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Doug, ASE Certified Technician
Category: Hyundai
Satisfied Customers: 8621
Experience:  ASE Certified Technician specializing in Asian vehicles
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I bought a 2015 Ford Focus as a builder. While I have been

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Hey Doug,I bought a 2015 Ford Focus as a builder. While I have been working on it, I kept the battery disconnected. I reconnected the battery and it won't start. It start, ran, and drove prior to this. Where should I start troubleshooting?

Hi Dom,

When you turn the key,m does it crank but not start, or does the engine not even crank?

Customer: replied 3 months ago.
No crank

Thanks. And the cables (positive particularly) weren't disassembled at all where one lead may have come off etc, just loosened and removed right?

Can we hook up some jumper cables or a charger to it just to make sure the battery hasn't run down while it was sitting?

Customer: replied 3 months ago.
Sure, I'll put a charger on it and get back to you.


Customer: replied 3 months ago.
One thing I noticed too was there was no sound of the fuel pump engaging. Do you think the alarm system disabled the ignition?

It really shouldn't if you didn't do anything related. Unhooking the battery in itself won't do anything to the security even if left a while.
I remember the older ones (like 12-13) had issues with the transmission controller causing a no-start condition, but I think by 15 that should have long since been resolved.
You didn't do anything that might be related while working on it did you (electrical work of any kind, unplugging things etc)? No risk of any fuses having blown? Do you have a different key to try just in case?

Only other thing I can think of would be to double check your connections... make sure your battery cables didn't corrode up a bit while being off or anything like that, double check the ground where it anchors to the chassis too, not just on the battery itself.

Customer: replied 3 months ago.
No electrical work was done. I just tried starting again and I could hear the fuel pump. The battery only has 12 volts so I am going to leave the charger on over night. No new fuse box. Will a low battery cause a no crank no start situation?
Yeah let's let it charge up. It sounds like the battery probably just depleted from sitting, that would certainly make it behave that way.
Customer: replied 3 months ago.
Tried it with the battery fully charged, still won't crank.

Thanks. If the cables are all tight and intact, none came loose while apart etc, ground is good, fuses intact and battery is assumed good at this point, the next stop is going to be getting a full code read done of all systems to see if the computer shows any faults. Again there isn't any real reason for it to do this from just having the battery unhooked; I actually have a 2014 Focus on my lot (that I can't give away) that's been here since early 2014... I've gone through three batteries including the original from just sitting unused and never had any issue with no crank afterward. Something must have happened either for the pats system to freak out (scan tool required at that point anyway) or something unrelated failed, if it wasn't anything you had worked on.

Customer: replied 3 months ago.
I pulled the starter relay and jumped it and the motor turned over just fine. I swapped the relay with another one and still nothing. I hooked up my obdII scanner and no codes. It ran just fine a few weeks ago.

Yeah you need a full scan tool not an OBD reader. That will only tell you if there is an engine management issue, and since you have no crank the engine management doesn't even come into it yet.

Customer: replied 3 months ago.
When I take it to the garage, what should I tell them I need to have done?

Just what you've done.... battery was disconnected for however long it was disconnected, whatever repairs you made, and battery was reconnected to a no start condition.
It's possible the pats system just freaked out from being unhooked a long time, but it isn't exactly common. In any event you would need the factory scan tool to correct it anyway.

Customer: replied 3 months ago.
I got it! First, I prayed. Then, I called the salvage yard and asked if they had ever had this problem. There is a big plug in the front that I disconnected when putting in the condenser and didn’t put back. That was it!

Always double check your work! I couldn't help but think there was something related there :)

Customer: replied 3 months ago.
You're right, I totally forgot about disconnecting that!

It's all good Dom. It's Friday :)

Customer: replied 3 months ago.
Hey Doug, I installed the new airbag sensors in the front. How do I reset the airbag light?

