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Old 26-08-10
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Engine management light flashing - CAT ??

Hi all, well just had a run down to Devon for work, on the way back after about 8 hours of faultless driving averaging 80 and 32 mpg , was just thinking how great the car had run, I know should never think that let alone say it !!, like mentioning how great the weather is just before it chucks it down !! ...

Anyway I pulled into services for a drink for about 10 mins, came out started off and rejoined M1 just after rejoining the engine management light decided to start flashing, if I slowed down to about 70ish the light would go off, if I sped back up it started flashing again, also engine seemed to be hesitatant/not sure if missing whilst light flashing is this some kind of mode set to protect the engine. Tried pulling off at next Jct and stop/restart engined but after a few minutes same again. Drove car yesterday on local roads 30-40mph for 30 mins or so and light never came on, looking in manual it says catalytic convertor problem.

Anyone had similar fault, did it just go away (fingers crossed) or get worse ? ... car is a CF3 so wondering whether to buy a diagnostic thingy to check codes or take it to garage ... what do I need to read codes PC etc ?? Cheers
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  #2 (Post Link)  
Old 26-08-10
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Buy yourself a cheap OBDII code reader. I got a stand-alone job for £20 from ebay. Not as sophisticated as the dongle and laptop types...but way more convenient to keep in the glovebox! If you can see yourself getting into the nitty-grity and worrying about all manner of fine details, buy a dongle type by all means!

Mine paid for itself in one fix. I had an intermittent fault with ABS/VDC/ASR/cruise. Reader told me it was the brake light switch, I fixed that with a pre-emptive switch clean, but mostly just adjustment I think, problem solved.

Fault codes can often be a bit generic, in that they won't always tell you exactly what's at fault, but they will give you a clue as to where to start looking.

OBD port is by the fusebox, under the panel to the right of the steering wheel. Black plastic cover - awkward to prize off at times.

Good luck.
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Old 26-08-10
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If its a CF3 any diagnostic tool should be able to give you a guid clue.

Pomeo
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Old 26-08-10
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Hi looking at Ebay would this work
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Old 26-08-10
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Yep - ideal. And just over half what I paid for mine...swine
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Old 26-08-10
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...but I just spotted the £9.99 postage...so I retract the 'swine'
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Old 26-08-10
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Apropos the whole code clue thing..on my 155, it had an intermittent warning light for ages. The stored code blamed the lambda. I replaced it (twice), tried many, many other things but eventually did find the problem with the lambda heater circuit which cured it once and for all. What I'm getting at is, sometimes (probably usually) the code you get is going to require some interpretation to find the actual fault....but don't be put off!
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Old 26-08-10
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Hi!
You may try to check the cable connection between e-gas potentiometer and throttle body.
The corresponding white connector is right in the gas pedal area. Unplug and flood it with contact spray.



Let me know, Chris
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Old 07-09-10
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thanks for the pointers ... however light went out for a bit so left it alone, but today has come on permenent not flashing car still drives Ok-ish slight hesitation sometimes ... ordered a code reader yesterday so hopefully may shed some light (however vague) on the problem.
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Old 07-09-10
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Maf? Lambda?

Water and oil ok? Just asking that for the sake of asking.

What's the car like as it goes threw the revs? Any flat spots?
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Old 07-09-10
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Water and oil both OK, had a MAF failure before and an other 166 and that seemed quite obvious with definite flat spots, this is not like that at all. Idle and tickover both fine, which seem to be a symptom of a Lambda looking at previous posts.
Only thing I notice is a slight hesitation (feels a bit like a cylinder missing) at fairly low revs 2-3K, but is very slight, and the light on of course ???
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Old 09-09-10
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Well got my U380 code reader today and plugged in, there were 5 fault codes
P0300 - Random/mulitple cylinder misfire
P0302 - Cylinder 2 misfire
P0303 - Cylinder 3 misfire
P0301 - Cylinder 1 misfire
P1135 - Not sure but found this on net Fiat ODBII DTC which says 3 things "In position 3 piston" - "Oxygen sensor B1-S2" - "Pre-heating resistance 1 above catal"

I am guessing the misfire codes are being caused by a result of whatever causes P1135, looking around found this post on another alfa site lambda problem bank 1. Which suggests a lambda sensor problem, but where to start to check ?? cheers
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Old 09-09-10
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I take it this is a CF3 motor (3 lambda probes, yes?), in which case, the codes do indeed suggest rear bank lambda...and if the final code is talking about lambda heater, that makes sense a well. Start looking at the rear bank lambda (obviously!), pay particluar attention to the cabling that feeds it, and see if you can measure the volts on the heater circuit as well, before you spend any money on parts you might not need.

All the symptoms and codes lean toward either a failure of the lambda heater itself, or the power feed to it - look for fuse, wiring and relay/relay socket issues. Don't immediately assume it's the lambda itself - it might be fine.

FWIW..and anyone who has seen my posts on this topic over the years will be sick of reading this...but I had a real pig of an intermitten fault on my 155 for a very long time. I finally caught it in the act of going wrong - it was a broken fuse feeding the lambda heater. Symptom was occasional injection trouble light under specific conditions (light load/low revs) and utterly random numbers on emissions tests from one minute to the next.

