OBDII Scan / Source of Engine Light Fault

Forums › Transport (cars, bikes and boats) › OBDII Scan / Source of Engine Light Fault

jasonwaiheke

277 posts

Ultimate Geek

#233370 13-Apr-2018 13:38

My engine light is coming off and on, and I need to find out what it is. Is there anyone who can tell me for free? Or do I have to fork out $$ for a mechanic just to scan it and tell me before I fork out yet more $$ on the repair itself.

FireEngine

1217 posts

Uber Geek

Trusted

#1995493 13-Apr-2018 13:48

If its going on and off as you drive then there are normally only two possibilities:

- Misfire - you should feel the car missing to some degree as well

- O2 sensor(s) - you may feel nothing, certainly not a misfire/stutter, but you may feel some loss of power

Either of these conditions may come and go initially causing the light to turn on/off/on, both will eventually go solid. On a modern car NOT a good idea to leave a misfire, the unburnt fuel can quickly destroy the catalytic converter causing blockage of the exhaust...O2 sensor failure normally causes the car to use a default map. This may give a loss of power, high fuel consumption (or both), but isn't normally bad enough to cause damage to anything expect your wallet...

Maybe post where you are and someone local may be able to help with a scanner, else either Repco or Supercheap can scan it for a small fee.

Regards FireEngine

Lenovo

Lenovo computer and accessories deals (affiliate link).

jasonwaiheke

277 posts

Ultimate Geek

#1995500 13-Apr-2018 14:04

FireEngine:

If its going on and off as you drive then there are normally only two possibilities:

- Misfire - you should feel the car missing to some degree as well

- O2 sensor(s) - you may feel nothing, certainly not a misfire/stutter, but you may feel some loss of power

Either of these conditions may come and go initially causing the light to turn on/off/on, both will eventually go solid. On a modern car NOT a good idea to leave a misfire, the unburnt fuel can quickly destroy the catalytic converter causing blockage of the exhaust...O2 sensor failure normally causes the car to use a default map. This may give a loss of power, high fuel consumption (or both), but isn't normally bad enough to cause damage to anything expect your wallet...

Maybe post where you are and someone local may be able to help with a scanner, else either Repco or Supercheap can scan it for a small fee.

Thanks, I don't feel any misfire, and if it is the O2 sensor I will be annoyed as it was replaced not long ago when the light came on once before.

FireEngine

1217 posts

Uber Geek

Trusted

#1995508 13-Apr-2018 14:08

jasonwaiheke:

Thanks, I don't feel any misfire, and if it is the O2 sensor I will be annoyed as it was replaced not long ago when the light came on once before.

You probably have at least 2 (before and after the cat), or 3-4 on a V engine.

Regards FireEngine

jasonwaiheke

277 posts

Ultimate Geek

#1995533 13-Apr-2018 14:40

Thanks!

So does anyone have a source that can help me out in the Kapiti Coast area?

Blurtie

432 posts

Ultimate Geek

#1995597 13-Apr-2018 15:58

Have you thought about getting a bluetooth OBDII scanner from Aliexpress or here? They're quite cheap, but I can't verify that you'll get the info you're after..

Also, before taking your car to the rip off mechanics, you should check out SupercheapAuto. I know they have the diagnostic gear you're after and do it for a reasonable price. But I've never used them tho.

Edit: fixed link

clevedon

1059 posts

Uber Geek

#1995608 13-Apr-2018 16:26

Blurtie:

Have you thought about getting a bluetooth OBDII scanner from Aliexpress or here? They're quite cheap, but I can't verify that you'll get the info you're after..

Also, before taking your car to the rip off mechanics, you should check out SupercheapAuto. I know they have the diagnostic gear you're after and do it for a reasonable price. But I've never used them tho.

Edit: fixed link

So what occupation are you in by the way?

Aredwood

3885 posts

Uber Geek

#1995691 13-Apr-2018 19:04

Speculating due to not having any idea what make or model of car. Fault is a split in the air intake pipe after the air flow meter.

Ask whoever you go to wether their diagnostic gear supports full factory level diagnostics on your car. If they can't- find somewhere else. As those cheap scanners from aliexpress and elsewhere only give you emissions related codes. Which can often be wrong.

And don't blindly replace whatever the codes tell you to replace. Make sure that the part is actually broken first.

k1w1k1d

1190 posts

Uber Geek

#1995694 13-Apr-2018 19:14

"....before taking your car to the rip off mechanics..."

Most mechanics, like every other trade or profession, are not rip off agents.

Take the car to a reputable mechanic or auto electrician for a diagnosis.

They will charge you for this service. Diagnostic equipment is not cheap, staff need a reasonable wage, and the boss needs to make a profit.

Blurtie

432 posts

Ultimate Geek

#1995726 13-Apr-2018 20:24

Sure maybe that comment was a bit harsh, of course not all mechanics are rip offs. Guess it's just the perception of the test simply involving hooking a machine up to a car and reading some codes. Yes, i'm sure you'll still need skill/knowledge to analyse the codes in order to diagnose the issue; but I don't see the harm in the OP in attempting to run the diagnostic part himself for a relatively small cost (rather than taking it into a mechanic).

