, until the data exceeds certain set parameters
As I said before, a fault code is a best guess interpretation of the data triggers and shows the suggested area for investigation and that's no different than you looking at the data and making an informed interpretation of the data
Example
You have a P0135 DTC and APF warning as in this case. You look at the O2 heater and check out the O2 sensor for continuity and supply and ground and everything seems fine. But what else is on that circuit? You check out the wiring diagram. The electric purge cannister has the same feed. Could a problem there cause a problem on that circuit and trigger both those warnings? Well what do you think?
So the fault code points you in a direction for further investigations. The OBD is doing the best it can and warning of a problem with the anti pollution system and stating there is a fault on the O2 sensor heater circuit but then you have do the checking. Someone can say "I even changed the 02 sensor and it's still saying the same heater circuit problem." Well, yes, it will do
The P0135 fault is an electrical CIRCUIT problem and so needs further investigation on that electrical circuit
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Posted: Tue Apr 23, 2013 3:29 pm |
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Joined: Feb 07, 2010
Posts: 2949
Trade Rating: +6
Location: Athens, Greece
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| Deckchair5 wrote: |
Ha! We are going around in circles here
I said
"Freeze frame data cannot lie, it can't invent the data. That's what actually occurred and it's the reason why the OBD has triggered a fault".
A clone interface or even PP2000 has nothing to do with the freeze frame data stored. Whether the engine sensors are tired or hot makes no difference, the freeze frame data tells you WHY the fault code was triggered and it can't invent the data. If the data is inaccurate then it will trigger on that inaccurate data but it can't invent it and cannot lie that it happened if it didn't. An ECU will sit there for ever and never issue a fault code, until the data exceeds certain set parameters
As I said before, a fault code is a best guess interpretation of the data triggers and shows the suggested area for investigation and that's no different than you looking at the data and making an informed interpretation of the data
Example
You have a P0135 DTC and APF warning as in this case. You look at the O2 heater and check out the O2 sensor for continuity and supply and ground and everything seems fine. But what else is on that circuit? You check out the wiring diagram. The electric purge cannister has the same feed. Could a problem there cause a problem on that circuit and trigger both those warnings?
So the fault code points you in a direction for further investigations. The OBD is doing the best it can and warning of a problem with the anti pollution system and stating there is a fault on the O2 sensor heater circuit but then you have do the checking. Someone can say "I even changed the 02 sensor and it's still saying the same heater circuit problem." Well, yes, it will do
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Agree with all of the above but I was refering to ECU components not sensors, being heated/failing.
| Deckchair5 wrote: |
The P0135 fault is an electrical CIRCUIT problem and so needs further investigation on that electrical circuit |
Exactly. That was my thought when trying to solve it as you'd think it's not a difficult issue with eg. mixture, misfiring, and all that.
Heater line could be could only be:
1) Open circuit
2) Short to ground
3) Short to +ve
4) Inadequate current flow (eg. worn heater resistor or simillar)
/Interminent or continious.
However, as you point out the +ve feed for the heater comes from the relay beneath the ECU which also supplies Purge canister, the other λ-sensor heater, and the fuel pump if I mind. So if say relay contacts are so inclined with the highish currents involved and all these turning on and off, the ECU can percieve a problem with the heater of the sensor (on mine being the most far away in the loom I should add) while the other said lines fall within tolerance limits.
I'm generalising obviously to make a point but I think we agree essentialy and maybe I didn't say things too well, and drifted a bit.
P.S. Problem went away when I binned the old ECU as other problems were appearing and it was the wrong type for a 206 anyway.
A technician at a Peugeot dealership had replaced it with that of a Partner Van (KFW) sometime in 2003, long before I bought the car. He logged "Updated ECU" in the guarantee file. 
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| 1.4i, 2001, 3-door, China Blue
Repair safely - Drive safely | |
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Posted: Wed Apr 24, 2013 2:58 am |
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Joined: Aug 01, 2011
Posts: 390
Trade Rating: 0
Location: Bath UK
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Problem went away when I binned the old ECU as other problems were appearing and it was the wrong type for a 206 anyway.
A technician at a Peugeot dealership had replaced it with that of a Partner Van (KFW) sometime in 2003, long before I bought the car. He logged "Updated ECU" in the guarantee file
Ha! Well that was nice if them! One would hope that they checked it was compatible before fitting
But there you go, a problem with the O2 heater sensor circuit could just as easily be the ECU as it's obviously a part of that circuit
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Posted: Thu Apr 25, 2013 5:12 am |
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Joined: Apr 03, 2013
Posts: 58
Trade Rating: 0
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Hey, I will get round to checking all the points raised soon. I reset it again and the codes haven't come back since but the revs are still hanging. There doesn't seem to be a lack of power anymore though.
There is 50,000 miles on the clock.
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Posted: Thu Apr 25, 2013 9:41 am |
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Joined: Aug 04, 2011
Posts: 1343
Trade Rating: 0
Location: Swindon
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One problem that people often forget is that the modern engine management systems are "feedback" circuits that correct for suspected faults so they can lie - well sort of.
I always think of the following as the best example:-
An exhaust leak (however slight) before the first lambda will allow air which includes 02 into the exhaust system. The lambda will "see" the excess O2 and feed the signal back to the ECU which will then richen up the mixture to compensate for what appears to be lean running. Ultimately the extra fuel will then destroy the lambda sensor and your CAT as neither will withstand that extra fuel.
That is only one of many types of fault that your sensors will "see" and the ECU will then attempt to correct for when the fault is something entirely different.
So while the systems don't strictly lie they can be fooled and the sensor outputs, while correct, are for the wrong assumed cause. So the morale of the story is to be very careful and check all other parts of the system before assuming that the readings and the effect are genuine reflection of root cause.
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| Morris 1000, Austin 1100, Escort Mk2, Fiat Mirafiori, Alfa 33, Alfa GT Junior, Alfasud, Alfetta GTV (2x), Alfa 164 3.0 V6, Alfa 164 2.0, Alfa 75 V6, Alfa 156 2.4 (diesel remapped 200bhp), Alfa 147 GTA (3.6 295bhp), Alfa 159 (diesel remapped 245bhp 300ft.lbs @ 2500rpm)
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