C3 Phase I random starting issues

[frenchc3]

Hi Folks!

Thank you for this useful forum which has helped fix some small issues. Now I am forced to ask because I can't figure out the issue.

Shortly, I have a 2008 C3 1.4 l, automatic.

I have been experiencing intermittent and random starting problems. Either the starter doesn't start or it turn for 4-5 seconds when the engine seems to start turning but doesn't start. I have two warning messages: faulty start&stop and faulty anti-lock. I checked code and there was a U0401 code fault, I cleared it but didn't come back even during the starting failure.
Unfortunately I only have one normal key which is the copy of the original key.

Battery voltage at rest is 12.6v and while running is 14.7v, and goes down to ~10.6v at start, this looks ok.
I have checked the tension of the accessories/alternator/starter belt (they share the same belt) and the spring extension is ~ 85 mm so within range of the manual and the belt is tight at the touch.

It seems the only things that work are removing the key and waiting a few minutes, but sometimes I had to disconnect the battery.

I searched various forum but am not able to understand what the problem might be.

Many thanks in advance!

[mickthemaverick]

The battery voltages you give are not any good. When dormant you should get a minimum of 12.7V and during cranking it should not droip much below 11.5V. The 14.7V shows that your alternator looks OK but you may still have a dying battery!!

[moizeau]

Sorry Mick, I disagree, the batt voltages look good to me. I'd be checking the starter solenoid voltage, starter motor voltage and battery earths first off.

[PaulC5]

On an 18 year old car there is a good chance the starter motor is the problem, possibly its brushes are worn out.

[ozvtr]

I have been experiencing intermittent and random starting problems. Either the starter doesn't start or it turn for 4-5 seconds when the engine seems to start turning but doesn't start.

The start/stop system does not have a "starter" per se. The system uses a modified alternator as the starter and it has it's own ECU to run the system. While the principal is simple, the system is complicated.
Your problem most likely lies in either the alternator/starter, the control module or the auxiliary battery. The auxiliary battery is the cheapest thing, and if it's never been replaced you could try a new one. It has nothing to do with actually starting the car but it supports the electronics, and they don't like low voltages. Again, I don't know if that's your problem, but it's about the only thing that you can try.
Well, another thing you could do is take a look at the electrical connections of the alternator/starter and the control module (follow the big wires from the alternator/starter to the control module). I'm lead to believe the control module is in the engine bay. Look for corrosion of the joints and electrical contacts.
IMHO you need to take the car to a Citroen or Peugeot dealer and have it looked at.

[ozvtr]

I have two warning messages: faulty start&stop and faulty anti-lock. I checked code and there was a U0401 code fault, I cleared it but didn't come back even during the starting failure.

Intermittent comms codes are not unusual and I suspect it's connected to the ABS "fault". The "fault" is most likely the ABS module whinging that it's not getting data to or from the engine or the transmission. From time-to-time the data bus can get "clogged" and data doesn't go where it needs to go. But these faults tend to be very intermittent. And if the problem does not occur again after a certain period of time, they clear themselves.
Pay close attention if and when the "faulty anti-lock" message comes up (if it ever comes up at all). I would suspect that this is a separate fault to the start stop issue. HOWEVER!!!! The start stop has A LOT of parameters that MUST be satisfied before it will operate (like all the doors need to be closed, ETC)! So you really cant discount anything. BUT, if it doesn't pop up again, I wouldn't worry about that.

[frenchc3]

wow guys thanks a lot for the responses!

I had in fact read about the auxiliary battery which should be located under the seat, I will try to do that first. I have also cleaned and slightly sanded the battery terminals. The battery is about 5 years old, not super old, but we do a lot of shorter trips, but I just recharged it last week.

ozvtr is absolutely right about the alternator, it's a very weird setup and it creates more problems than anything. I had the belt and tensioner replaced, and it was really expensive. Incidentally, the start&stop failure message started appearing about 2 years ago after when the belt+tensioner were replaced. I don't know if it's a coincidence or something about the ECU that doesn't like non-original parts. The problem is more recurrent in the summer also. I looked at the auxilliary battery and it's a 12v, 4aH 4A, I measured 11.7v, I guess it's within specs.

Could it be that the starter part of the alternator is faulty but not the alternator? Because the battery voltage when the engine is running suggests that the alternator is doing its job, as mentioned by mick.
Would someone have a video, manual, or picture of how to check starter solenoid voltage and starter motor voltage? I see the earth wire connected to the battery negative pole, any idea where that ends up? On the gear box?

Thanks in advance.

[moizeau]

Sorry, I didn't realise this engine didn't have a normal starter motor so apart from checking the earth connection is clean the rest of my post is irrelevant

[mickthemaverick]

Sorry, I didn't realise this engine didn't have a normal starter motor so apart from checking the earth connection is clean the rest of my post is irrelevant

That explains your disagreement with me about the voltages Pete. The cranking voltage is much more critical on this system and hence my concern. Now knowing the age of the battery and its usage pattern I am even more inclined to suggest the battery is the issue!!

