Picking your next car? Our unique Car Chooser is here to help... | No thanks
2000 1.8 16V - Fault code 0170. - SpamCan61 {P}
Hi Folks;

Well, after about 35K of largely trouble free motoring SWMBO's Zafira decided to play up and light the EML yesterday. Local mechanic read the codes, 0170 'fuel trim malfunction'. Having cleaned up the throttle valve body - 110K miles of gunk was cauisng unstable idle anyway - and reset the light it's currently behaving itself. However I'd like to know what the code really means?

Surely if the long term fuel / air mix is wrong then there should also be the appropriate code for lean / rich mix - 0173 or whatever?

I understand there are all sorts of reasons why the mix could be wrong, principally induction leaks post MAF, the MAF itself, or the lambda sensor, but shouldn't any of these give the too rich / too lean code as appropriate, as well as or instead of the very vague 'malfunction' ?

Thanks for any guidance.

P.S. If it makes any difference it's a 2000 model ( Opel) 1.8 16v petrol drive by wire jobbie, Z18XE engine code I think, Simtec 71? ECU, certainly it needs a proper ODB code reader rather than my trusty paper clip :-((

Edited by Dynamic Dave on 26/01/2008 at 19:40

Tags: technical issues lambda sensors radio codes radio

Fault code 0170 - what's that all about then? - bell boy
vauxhalls seem to light up if you go down a long hill with your foot of the gas,ive had a few do this in the last few years, dammed annoying ,ive checked resistances of throttle bodies and as far as i can tell are in manufacturers spec
Fault code 0170 - what's that all about then? - Number_Cruncher
Fuel trim is more of a long term thing - it's sometimes called an integrator. It is set when there's a consistent error, and, as time passes, the integrator just adds the error up.

It may be worth checking odd things like is the exhaust blocked? Sometimes the stuffing in these exhausts can work loose, and partially block the exhaust.


Fault code 0170 - what's that all about then? - SpamCan61 {P}
Thanks chaps, from my Googling yesterday my understanding is that if the mix is (say) 10% too lean long term then I should get an error code 0171(?) 'system too rich', if the long term mix is rich I should get error code 0172 'system too lean'. What's puzzling me is I don't get either of these, just the 0170 'fuel trim malfunction'. I'll keep a close eye on fuel economy over the next couple of weeks and see if it's normal, and have apoke about up the exhaust, although the note sounds normal. thanks again.
Fault code 0170 - what's that all about then? - SpamCan61 {P}
Just for the sake of future generations searching the forum for fuel trim problems, I thought I'd update this. The problem turned out to be a dead lambda sensor, the first replacement was also dead which confused the issue somewhat :-((.
Fault code 0170 - what's that all about then? - cherry
Just out of interest, was your temperature gage working when your car went wrong?

Mine has been playing up for a couple of weeks with a similar fault, also bringing up the 0170 fault code.
My dad changed the mass air flow censor which is combined with the temperature censor, which seems to have got rid of the fault, but the temperature gage still isn't working, so I'm a little worried it could be useing too much fuel, although it doesn't appear to be.

Oddly enough, it also came up with the code 1555, which is something to do with Cruise Control, which, even more oddly, my 2001 Astra Cabriolet doesn't have.

Did anyone's do the same?
Fault code 0170 - what's that all about then? - Screwloose

Wow; are you wide of the mark. First; what engine does yours have? [Engine code would help too, if you know it.]

P1555 - MAF signal/throttle position signal - implausible relationship.

The engine coolant temp sensor is most definitely not in the MAF - that's the intake air temp sensor.

Did the P0170 come up before or after the MAF change - and where did that MAF come from?
Fault code 0170 - what's that all about then? - SpamCan61 {P}
My temperature gauge was working fine - appears chronically overcooled as normal :-/.

As Screwloose states the MAF on these*, unlike my lovely green X20XEV Vectra's, combines the airflow sensor with an inlet air temperature sensor.

* GM part number 90530463, a Siemens part, on my Z18XE engined Zaf.
Fault code 0170 - what's that all about then? - garyb
Hope the following helps out:

I have a 2001 1.8 Zafira Elegance 123BHP which I have owned from new and I have fully serviced every 6 months since new. The car is like showroom condition , inside. outside and under the bonnet but over the past few months I've had a couple of engine managment problems, but I like the car so much I do not wish to part with it. Only last year it towed my caravan to the South of France and back return 27mpg towing!

Anyway here are the engine management problems:

1) Driving along the motorway and the temp gauge suddenly drops , the yellow engine check dash light comes on and power drops and fuel consupmtion goes up. P0170 code reported, problem solved by replacing the coolant thermostat. The thermostat was broken. The replacement unit comes with new temp sensor and housing all preassembled approx £35. Piece of cake to fit it. Problem gone away. Temp gauge constant, engine light cleared and no longer on. The part has been redesigned a number of times according to Vauxhall. This is a real red herring if you believe it's linked with anything else. Don't waste your time and money, just replace it

2) Today, after a number of months with no light on, the same dash light came on again, this time with P0170, P1525 and P1550 codes reported.

