I would appreciate any advice for my engine warning light that has come on . Showing steady Yellow. Car is Nissan Micra Urbis 2006 1.2ltr 15k miles I notice that there seems to be something not quite right with the fueling , noticeable at around 2k-3k revs', but seems to run o.k when above this range. I am considering buying this piece of equipment, as It could be a good investment for future issues, no Idea where the U.S.B port is on the Micra though! Check Engine Warning Light I am reluctant take the car into a Garage, as I can for see this might cost an arm & leg, and if it's something I can do, such as change an Oxygen sensor I will still have the diagnostic tester for the future. Welcome any Ideas.
I would def invest in the equipment as it's universal and can be used on most makes of cars. Plus most garages charge £45 + to just plug in the diagnostics. Had exactly the same prob on my car and it did turn out to be an oxygen sensor.
It's a 16 pin plug called an EOBD plug after 2001 all cars will have them but your machine won't talk to all of them but it may do the most common if it does show an O2 sensor fault this don't meant it's defiantly the sensor all it's doing is the sensor is detecting the fault so don't be surprised if you Change the O2 sensor and the light comes back on
Well I bought the above mentioned tester, plugged it in , ran through the test sequence, everything appeared to operate as the instruction manual indicated, but the result was that no fault codes were detected. I still have the engine management light showing on the dashboard, and the cars engine is not performing 100%, symptoms of faulty fueling I would guess at. I have looked under the bonnet and had a wiggle at any likely looking relevant sensors, ran the test sequence again but still the same results. Any ideas anyone?
Are you a member of AA or RAC ? if so call them out, they have the diagnostic kit and can do what ever is needed including going to get the part thats needed and fitting it, sooooo much cheaper than a garage. Good luck with it
Si I have got the diagnostic kit, but it ain't picking up the fault! Good point about AA/RAC membership , I'm not a member though! Is the Lambda sensor the 'thingimyjig' poking out of the exhaust not far from the manifold?
Yup that's it! There could be another further along too.....but I doubt it, my impreza had two tho. One before the cat and one after.
John, this is often a lambda sensor fault which can be caused by bad fuel contaminating the sensor head with silicon residues or excessive carbon deposits. Lamda sensors get slow when they are old and tend to imperceptibly richen up the mixture a bit as they don't react as quickly as they should. Failed Lambda sensors were a big problem with Tesco fuel a few years ago when they wrecked 100s of sensors in the south east with a bad batch of fuel which was refined with too many additives. I have to say I ain't that keen on their fuel anyway. However it could also be down to a dirty hot wire in the MAF or MAP sensor which also tends to cause the mixture to run rich and upset the throttle response - which again can cause premature failure of the lamda sensor. Dirty MAF sensor wires can be the result of high mileage, not changing the air filter regularly enough or using an oil impregnated filter like a K&N which coats the fine wire in the sensor and makes it less responsive to heat loss. This then confuses the ecu and can make it run badly. The hot wire sensor element can be cleaned, but only with specialist cleaning chemicals (available on line) and has to be done very carefully as they are very fragile. Also you can get new ones online easily enough without spending ££s on one in a Nissan box. Some things you can try which are easy (to eliminate in the diagnosis) is firstly disconnect the battery for a few minutes to clear the ecu and allow it to reset to its as-built operating map. Doing this allows the ecu to then relearn the engine operating conditions over the next few hours of driving, in effect it has to relarn the feedback adjustments it has made as the engine and injection system has worn. It may allow the engine to clear built up carbon deposits on the sensor by running the exhaust gases at a higher (normal) operating temperature. You need to give it a blast on a fast road for a few miles to make sure it gets a full range of operating conditions. The second is to take the lamda sensor out and check it isn't covered in sooty deposits, if it is, it probably is not working properly. One thing I used to do was disconnect the lamda sensor when the engine was at its normal running temperature which makes the ecu substitute a normal running default value. If the rough running went away the lamda sensor was shot - however without it connected you will still get the light on the dash. You may end up having to go to Nissan for this but before you do it have a look to see if there are any engine management specialist in your area - they are usually much better at diagnosis than dealers and a lot cheaper for the repair.
Denzil Many thanks for your detailed advice, just what I was looking for. I was cautiously optimistic when I bought the tester, but I was thinking that if I could identify the fault; as the car has only done 15k and has a f.s.h, whatever the problem was it wasn't going to be that serious, and I would still have the tester which could prove useful in the future. I was surprised that the tester didn't pick up any fault codes although it appeared to work as it should. I shall disconnect the battery for a few minutes to clear the ecu and allow it to reset to its as-built operating map, and see what happens then. The Lambda sensor is easily accessible so I shall remove for inspection and give it a clean if it needs it. I do live in the S.E and generally buy my petrol from Tesco! I did make inquiries to engine management specialists I found by Googling, but they were too far away from me and not able to come to me. Their costs seemed very reasonable though £30-£40. I am reluctant to take the car into a Nissan dealer for cost reasons, If I can sort out the problem myself I will be far happier. I will let you know how I get on.