The symptoms you are seeing, along with the codes, look mighty familiar.....keep us posted
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Old 09-09-10
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cheers have read your previous posts re this, so shall start tracking down the wiring/fuse etc.
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Old 09-09-10
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Had exactly those error codes and an ECU light some months ago - replaced the rear bank pre-cat lambda, reset ECU and haven't had any problems since. CF3 has 4 lambdas, one before and one after the cats on each bank; and mechanic recommeneded that all 4 are changed at once... ouch!
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  #16 (Post Link)  
Old 09-09-10
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Cleared the errors, just been for a drive only a few miles, came back and checked codes shows 2 pending codes (what does pending mean rather than actual DTC codes), anyway shows P1135 again and this time P0130 - "O2 sensor circuit malfunction bank 1 sensor 1), so looks like lambda.

Which is which and where are they looking at my DTE it refers to left and right upper, they look like the pre-cat sensors, and I am guessing by the RR procedure my suspect sensor will be the right upper sensor (as it looks a swine to get out ) although I have seen on here that someone has replaced without lowering engine !

Looks like the electrical connector is in a junction box just under the resonator, I can open it OK and probably uplug sensor without removing all stuff above it, can I then just check voltage to heater to confirm fuse etc OK, would this also create a DTC that I can read just to confirm I am playing with the right sensor, if it is I can then just trace the cable to the sensor I guess. Also do I need a special tool to remove the sensor ??
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  #17 (Post Link)  
Old 09-09-10
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Bank 1 is rear bank, sensor 1 is the precat (the worst one to remove!). You can quickly confirm if you unplug its connection from the junction box under the airbox (grey one if I recall well) and see which error comes up.

I have changed it without lowering engine, just removed the heat shields and used an open ended spanner - doable if you have small hands, but you do risk skinning knuckles.

Do remember to reset the ECU afterwards so that the ECU learns the new lambda parameters - mine kept throwing up errors even after replacing the lambda until I did the ECU reset.
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Old 09-09-10
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If you can, when checking to see if the heater voltage is present, 'stab' into the lambda wires post the connector while it's still connected. That way you eliminate everything bar the sensor and you can be confident(ish!) that the feed is good (or not). What I'm getting at is, if you just unplug the sensor, you could conceivably read 12V for the heater using a DVM only to find it not present under load, due to a high impedance connection somewhere along the way. You could of course put a 21W bulb in place of the lambda heater to provide a sensible load for testing.

Unplugging the lambda and switching on would certainly generate a code or two....

The whole front/back left/right thing can be confusing...don't know if it harks back to the days when the V6 was first used or not, but I try to think in terms of cylinder numbers. 1,2,3 are one bank, 4,5,6 are the other, looking at the crankshaft damper/pulley end 1,2,3 are to your left. Of course, front/back came about once it got rotated 90 degrees and put into a FWD car.

Thinking about it, given the location of the probe, it has to be a bit less dependant on a working heater than the probes further down the pipe. This was the isue with my 155 - single probe, a long way from the engine, so it really needed the heater at anything other than moderate/full load and a fair few revs.

Could still go either way - probe or wiring....who's betting??

Getting closer......
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Old 09-09-10
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cheers lots of useful advice thanks
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Old 10-09-10
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Well, I may have given lots of advice, but time and facts will tell if any of it was useful or not!
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Old 11-09-10
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Well took a look today, measured voltage between the white wires with the sensor still plugged in, volts fluctuated between 8V and 11V not sure if that's what it's mean't to do or not as the sensor heats up. Between black and grey got about 0.7V

Verified I am working on right sensor by unplugging it and checking code, got P0135 bank 1 sensor 1, think I will be investing in a new lamdba
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Old 13-09-10
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Mm, that's odd.

8 to 11v sounds wrong. It should be a solid 12V or more (battery voltage) I reckon. Given a 4-wire probe has no way of monitoring temperature, I can't see how they could run it closed loop.

If heater volts are fluctuating (when they shouldn't) due to a wiring problem, that would give you problems. Only way to be certain it's not actually being driven with some sort of PWM drive would be to scope it. Or, can anyone say definitively if the heater drive is simply 12V, or if it's actively controlled by the ECU? A quick and dirty check might be to use your meter on an AC range. If it gives 12V or so, then it's likely a PWM drive. If it just bounces around a bit, then it's likely just noise from a bad connection.

0.7V signal is a valid number for a certain O2 value....whether it's right for the given point you measured it is another matter of course!
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Old 20-09-10
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Just about to order lambda anyone used Buypartsby seems cheap and a bit wary about not using geniune part such as AlfaWorksop
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  #24 (Post Link)  
Old 20-09-10
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I've used generic probes before with no problems. Others don't/won't. You'll get as many yays as nays I suspect.

TBH, I suspect it's more a case of the cheap/really cheap ones being nasty chinese out-of-spec copies rather than anything fundamentally wrong with the notion of not using OEM. Bit like the too-cheap-to-be-true MAFs.
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Old 29-09-10
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Quick one, car at garage now to replace lambda I took a look on drive and did not fancy it. Anyway anyone know how to remove the heatsheild or do you need to to remove the rear top lambda ??
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