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2005 Mazda 6 no start

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15 Mar 2020 12:57 #38381 by bwyl
2005 Mazda 6 no start was created by bwyl
2005 Mazda 6, 2.3 liter, car starts then stalls right away, engine is flooded and spark plugs are wet. No fault codes, fuel pressure is 60 psi(in spec), spark looks weak with dull orange at all plugs. Cleaned all grounds in engine bay, Vref at MAF is 5.0. Still thinking might be a bad PCM ground but very difficult to back probe this pcm. When the car stalls it seems like an electrical problem because as the engine cuts out immobilizer and CEL both turn on & off as engine cuts out. Once severely flooded won't restart. Battery voltage at coil and two other connections from coil go to PCM.
Any help would be awesome!

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15 Mar 2020 17:51 #38390 by Monde
Replied by Monde on topic 2005 Mazda 6 no start
With a bad pcm ground, you would most likely have battery voltage on the reference line because there will be no voltage drop at the resistor due to the circuit not being grounded. I could be wrong though.

Never assume, diagnose!

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16 Mar 2020 09:35 #38400 by bwyl
Replied by bwyl on topic 2005 Mazda 6 no start
At coil terminal B it should read battery voltage.


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16 Mar 2020 10:08 #38401 by jreardon
Replied by jreardon on topic 2005 Mazda 6 no start

bwyl wrote: At coil terminal B it should read battery voltage.


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Monde means you would see 12V on the reference wire (instead of 5V) at the MAF. Start stall hmmmm.... how dirty are the throttle plates, try giving that a clean.

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16 Mar 2020 10:10 - 16 Mar 2020 10:18 #38402 by jreardon
Replied by jreardon on topic 2005 Mazda 6 no start

bwyl wrote: At coil terminal B it should read battery voltage.


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Yup. Does it stay battery voltage while it's sparking?
Last edit: 16 Mar 2020 10:18 by jreardon.
The following user(s) said Thank You: bwyl

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16 Mar 2020 13:44 - 16 Mar 2020 13:46 #38405 by bwyl
Replied by bwyl on topic 2005 Mazda 6 no start
Nice wiring diagram mine from Alldatadiy is not great. I will check coil voltage while cranking, let you know thanks.


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Last edit: 16 Mar 2020 13:46 by bwyl.

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16 Mar 2020 20:35 - 16 Mar 2020 20:36 #38406 by bwyl
Replied by bwyl on topic 2005 Mazda 6 no start
Throttle body had been done earlier, but anyways changed the ignition coil. Spark at plugs is now blue and we have ignition. Engine is now running! Wiggled a zillion wires and relays etc to make sure I hadn't inadvertently repaired it another way. Road tested OK other than the fact now some TCM codes and in limp mode 3rd gear! I'll start a new post if I cant repair this. Thanks.
Last edit: 16 Mar 2020 20:36 by bwyl.

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