Injector warning light plus engine fan on cold weather 2 - Alfa Romeo Forum
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(Post Link) post #1 of 10 Old 15-02-08 Thread Starter
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Cry Like A Baby Injector warning light plus engine fan on cold weather 2

Ciao fellow 155isti,

I am so bummed... Symptoms are still there, reasons unidentified: driving by cold temperatures (32 - 40 farenheit), injection light comes on, engine fan kicks in, water temperature shows at minimum.

I'm mad because my first elettrauto identified the thermostat as the problem, and changed it. The problem re-appeared after 2 days and I'd realized the guy tried my car over the huge distance of 1.2 km, so I instantly gave up on him.

My mechanic ran a more detailed Bosch diagnostic and came to the same conclusion, except he was professional and showed me the actual error codes. The thermostat was returning "impossible" values and the AFM seemed to not send signal at times.

In went a new thermostat, but the problem showed up again, except the AFM issue didn't show up anymore.

So my mechanic took my car to an elettrauto he trusts, who re-wired the thermostat to the ECU. The car being 12 yo, it makes good sense that some wires are getting old.

Additionally, the ECU started showing errors coming from the Lambda, so in went a new Lambda. Fine, I got the car 70,000kms ago, I can totally believe both the AFM and the Lambda need replacement at this point.

But... This morning I drive my car to work by 32F, and after 7 miles, same thing happens again.

So I'm taking my car back tonight for another Bosch diagnostic, but I'm confused. What's left apart from the thermostat and the wire to the ECU that could go wrong? Faulty ECU contacts? Faulty ECU?

Help!!!
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Re: Injector warning light plus engine fan on cold weather 2

bad ground?
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Re: Injector warning light plus engine fan on cold weather 2

Fault coding is only good if the ECU is fine, your error codes sound spurious to me and that would make me slave in a known good ECU and try a diag then. Trouble is that not everyone has a spare ECU and as Cuore suggests it could just be a bad earth somewhere.
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Re: Injector warning light plus engine fan on cold weather 2

Sheesh, I hope not. I had the fuse panel changed last year for that very reason. Thanks for the hint though.
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Re: Injector warning light plus engine fan on cold weather 2

Well that said I do have a spare ECU still to be installed... from Squadra. That said you mount the ECU chip on a chip support, itself on a set of boards, and grounding could go wrong on that circuitry as well. I get the feeling I'm not there yet...
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Re: Injector warning light plus engine fan on cold weather 2

Quote:
Originally Posted by Smaky View Post
Fault coding is only good if the ECU is fine, your error codes sound spurious to me and that would make me slave in a known good ECU and try a diag then.
......
ECU is VERY unlikely to be the problem. It may be possible if you've had water leaks into the passenger footwell, or if someone has opened it up and tampered with it...... but apart from that no reason for it to fail.
Also you cannot just swap in a different ECU, you also need the code box and a transponder key from the donor car, and maybe also need the ignition barrel.

btw have you replaced the water temp sender? Sounds like this is the fault to me. It is located in the thermostat housing BUT does NOT come with the new stat when you buy it. Replacing the stat will only increase your water temp when cruising and make it reach operating temp quicker. THe ECU knows nothing about the stat.

The temp that the ECU is talking about is the signal coming from the water temp sender. If you've not got a new one then the old (faulty) one is now in your new stat..... hence the same problems recurring.

First thing to do is get a new sender....... obviously if you've already done that then pls ignore.....
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Re: Injector warning light plus engine fan on cold weather 2

Sorry, didn't mean the thermostat then, indeed the temperature sender. That was changed twice now.

I just heard from my mechanic that the problem appears to be on the ECU boards temselves: faulty soldering, due to aging. My "yo-yo" tachometer problem was of the very same nature.

I can only wonder what the root cause of both the tachometer and the ECU faulty soldering might be. I do not live right by the sea - as a matter of fact, there's practically no rust on the chassis - and the weather is quite sunny here, so humidity is not the issue.

Would that be because the roads are so filled with potholes here that vibrations would eventually "destroy" that type of soldering? I do remember my speedo being very sensitive to the fast rolling type of "bumps" you can find on highways. Or just a bad batch?

And hopefully my 155 won't die in an electric fire too soon. But I wonder: that's the 4th electrical problem so far in so many years. Not reassuring.
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Re: Injector warning light plus engine fan on cold weather 2

Have you changed the thermostat as well?

If you're seeing low temps on the dash gauge then it's very likely that your stat is stuck open. Low running temps do cause the injection light to come on in cold weather.
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Re: Injector warning light plus engine fan on cold weather 2

Thermostat is working fine, thanks for the advice mo4.

And the final verdict is: faulty ECU. Thermostat is good, temperature sender is good (new), wire is good (new), ECU after electrical checks appears good except for engine temp.

To solve the issue without hunting for a new ECU, my elettrauto made the engine fan independent from the ECU, i.e. it triggers based on engine temp independently. Problem solved, the ignition led does come on for a few seconds on very cold mornings (the now usual "implausible temperature sender value"), then goes away as the engine warms up.

Good enough, now I hope the rest of the ECU holds on for the next 2 to 3 years...

Thanks for everybody's help!
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Re: Injector warning light plus engine fan on cold weather 2

No problem, glad I nailed that one down for you.
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