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  1. #1

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    16 Jul 2017
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    Saab(s)
    9-5 2006 1.9 TiD
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    ['06 1.9 TiD] Intermittent - engine not starting + TCS light on

    Hello all,

    Sorry for not doing the proper introduction (that will come later) but something really bad started happening to my car... and of course I'm in the middle of my vacation in a not so big town and no Saab specialized mechanics

    The issue - when trying to start the engine, the starter will crank but the engine will not start. During this "no start" issue I see also the TCS light lit on the dash and after few attempts of starting the temperature gauge goes down. Trying to read the error codes with an ELM327 code reader gives no result - by this I mean that the ELM cannot connect with the ECU.

    Frequency of this issue appearing - often but intermittently. It doesn't matter if the engine is cold or hot or how long it sat or if it was a rainy or sunny day.

    Eventually the engine will start and I know it will because the TCS light goes off as usual after turning the key. ECU registers no Pxxxx error codes (yes, now the ELM dongle can connect to the ECU).
    When engine starts it works as it should and the car drives normal (3 hrs drive)... until I turn it off. Sometimes it will start again as usual, but the next attempt ends with the TCS light lit and no start.

    Right now the car is sitting at the local Fiat service and they are simply scared to dig into it. The only thing they did so far was reading the codes with Bosh KTS540. It picked up two codes -
    U2105 (can bus, no connection to ECU) and the other about some multifunction relay operation disruption, but they can't say if they are old errors or because of this issue.

    I'll be there tomorrow and we will be checking the ground connections between the chassis and the battery but maybe you could suggest some other things to check?

    Car battery is an 1 year old and in good shape.

    The only thing I can remember is that this happened the first time when I was moving the car to a different parking spot and I drove over a big hole with the front left wheel. I did not hit anything, just felt the car rocked.

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  2. #2
    Saab Enthusiast Digger's Avatar
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    28 Oct 2016
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    Minneapolis Minnesota
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    241
    Saab(s)
    2006 9-3 Wagon
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    Ground connections could be your problem and always a good thing to check. Don't want to frighten, but also not going to ignore the elephant in the room and your ECM could be going bad. From your description of when this started, more than likely a relay loose in its socket got shaken hard enough to become a problem.

    Under hood electrical and the small block in front of the battery, check your relays for good tight connect on all spade pin female connectors. Easy to do on four pin relays, pull about half way out and wiggle up, down, left and right, if you have a loose connector you will be able to feel the difference. The center connect of a five pin is the one you need to check separate using something as thick as a male spade connector.

    If you get a no start when you go to test, check for sticking relays first. Taping the top of one relay at a time with the handle end of a medium size screwdriver and checking for operation after each tap is a quick way to find a sticking relay.

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  3. #3

    Join Date
    16 Jul 2017
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    Poland
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    Saab(s)
    9-5 2006 1.9 TiD
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    ['06 1.9 TiD] Intermittent - engine not starting + TCS light on

    So I have the car back, they checked the ECU cables briefly, checked the relays (all good) and cleaned the ground connections.
    Of course when I was trying to start it, the no start issue and the TCS light came back (in the morning they were able to start him quite few times).
    So, as usual, I got a little bit pissed and did one thing - move the cabling bundle going to the ECU, but this time using a bit more force and voila! Car started
    So yeah, it's surely the cabling issue, but I can take the car back home where I have a good electrician.

    One thing to add (I've noticed that just now) - I don't hear the fuel pump when the no start issue is active. I have swapped the pump relay (under the dash) but it looks like something else is making the relay not engaging. Is that the ECU task, or some other device?

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    Last edited by wengex; 1 Week Ago at 19:36.

  4. #4
    Saab Enthusiast Digger's Avatar
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    Saab(s)
    2006 9-3 Wagon
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    Even braded wires suffer from metal fatigue and brake at their flex point. On an engine it's usually within a few inches of the bundle clamp. A good clean break is easy to find with an ohm meter, it's those mostly broken's that can be a real pain. Braded wires have multiple strands and if 11 of 12 strands are broken the one remaining strand will show good continuity with an ohm meter and not be able to carry enough current to do the job. And yes your fuel pump could be caused by the ECU not getting what it needs, you could also have more than one bad wire in the bundle.

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  5. #5

    Join Date
    16 Jul 2017
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    Saab(s)
    9-5 2006 1.9 TiD
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    So I took the matters in my own hand, equipped with an multimeter, contact spray cleaner and a piece of a sandpaper.
    Battery went out and I've started checking all plugs and connections. Of course the ground connections were not cleaned, everything was dirty and corroded as hell! All grounds near the battery, all those big fuses (60A and 40A) and few pins in almost each of the harness plugs/connections had to be treated with the sandpaper...
    The only thing I wasn't able to clean is the other ground, the cable goes deep and looks to be screwed to the transmission. But I hope the ECU and other accessories (TCS/ABS) are not using it.

    I've also looked under the relay/fuse pack in the engine bay and all cables there look solid.

    So now I'm waiting for the cleaner to evaporate, the put everything together and we'll see if that helped.

    Wysłane z mojego SM-G950F przy użyciu Tapatalka

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  6. #6
    Saab Enthusiast Digger's Avatar
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    28 Oct 2016
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    2006 9-3 Wagon
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    Sounds like Fiat service didn't do a very good job of checking and cleaning your ground connections. The big ground connect can drive things nuts when cranking the starter motor, good idea to clean when you can, but if it wasn't the cable you tugged on to get the car started, it's probably not the cause of the problem your working on.

    What you're doing should get you running trouble free for years to come, wire brush on the screw threads of chassis ground studs doesn't always get the job done. Sometime corrosion is more than surface deep and if you find that, adding a ground strap to that point and a good chassis ground point needs to be done.

    When I get to where I'm looking at cable plugs and the bottom side of a fuse panel, I like to give every wire a little bit of a pull. Every now and then a wire that looks like it has a good solid connection slides out of the crimp connection and when it does it's usually the cause of many problems.

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  7. #7

    Join Date
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    Saab(s)
    9-5 2006 1.9 TiD
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    Yeah, all cleaned, still no joy... I even pulled the ECU but nothing wrong there and the harness going out of it does not show any physical signs of damage.
    It did started once and I've noticed that then (besides the fuel pump) I can also hear another electrical noise in the engine bay and it goes off few seconds after engine shut down. That noise is not appearing when the no start issue is on.

    Wondering if the problem lays with a different module (or the CAN itself?) because once I start the car, everything is working. So it seems that the issue/failure is only showing up initially, before trying to start the car. Does anyone knows if and what diagnostic steps are being taken before ECU decides to allow the engine to start? I do see the "check OK" message each time.

    Wysłane z mojego SM-G950F przy użyciu Tapatalka

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