I have not fixed this yet but I have noted the following:

I replaced the rear box a little while ago and I did notice the front pipe of the middle box had been vitually blown off the down pipe fro the cat with pure pressure. So I think the middle box might be partly blocked, so causing the P0170 lean exhaust if the system isn't quite running properly (see below). I will replace this as a matter of course (cheap enough)

The codes P1525 (Limp Home Position Error - mechanical fault) and P1550 (Elextronic Throttle Control - Engine Stop) I think are the real cause of the upset, ie the throttle body is gummed up with residue from the bypass gasses, and parts of the unit aren't working properly.

I will keep progress posted here. If anyone has any suggestions (not rude ones ;-) ), I'd love to hear them.
Fault code 0170 - what's that all about then? - Screwloose

P0170 Fuel trim - malfunction. [P0171 is too lean, bank 1.]

P1525 Electronic throttle system in limp-home position - malfunction.

P1550 Electronic throttle system in emergency mode.

You may need a new throttle body; the EGR gases don't pass through it. Proper checks needed first though.
Fault code 0170 - what's that all about then? - SpamCan61 {P}
>>the throttle body is gummed up with residue from the bypass gasses, and parts of the unit aren't working properly.

Yes, the throttle body on my Zaf. was well and truly gummed up, although a good clean out didn't help the problems I had above, it does idle much more evenly now though. Presumably this is blow-by gasses ( not sure that is the right phrase?) from the crankcase via the cam cover breather pipes getting into the throttle body; not from the EGR, as Screwloose points out.
Fault code 0170 - what's that all about then? - garyb
Thanks for the extra info on the codes (screwloose)

Definitely the blow by gases out the top of the engine. I do not have an EGR on my Zafira, just a blanking plate. They are only there to control the nitrogens during high output and are probably more hassle than they are worth. My Vauxhall 1998 Omega 2.5V6 does have an EGR, but when I removed that to check it in case it was affecting the idling, the EGR turned out to be perfectly good, it was the idle valve instead that needed cleaning. The EGR gas output is burnt product anyway and only amount to a powderlike coating.

As far as my 2001 Zafira 1.8 is concerned, on Saturday (26th Jan) I removed the throttle body well, covered the MAF for protection and completely cleaned the throttle body back to metal only. I also cleaned ALL associated pipe work that leads to the throttle body. The throttle body had about 1mm of black residue all over which easily washed away with carb cleaner. Before cleaning I noticed that the residue was indeed causing the throttle to become very sticky around the idle position when I moved it manually. It looked like the edge of the butterfly was definitely the culprit here, although the butterfly spindle had quite a bit of residue too. Quite significant amounts of residue (dry carbon like compound) was also found in the pipe work leading to the throttle body, but the 1mm crankcase pilot hole was for some reason perfectly clear. I also cleaned out the front of the induction manifold as far as possible. Nevertheless after having the error codes cleared down, and then a full week's worth of "hard" motorway driving" in an attempt to reproduce the faults, no error codes at all. Now I haven't even got round to replacing the middle exhaust box yet, but idling is much smoother and fuel eccomomy has improved by 2-3mpg for exactly the same road route. As much as I tried to abuse the engine with very fast driving back to idle, then back to high speed followed by instant overun (off the throttle), which is when the light came on before, I could not get that yellow light to come back on. My guess is that the error codes are purely a result of the ECU's inability to control the electronic throttle in normal mode nor in limp home mode when activated, hence P1525 and P1550.
I still intend to replace the middle box, as these systems seem to be so sensitive on the P1070 oxygen front. The middle box is 7 years old now, it only takes a slight break down of the internals.

(SpamCan61) are you sure you cleaned the long pipework leading to the throttle body properly, mine had slugs of dried carbon compound wedged in them. Also did you clean that butterfly spindle really well ?

I will keep posted here any futher problems that occur in tandem woth the P0170 code.
Fault code 0170 - what's that all about then? - wmathias


I know this is a bit old but just in case you're reading this, did you resolve the problem?

My symptoms are: Engine (ZE18) runs perfectly, but revs fall every 2 seconds and then return, for example, if the throttle is set to 4000rpms then engine will keep running but revs will drop to 2000 for 2 seconds and then return to 4000 again for 2 seconds and then back to 2000 again. All this happens without the butterfly valve moving (or the throttle pedal being pressed). My temperature gauge reads zero, even if i drove the car for a week non stop. Whether this is correct or not working I'm not sure.

I'm getting codes 0170,0100,1555,0110,0130 (o2 sensor), 1525(limp home), 1550(electronic throttle control reduced power), 0115(engine coolant temperature curcuit high temperature). Throttle body has been removed and cleaned thoroughly, (including very small hole).I did notice an improvement in throttle response after this The 0130,1525,1550 and 0115 only showed up after the throttle body was cleaned?

I've also changed the spark plugs, the old ones all looked ok and in the same condition as one other.

Help would be much appreciated


Edited by wmathias on 03/02/2011 at 12:00

Join the discussion


Buying Advice

Honest John's Newsletter

Connect with Honest John

Facebook YouTube