Denzil I intended to disconnect the battery today as you advised, but I realized that I don't have the radio code which I know I will need if the battery is disconnected. So I looked at the Lambda sensor and couldn't get the appropriate spanner on the body of the sensor as I was laying on the floor, it really needs a socket to undo it,but as there are 3 wires coming from the top of the sensor this prevented me from doing this. I decided to just electrically disconnect the sensor to see how the engine ran, and with the sensor disconnected the engine seems to run perfectly, so I presume I can accurately deduce that the sensor is the cause of my problems. With the sensor still disconnected I ran the diagnostic test again , this time one DTC was reported as P0031 which, according to the definitions in the book supplied with the tester is: H02S Bank 1 sensor 1 Heater circuit low. I don't understand the above , does that sound right? I am curious why no DTC's were reported on my initial scan ,as the engine management light on the dashboard was illuminated, the tester appears to work correctly as it picked up the aforementioned DTC when the Lambda sensor was disconnected. I'm having a think as to how I can jury rig a temporary 12v supply to the cars radio to enable me to disconnect the car's battery to clear the e.c.u. I would appreciate your thoughts if any.
John, the fault code you list is what you would expect if you disconnected the Lamda sensor on the engine side of the cat, this is the ecu recording that there is an open circuit on the heater supply lead to that Lamda sensor. On your car there is likely to be a second lamda sensor on the outlet pipe from the cat BTW. Also you should have got a second code related to the loss of the o2 signal from the sensor if your tester can log more than one code. I think the ecu should have recorded a fault if the engine light came up so you may need to clear the fault then recheck - however it is possible your ecu requires a computer connection to clear it rather than simply disconnecting the battery. It is also possible that the sensor is working adequately enough to not establish a firm fault indication in the ecu memory or that is has multiple related errors which your reader cannot deal with. I mentioned earlier about my distrust for Tesco fuel, well I have had repeated problems over many years with bad running on a Lancia, an Alfa and most recently my last car (an Impreza which needed at least 97 RON to run properly) would lose 10% mpg on a tank full of Tesco 99. It was undriveable on the two occsions I was forced to use Tesco 95 (both times when higher octane fuel was not available) so I don't use it anymore. Never had the same problems with other fuel suppliers (Sainsbury's or a branded fuel like Esso or BP). Don't make any diagnosis of the performance of alternative fuels until you have done a few (10s at least) miles on another decent quality fuel, the ecu needs a few miles to adjust the settings for the new fuel. Sometimes you get repeated fault codes which come back within miles of a reset which won't go away even when you replace the indicated suspect components and I have always suspected various suppliers fuel aditives as the cause. Remember the engine light can come up for a number of reasons some of which can indicate a potentially expensive fault so be prepared for a dealer check as it may be your last resort. Regarding the lamda sensors. OEM ones are usually £100-150 quid to buy but pattern or exactly equivalent independant supplier ones can be bought for as little as £30. Also you may want to have a look at the ecu manufacturer as it is likely that they are using a Eurpoean manufacturer for that system. I seem to remember Nissan UK using french supplied electrical systems (similar to Renault) which are known to not have the reliability of Japanese systems. Anyway good luck on this
John, if you're still having trouble come and see me, I'm not far from you and run a garage I have the diagnostic gear to check your car and won't charge you for it either :smile:
Denzil Today I attempted to remove the Lambda sensor for inspection, I was thwarted by the apparent impossibility of removing the exhaust header heat shield without removing all the radiator e.t.c. I have tried to get a spanner on the sensor's body; which has two parallel flats milled into the body, not a simple hexagon! so its very tricky to get sufficient movement of the spanner to undo the body. I assume there is probably a specialist tool that would make this task easier. If I had the car in the air on a lift it would probably be possible. I did some research today on the H02S Bank 1 sensor 1 Heater circuit low. and found out as you say, this code relates to the supply to the heating element being removed. I have found many Lambda sensors available from e bay, some in the region of 1/2 the price or less of the o.e.m sensors, so will consider getting one of those if necessary. I found out also that the car is fitted with 2 Lambda sensors, one each side of the cat', although I haven't managed to locate it yet by grovelling under the car. The disconnection of the sensor apparently resolves the problem with 'surging' and hesitation; presumably because, as you mention, the e.c.u has now resorted to a default setting, I am optimistic that the fitting of a new sensor will cure the problem. What I am unsure about though is how I will turn off the engine management light , and also why my tester, which is capable of recording multiple faults, didn't pick up any DTC's when the dashboard engine management light was illuminated. I suppose there is the possibility as you mention that the sensor is working adequately enough to not establish a firm fault indication in the ecu memory or that is has multiple related errors which my reader cannot deal with. Thank you so much for your concise, detailed, understandable replies, It's very much appreciated. Although I curse at the time, I actually enjoy the challenge of the fault finding process and learning new things, bearing in mind my first car was a Ford Popular 1200 side valve who's only sensors were the temperature gauge, I am amazed at the complexity of the modern car's sophisticated engine management systems. I have over the years done a lot of maintenance on my cars, but have never had cause to have anything to do with engine management systems, it's very interesting!
Juz Thank you for your very kind offer, I would very much like your diagnosis of my problem before I go spending out on the wrong parts , and would like to take you up on your offer. Where a bouts are you?