Hi Dom,
The air bag codes are stored in non-volatile memory so there isn't any quick way to reset them like unhooking the battery. You will need a scan tool with Ford SRS support through at least 2013 in order to go in there and clear the codes out if they did not clear automatically when the fault was resolved (very few SRS codes will do that).

Customer: replied 2 months ago.
Hey Doug. Does this look like it would do the same thing a dealer would?

Sort of. Those companies are resetting hard faults... collision reports, crash data etc. If that is what you have, then yes. If you only have a circuit fault, bad sensor, bad bag fault etc, then a scan tool makes more sense to do. If you have a collision report (not just a circuit fault from a bad sensor or deployed bag etc), then you would have to send it to one of those places... dealerships can not even remove hard collision faults. The reason for this is that by design those faults are unable to be erased even via scan tool in order to protect the occupant. The point being, if a collision was hard enough to deploy multiple bags and even at dual stage, the drivers that fire them are no longer trustworthy. They send a ton of current all at once and often damage themselves in the process to insure the bags deploy. So the hard fault is set so that the ecu would be replaced to insure good drivers and no problems if the bags need to deploy again.

Sending the ecu to one of those places they manually erase the otherwise non-eraseable memory so it can be used again, regardless of whether it is safe or not.

That said... if you only need a circuit fault erased etc (or don't know what the fault is), it is more logical to take it to the dealer or someone with an SRS compatible scan tool to erase it first. If you determine there is a hard fault from a significant collision and the ecu needs to be sent out for repair, then it is your call whether you would want to send it out for erasing or buy a new one.

Customer: replied 2 months ago.
I'll take it to a garage then. The airbags in this car were never deployed, but the sensors were destroyed. I was hoping the light would go out after I replaced the sensors.
That would make the most sense and see what you are really dealing with. If no bags deployed you'll probably just be clearing the sensor fault and being done.
Customer: replied 2 months ago.
Took it to the garage today. It gave the following codes: B0090, B0095. So what am I dealing with here? :)

B0090 is for a left front sensor fault, B0095 is for a right front sensor fault.

These are not hard faults... if the problem (be it broken sensor or wiring issue etc) is resolved, it should erase with a normal SRS compatible scan tool. It would not need to be sent out for those codes.

Customer: replied 2 months ago.
I installed new sensors I bought from eBay. Should I send those back and get them from Ford? Are they the same sensor for both sides?
I don't know if they are the same left to right on that model, but generally speaking yes they usually are.
If the ones you got are not new or not genuine Ford parts, yes you should replace them. This is not an area to try to save on... You risk the bags not deploying in an accident or (depending on how you look at it, better or worse) deploying the bags in error unexpectedly. You definitely want only new genuine sensors on there.
Obviously make sure you don't have any damage to the wiring that might have gotten overlooked too, but yeah if the sensors you got are used or aftermarket, I would swap to new genuine ones.
Customer: replied 2 months ago.
Is there a way to check if the sensors are good? They are genuine Ford sensors.
Not reliably. If they are genuine Ford and new, then I would consider there may still be damage to the wiring etc.
Customer: replied 2 months ago.
Hey Doug, one thing I forgot to mention yesterday is that there was an error message attached to the code that said, "wrong component installed." If I gave you the serial number on the part, could you verify if it's the right one?

The only data I have for front impact sensors on a 15 focus is CP9Z14B004A for both front sensors.

Customer: replied 2 months ago.
I think I have the wrong sensors, the part number on them is FR3T14B006AA. I am going to return these and get some from the dealer. I'll let you know what happens. Also, I found an app for the iPhone that reads airbag codes. Here is the link, It interfaces with the ELM327 WiFi dongle.
That's pretty different... If the part superceded it would usually be a similar number. Probably worth a call to Ford just to verify. If it isn't the right part it certainly will cause an issue.
I can't speak for that app, that would be nice if it works, just keep in mind the car is pretty new, if the app doesn't specify that year/model specifically, it could go either way.
Customer: replied 2 months ago.
I ordered the new airbag sensors. Once they come in and I install them, I'll let you know what happens. Have a great weekend!
Sounds good Dom, you too!
Customer: replied 2 months ago.
Put in the new airbag sensors in. Guess what? No more airbag light! :)

Fantastic Dom!