Maybe it's just me, but if there was a problem with a device, car, whatever - I would want to try and find out the extent of problem first before going off to the professionals. My comment was directed to the OP at trying to do this. I did not suggest at any point what the issue was/how to fix it, or whether he find the answers he was after with my suggestions. But I still thought it would be worth a shot for $30.

FWIW - I took my car in for a diagnostic test and got charged $150 on the spot just for the pleasure. Suggested repair bill of over 750 (parts + labour). Did some googling, found same parts for around 250 and repair looked pretty straight forward (practically straight swaps for components) so I did it myself. Car still runs fine. If I had known about Supercheap Auto doing similar testing for only $30, I would've jumped at that and could've saved even more. Guess I'm still bitter about it!

Aredwood

3885 posts

Uber Geek

#1995781 13-Apr-2018 22:38

Blurtie:

Sure maybe that comment was a bit harsh, of course not all mechanics are rip offs. Guess it's just the perception of the test simply involving hooking a machine up to a car and reading some codes. Yes, i'm sure you'll still need skill/knowledge to analyse the codes in order to diagnose the issue; but I don't see the harm in the OP in attempting to run the diagnostic part himself for a relatively small cost (rather than taking it into a mechanic).

Maybe it's just me, but if there was a problem with a device, car, whatever - I would want to try and find out the extent of problem first before going off to the professionals. My comment was directed to the OP at trying to do this. I did not suggest at any point what the issue was/how to fix it, or whether he find the answers he was after with my suggestions. But I still thought it would be worth a shot for $30.

FWIW - I took my car in for a diagnostic test and got charged $150 on the spot just for the pleasure. Suggested repair bill of over 750 (parts + labour). Did some googling, found same parts for around 250 and repair looked pretty straight forward (practically straight swaps for components) so I did it myself. Car still runs fine. If I had known about Supercheap Auto doing similar testing for only $30, I would've jumped at that and could've saved even more. Guess I'm still bitter about it!

Some mechanics have a policy of only using genuine parts purchased from the dealer for your brand of car. As good luck trying to get that Aliexpress seller in China to pay for a new engine. Because that waterpump or cambelt that you bought from them failed earlier than expected.

Sure, that makes the job more expensive. But it vastly reduces the CGA exposure of that mechanic.

And I still think that that $150 was good value. As it meant that you could confidently spend that $250, knowing that it definitely would fix your car.

k1w1k1d

1190 posts

Uber Geek

#1995861 14-Apr-2018 07:23

Just an observation on getting a diagnosis done by someone and then taking it elsewhere for repairs.

When I start work on a customer's equipment I will always do a full diagnostic test to confirm the information I have been given.

Getting a diagnosis by Supercheap is probably ok if you want to do the repairs yourself, but not sure that many mechanics would rip into the repair without testing the vehicle first?

richms

26394 posts

Uber Geek

Trusted

Subscriber

#1995894 14-Apr-2018 08:55

Another vote againt diagnostic software on a cheap dongle. They are generally made by people without knowledge of the car, what ECUs and other control units are in them, how they are connected etc.

If you have a car that is commonly sold in asia like a BMW or merc then you have good luck with them, On a japanese region specific toyota you will be lucky to see some engine codes and perhaps reset the airbag and ABS warnings since that is all that most people care about with diagnostics.

You may find hacked versions of the real software around the place with a form of credits added, where you have to pay for each use to the russians that did the software. It may still not work.

Richard rich.ms

Sidestep

1003 posts

Uber Geek

Lifetime subscriber

#1995931 14-Apr-2018 10:14

jasonwaiheke:

My engine light is coming off and on, and I need to find out what it is. Is there anyone who can tell me for free? Or do I have to fork out $$ for a mechanic just to scan it and tell me before I fork out yet more $$ on the repair itself.

At the most basic level many cars have a 'roadside' self-diagnostic option. On my old Subarus it involves connecting two plastic plugs in the wiring loom under the steering column.
On other brands it may involve jumping two pins on the OBD connector or holding in the trip reset while switching the ignition on & off.

The code usually flashes out on the dash or check engine lights, Google tells you what general area the code's associated with.

The next level is those code readers. Plugged in to the OBD they may perform some simple diagnostics, stored codes show on screen, usually with a basic explanation.

Assuming you understand your car's systems this will give you a clue about where the fault might be, allow you to look for broken wires, use a multi tester and manually check sensors etc, clear the codes.

Unless it's something that obvious, your mechanic's professional scanner is where you really need to be.

It'll be able to see the feed from sensors in real time measuring their output more accurately than a simple fault/no fault situation, tell you if the sensor's are reading where they should be under fixed conditions such as a certain rpm, temp etc.

I recently had to replace a couple of sensors that hadn't 'failed' ..hadn't reached the stage where they'd register a fault, yet cause the vehicle to run badly.
The codes it was throwing were for issues that - at first - didn't appear related to faults we diagnosed in the end (via a professional scan machine).

Would have spent a lot of time chasing red herrings otherwise.