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MG ZR ZS ZT Technical - ZR - EMS Code Reader

I have a 2004 ZR160 that has a recurring problem with the Engine management system triggering a warning light.

Every "expert" gives me a different diagnosis, a sensor or other part is replaced, codes cleared, then it goes again after 50- 150km.

I have now decided I need to purchase my own "code reader", and fix it myself. However as a 2004 model sold in Australia, where do I get a code reader & which make/model.

All help & advice greatly appreciated.

Tony
Black Mountain
Australia
A L SLATTERY

Good question. I have a late 2004 ZS 180 and it took me a while to find a cheap code reader that would work at all. Also as one of a tiny number of people with a Windows 10 phone there are a limited number of free apps that are compatible. The ones I have tried give some basic information about what the engine is doing, but they show no error codes. I find it difficult to believe that not a single code has been generated in 12 years and 45k miles, and many other engine functions like fuel usage are not displayed either.

Really you need a friendly garage mechanic with one of the more sophisticated professional devices. It may even be worth paying for a report on the error codes, then dealing with the faults yourself, but you may end up paying for repeat reports.

Also remember that the codes are only as good as the software engineers imagination as to what might be the cause of each detected error. In the early days of these systems my daughter's Honda was intermittently not starting and the code indicated a problem with the (single throttle-body) injector. It was nothing to do with the fuel system, it was the main relay.
paulh4

Well the code reader has arrived & tells me there are 2 fault codes present:-

PO420 - Catalyst System Efficiency below threshold Bank 1

PO300 - Random/Multiple cylinder misfire detected

My next step is to "clear" the error codes, & do a test drive and see which error code occurs first. I suspect that the 300 fault is causing the 420 fault.

BTW, the following has already been replaced since the faults started some 18 months ago:-

Fuel Filter
Idle control valve
camshaft position sensor
crankshaft position sensor
catalytic converter
rear exhaust muffler
throttle position sensor
fuel tank removed & cleaned - pump tested ok
coil packs x 2
plug leads
spark plugs
oil & filter change (routine)

Any advice would be very much appreciated.

It is a 1.8 VVC engine.

Cheers

Tony
A L SLATTERY

Which reader did you get?
paulh4

Maxiscan MS509
A L SLATTERY

Thanks. Debating between that and the 309 which is quite a bit cheaper.
paulh4

And whether you buy "genuine" or "replica".

Replicas are way cheaper - have no "serial number" & don't perform all promised functions, but may do all you want - you get what you pay for these days.....

Don't ask me how I know this.....

PS - Google is your friend !.
A L SLATTERY

Indeed. Googling has thrown up the risk of counterfeit items. On the face if it the 509 - for what you can get it down to - is much the better option as there are so many features over and above the 309. But the 309 is so basic - really just code display and reset - that it should either just work or not rather than having problems with the more esoteric features of the 509 ... hopefully!
paulh4

The 509 has been out of production for a few years now, so anyone selling new ones now could be offering "something else", that does not have all the features of the "original" 509. But if the price is right and all you really want is the 309 features, so be it.

BTW - it seems to matter not where the stock is held if you are trying to buy "genuine".
A L SLATTERY

Still trying to fix this car.

After a long highway run 45mins+, it develops a minor/random misfire.

After the MIL activates - the reader finds this error code:- PO420

Can anyone offer any clues what might be wrong - please refer the list of parts already fitted above !.

Thanks in anticipation.....

A L SLATTERY

Have you tried Googling it? Lots of hits for me, expanding on the text on your reader, i.e. a problem with the cat for bank 1.
paulh4

Tony
Does your scanner have the ability to show graphs
If it does you need to get both your oxygen sensors up and go for a drive
To explain how it works,--Your car operates in what is refered to as closed loop when you are under normal driving/cruising conditions---In this mode the PCM monitors the front O2 sensor to calculate the required fuel flow to give the correct mixture for the engine and for proper operation of the cat
Sensor #1 should operate in a wave pattern either side of half a volt like .2v-.8v and do this all the time except when coasting--when it will be lean and around 0
or when accelerating when it will be richer and either show a wave pattern higher up on the graph or even a full 1v reading--------Both these conditions should return to normal as soon as you resume cruise mode
sensor #2 is behind the cat and monitors the operation of the cat---It will start off with a similar wave pattern as the front sensor until the cat warms up and starts working at which time the wave form will flatten out and this sensor will then read a constant 7.5v or 8v in a straight line on the graph
Depending on the cat. on the car warmup time varies a bit but usually by the time you get to the highway and start cruising it will be working
When running down a hill sometimes the cat will cool out and the rear sensor will start to wave again but it should quickly return to normal as soon as you start cruising again

There are a couple of things that could be going on with your car
Number one-- to have that code come up on it's own means the cat. isn't working properly
This can be a faulty sensor-which you can check using the info above or it's a faulty or sports cat. that has been fitted---Was it a genuine cat
A sports aftermarket cat will give all sorts of problems as they take ages to warm up and stop working if you're not in the throttle all the time

If both codes are coming up it's telling you the mixture is out and usually if that random missfire code is there ,then there are only two options
One is that the front O2 sensor is misreading because of heatsoak or failure of some kind which should show up on your graph---- OR
It actually does have a missfire-maybee coil overheating which is fairly common
A missfire will cause a missfire code and also because a missfire causes a lean O2 reading you will get cat monitor code as well
Your scanner should have freeze frame data whic will record the relevant sensor's readings at the time the code was logged
I could go on forever but that should be enough to get you onto it
I'll wait here
willy
William Revit

oops
should be 0.75-0.8v for the rear sensor-----not7.5-8v

sorry about that
William Revit

Thanks Willy, You have given me what I need to move forward on fixing this car & just in time too as it's about to become my daily driver - though I don't go that far these days. Sorry for the delay in reply, only saw your message 10 minutes ago - Cheers

Tony
A L SLATTERY

This thread was discussed between 01/06/2016 and 26/01/2017

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