Doug and 4 other Hyundai Specialists are ready to help you
Customer: replied 2 months ago.
Well... I finally finished it. Here it is. Did everything by the book. Hope it sells fast!
Fantastic Dom!
That thing looks super sharp, and the mileage/price ratio can't be beat. I'm sure it'll be gone in no time.
Customer: replied 2 months ago.
Thanks Doug! One of my headlights on this car is flickering. Where is a good place to start looking for the culprit?
If it is just one, then it isn't too likely to be anything major like an alternator issue etc, as you would expect both to do it. I would start by tracing the wiring backward from the headlight... I would bet you are going to find one of the wires chaffed/weakened affecting ground or something like that.
Customer: replied 1 month ago.
Hey Doug. I noticed that my 2015 Ford Focus SE occasionally shutters when I accelerate from a stop. It only has 10,000. Is that something I should be worried about?

I would probably take it in to Ford and have them check it out... reason being we've seen a few of the recent Focuses having transmission issues similar to that which were covered under a recall. Best to make sure that isn't it first.

Customer: replied 1 month ago.
Sounds good. Will do. What did it end up being?

I believe it was a clutch pack kit they put in there.

Customer: replied 1 month ago.
Did that usually fix it? I made an appointment with the dealer for Wed. next week. I have been reading online that some people still had the same problem even after having the clutch pack kit replaced.

We have had three of them traded in with the shuddering on accel and all three were resolved with the recall.... however I believe the first one they actually replaced the entire transmission as it was before the service parts were available.

Customer: replied 1 month ago.
Okay, that makes me feel better. I made an appointment for Wed. this coming week. I have a p0456 code on the Mitsubishi. I smoked it through the gas tank and clamped off the line going to the charcoal filter. Didn't see any smoke, except for a little coming out the exhaust. Where should look next? Thanks!
Check the vent solenoid and purge solenoid are both sealing properly (hand vacuum pump, should be able to draw 30inHg and hold with no leakage... Purge at rest, vent while energized).
If nothing... And you are sure there are no smoke leaks, suspect the gas cap as that is the only part not being tested when you smoke it and they are pretty common to fail (not to mention aftermarket ones rarely seal).
Customer: replied 1 month ago.
Thanks Doug. Took the Focus to the dealer. They said the data on the transmission was not anywhere near close to what Ford would consider a problem. They told me to use more gas to accelerate after a stop to prevent any future shuddering. One a different note, the man I bought the car from switched out the rear bumper cover with another car and put on a rear bumper cover for Park Assist. I'm pretty sure this car does not have that option. However, are there wires that run to the back of the car that could be hooked up to the sensors? Do the sensors in the bumpers also alert the driver about proximity? Just curious.

I'm not sure if the wiring is factory equipped on those (Regardless of option installation) or not unfortunately... I only deal with them used :)

Customer: replied 1 month ago.
Thanks. Hope you're out of the path of that hurricane!
Thanks! We are looking like we will get spared. Wednesday morning they were talking about it making landfall pretty much on my door step, but since then it has tracked much further west so hopefully we'll be ~100mph max when it passes up from the looks of it.
Customer: replied 1 month ago.
Glad you guys were spared! My son bought the Focus for cost, so he got a really good deal. :) Anyway, the tail lights don't work. The signals and brake lights work. Where should I start looking to fix this? Thanks.

Start with your fuses/bulbs of course... if the tail lights didn't work at all (just didn't notice before), check in the rear area for any damage to wires, lamps being unplugged etc.

If the front markers are working, more than likely there is something unplugged or crimped etc, assuming no bulb/etc issues.