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Ask Peter Zavarelli Your Own Question
Peter Zavarelli
Peter Zavarelli, Auto Mechanic
Category: Volvo
Satisfied Customers: 32153
Experience:  Technical Consultant at Just Answer
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A few months ago the battery on our 2007 manual Volvo XC90

Customer Question

A few months ago the battery on our 2007 manual Volvo XC90 went flat. The next day after charging it the engine suddenly died, something it has done periodically and randomly ever since. When the car is connected to a diagnostic machine it reports that there are injector faults. Over a six month period the car sometimes runs perfectly for weeks at a time with no problems, but then the ECU will shut the car down when driving. Once we have pulled over, the car will start perfectly normally after 2 minutes to allow the ECU to reset. The coincidence of all this starting immediately after the battery went flat makes me think that this is an ECU problem rather than an injector problem. Could re-mapping the ECU cure it?
Submitted: 5 months ago.
Category: Volvo
Customer: replied 5 months ago.
Another bit of detail - after a period of 4 weeks or so with no engine running problems, we managed to flatten the battery again (my son using a tyre inflator), immediately the cutting out problems started again.
Expert:  Peter Zavarelli replied 5 months ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

This can be a fault internally in the ECU itself and it is also possible the programming was damaged or wiped out by the ecu.I would have the fault codes read out of the ecu with a compatible scan tool or computer plugged into your model to see what codes are set.Any codes set then need to be diagnosed to then locate and repair this issue here.If no codes are set then I would see if a shop or dealer can try to reprogram the ECU to see if this resolves the fault and if it does not then the ECU may need to be replaced.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service, your 5-star rating is appreciated ( should be a link to click on here or above).You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 5 months ago.
Previously the fault codes have indicated a fault with the injectors but I an suspicious about this because of the timing - why should the injectors develop a fault at the same time the battery goes flat?
Expert:  Peter Zavarelli replied 5 months ago.

That shouldn't be an issue with the injectors themselves at fault if they were not an issue before the battery went flat.But if the engine ECU has lost its programming or programming is corrupted when the battery went flat it can cause this issue as well as injector codes.In some cases, all that is needed is to have the engine computer re programmed by a dealer to resolve this fault.But in other cases, it may need to be replaced.

Let me know if you need anything else and feel free to rate my help here or above ( should be a link to click on ) as this is how I receive credit for my time, this can be done at any time and you can still come back here and reply if needed.Your 5-star rating is appreciated

Thanks Pete