Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics

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Sat 1 Aug 2015 11:37
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - NotanAstraMasta
Hi all I'm fairly clueless when it comes to cars but I have an idea about how things work.
That being said my engine light remains on, on the dashboard and I know that without running a diagnostics on it I can't tell what's wrong. I've heard there is a method of getting the fault code yourself if this is true can some one please explain or refer me to a place where I can learn how to do this? I don't have £50 to spend on getting this done.

Thanks in Advance

M
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Sat 1 Aug 2015 11:57
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - elekie&a/c doctor
It depends how many pins you have in the diagnostic socket.Are there 10 or 16 pins?
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Sat 1 Aug 2015 12:14
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - NotanAstraMasta
There are 16 pins in my socket mate
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Sat 1 Aug 2015 13:10
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - elekie&a/c doctor
So you have the 16 pin obd socket.Don,t think you can do paper clip test on these.It is only for older models.You can buy a cheap obd reader for £30 or less,which should do the job,if it is a petrol model.If it is a diesel,you are going to need much more expensive equipt,or take it to a garage.
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Sat 1 Aug 2015 13:10
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - NotanAstraMasta
It's ok I found out it doesn't work for my model I have a missing pin so it needs to be hooked up to a fault reader :/ I'll have to get saving
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Sat 1 Aug 2015 13:52
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - Railroad.
If you have a 16 pin connector bridge terminals 5&6. Just to be safe use a fuse. Switch on the ignition and the MIL will blink, displaying the four digit code. Count the blinks for each digit ie. 0105 - ten blinks, one blink, ten blinks, five blinks. Each code will be repeated before displaying the next one (if any). I used to work in a Vauxhall dealership and it's a while since I've done this. I cannot remember the code for No Fault Found. You'll have to google it.
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Sat 1 Aug 2015 16:13
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - NotanAstraMasta
Thanks guys I established it is not the right model to be able to bridge the pins so as suggested I think I need to order an OBD II Tool. Does anyone know if all types work with any car? It is a petrol thankfully,
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Sat 1 Aug 2015 19:54
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - hardway

Even supposing you go the buy a code reader route it's still possible to get it wrong.

Pulling up a code for say the o2 sensor fault does not mean renew that sensor!

Many other codes could lead you down the road of a pile of new parts and still the EML is on!

The web is full of people who bought code readers and then replaced parts to no better running,

Codes stored are ONLY a guide to what the cars ECU is "seeing".

Not a list of actual faults.

The £50 pounds you quote isn't for just plugging in a scanner it's also for the experience and knowledge to say "this is the fault"

.though even mechanics have been known to be wrong!

But if you insist,

Buy a scan tool,

I'd say get a dealer quality clone from Ebay like" Vauxhall OpCom."

assuming you have acess to a laptop.

load it then read the codes,

THEN research on the web for interpratations of those codes and possible causes.

DO NOT BUY PARTS ON THE BASIS OF WHAT THE SCANNER READS.

Of course it may be that your scanner says intermitent miss fire cyls 2/3,

then despite all I've written that does usually mean replace the coil pack,

Very common on these.

Sometimes a cigar is just a cigar.

Or you could try a reccomended small garage,

I certainly do not charge that for a basic scan on a common car!

I'm sure others do the same as me.

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Sat 1 Aug 2015 23:44
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - Railroad.
Diagnostic Trouble Codes (DTCs) fall into two categories.
1. Circuit faults. Where a component or wiring is open or short circuit.
2. Mechanical faults that are having an effect which is being detected by a sensor. This does not mean that the sensor is necessarily at fault, as quite correctly detailed by the above poster.
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Sun 2 Aug 2015 10:45
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - NotanAstraMasta

Hardway and Railroad thank you for the advice it's very helpful and it's a fair point that you pay for the experience of a mechanic / auto electrician I just thought if it was something simple like a sensor malfunction it would save me a couple of much needed pounds in the long run. I would take it to a garage to have the work carried out anywayI just didnt want to be pinned against a wall to get the work done straight away (athough potentilly urgent) I am about 3 weeks away from pay day so I will unfort have to wait and potentially find other means of transport until them. I had a coild pack go on me in my previous car (a Ford Fiesta 2003) and It doesnt feel the same as that - not that I know what I'm looking for. Tbh I think shes due a service anyway as with all things it happens at the best possible time!

Thanks all for your help I feel I've learnt a little anyway

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Sun 2 Aug 2015 22:15
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - Railroad.
Buy a code reader by all means, and post here the fault codes on your car.

Think of it this way. If you shoved a potato up the exhaust tailpipe the engine would at best lack power, or at worst not run at all due to the back pressure. Let's say a fault code results. What code could be stored?

Well to begin with a blocked exhaust would have an effect on manifold vacuum, and so a MAP sensor code could be stored. So could a code relating to the O2 sensor. Replacing these components will not solve the problem because we know what the problem is. Some idiot stuffed a potato up the exhaust. The ECM though has no way of knowing that.

I hope I'm making myself clear.
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Mon 3 Aug 2015 10:37
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - NotanAstraMasta

I'm with you Railroad cheers

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Mon 3 Aug 2015 11:51
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - Railroad.

I agree with Railroad but fortunatley you do not get many pototos up ones exhaust.

No perhaps not, but it's perfectly feasible for an exhaust to become blocked. My point is the ECM cannot think, reason or apply common sense. It's a computer that's programmed to carry out calculations based on input data.

To go back to the example I gave, the ECM has no way of knowing the exhaust is blocked because it can't see it or measure it, but it would receive a low signal from the MAP sensor due to low manifold vacuum, and also possibly the O2 sensor may go out of range. Along would come Mr Tech with his diagnostic scantool and he would see fault codes relating to those components. Unless he did some checks he would probably replace them and then scratch his head and wonder why the fault was still there. It may or may not occur to him that the fault is having an effect which then means the sensors are reporting data that the ECM regards as out of limits. The fault is not with the sensors themselves. That's the point I'm trying to make.

To even stand a chance of finding faults you have to think the way a computer works. That's why the fault codes are a guide, intended to point you in the right direction. The problem is too many people take them as gospel, and that's why so many faults are mis-diagnosed.

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Mon 3 Aug 2015 12:13
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - MrDanno

Exactly Railroad, on the other extreme there are sensors that can fail within what the ECU classes a normal range and no code will be generated.

Personally I find live data is a much better indicator than codes but, that requires a bit of knowledge to decide what the fault is.

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Mon 3 Aug 2015 13:28
Vauxhall Astra F - Vauxhall Astra pedal / paper clip diagnostics - Railroad.
Me too MrDanno. Some of the best information available with a scantool on a petrol engine is short term and long term fuel trim. With the right knowledge this can tell you a lot about the engine and the way it's running.

Sensors generally provide a return voltage to the ECM between 0.5v and 4.5v. Between 0v and 0.5v would flag an open circuit code, and between 4.5v and 5v would flag a short circuit code. These may be interpreted as voltage low or voltage high.

But as you say, a sensor may be reporting within its parameters and still be faulty. No code will be set because the ECM is happy that its return voltage is within limits. Mass Air Flow sensors are good examples of this.
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