[frenchc3]

Sorry, I didn't realise this engine didn't have a normal starter motor so apart from checking the earth connection is clean the rest of my post is irrelevant

That explains your disagreement with me about the voltages Pete. The cranking voltage is much more critical on this system and hence my concern. Now knowing the age of the battery and its usage pattern I am even more inclined to suggest the battery is the issue!!

I appreciate the suggestion, would you have any clue what could be the relation with the "anti theft fault", "stat and stop fault", and that simply the starter will not attempt to start at all in certain cases. My impression is that a dying battery will simply keep degrading over time, but I am essentially getting the same intermittent problems over the last year and a half. Wouldn't the problems become more and more often?

The auxilliary battery at 11.7v is ok?

[ozvtr]

I looked at the auxilliary battery and it's a 12v, 4aH 4A, I measured 11.7v, I guess it's within specs.

If the battery is five years old I would look at replacing it. You can not judge the status of a battery by measuring the terminal voltage. You can now buy cheap battery testers that do the job properly.
On revision, the aux battery only powers the dash and the infotainment system. It won't have anything to do with your problem.

Could it be that the starter part of the alternator is faulty but not the alternator? Because the battery voltage when the engine is running suggests that the alternator is doing its job, as mentioned by mick.
Would someone have a video, manual, or picture of how to check starter solenoid voltage and starter motor voltage? I see the earth wire connected to the battery negative pole, any idea where that ends up? On the gear box?

Ah...the starter/alternator doesn't work the way that you think. There is NO form of "classic" starter involved here. To put it simply, the stop/start control module turns the alternator into the starter. As I said the principal is simple but the execution is very complicated!
This is a post that you might be interested in >click here<. It includes a full schematic of the whole stop/start system (ignore the first diagram, it's not correct). It wont be exactly the same as yours, but it's close enough.
The heart of the system is the stop/start ECU, labeled 1015. The alternator/starter is labeled 1021.

[ozvtr]

would you have any clue what could be the relation with the "anti theft fault",

Wait, what! When does the anti theft fault pop up??? The anti theft fault will stop the engine from "turning over" on start up!! "Anti theft" means that the engine ECU did not get the correct (or any) code from the key.
The plot thickens!
More information please.

[frenchc3]

would you have any clue what could be the relation with the "anti theft fault",

Wait, what! When does the anti theft fault pop up??? The anti theft fault will stop the engine from "turning over" on start up!! "Anti theft" means that the engine ECU did not get the correct (or any) code from the key.
The plot thickens!
More information please.

Sorry, I mentioned this briefly in the initial message but probably wasn't that clear. I also went through the other very long thread and the issues are similar. The only key I have is a simple key which is a copy of the original Citroen key (the two originals were lost or stolen). In the last few months I've been getting the message "anti theft fault" but not always, and the car will not ignite. It seems I cannot turn off the car and restart it immediately, but I have to remove the key and wait, as mentioned in the other thread as well. It's difficult to consistently reproduce the steps that make the fault messages appear.

As soon as the car starts, I always deactivate the S&S by pressing the ECO button, the "start & stop faulty" message appears either at startup or at the first time when the car tries to activate it.

[frenchc3]

On revision, the aux battery only powers the dash and the infotainment system. It won't have anything to do with your problem.

Thank you, I have reviewed that thread, it's not clear from the wiring, it's the 0004 I believe, and there are two icons, one looks like the infotainment system but the other looks like a chip. Are you sure that the small battery is not related to anything else?

I would like to measure the starter solenoid voltage and starter motor voltage. Do I need some specific adapter for my multimeter?

[ozvtr]

Thank you, I have reviewed that thread, it's not clear from the wiring, it's the 0004 I believe, and there are two icons, one looks like the infotainment system but the other looks like a chip. Are you sure that the small battery is not related to anything else?

The aux battery is actually labeled BB04, but it is hard to read. The devises that it supplies power to are; the instrument cluster (0004), the central display (72--), the radio (8410) and in this case the aircon control module (8025). It's all just to stop those from loosing power when the stop/start re-starts the engine.

I would like to measure the starter solenoid voltage and starter motor voltage. Do I need some specific adapter for my multimeter?

I'm afraid that you don't understand. It's not a classic starter motor. The alternator is literally run in reverse!
The control module (1015) supplies DC power to the rotor of the starter/alternator (1021) via the connector labeled 2V NR (two pin black). This should be around 12V. This DC current sets up a magnetic field in the rotor.
The control module then pulses the stator windings via the connector labeled 3V NR (three pin black). They are pulsed in series, 1-2,2-3,3-1,1-2,2-3,3-1 and so on. This "rotating" magnetic field "drags" the rotor around causing it to rotate.
The box labeled "CP" in the alternator/starter (1021) provides feedback to the control module as to what's happening in the alternator/starter, when it's running as a starter. This feedback is critical.

The only thing that you might see with a multimeter is if there is voltage at the 2 pin black connector and if there are pulses between the contacts of the 3 pin black connector.

To condense down that other thread, the problem was in the box labeled "CP" inside the alternator starter. The control module was not getting feedback, so it couldn't run the starter. It doesn't need that feedback when it's running as an alternator.

It's going to be difficult to fix because the occurrences are random.