A 2007 Ford Escape XLT 2.3 4x4 keeps draining the battery. After a battery boost the customer was able to bring it in. I put a low battery charge on it overnight. The first thing you want to know when looking for electrical system problems is that you have a fully charged, good battery. All of your testing is based on that.
Once the battery was fully charged I did a quick test that I had alternator output. Just watch that the voltage at the battery increases once the engine is running.
Next up was to test the battery but I would need to disconnect it from the car before testing because if there was a system on the car causing the battery drain it could interfere with the battery testing. I didn't want the system to lose power or memory but I didn't want it connected to the battery. Fortunately there is a tool for just such a situation!
The memory saver provides alternative power to the system so that I could disconnect the battery for testing. Just connect it to the diagnostic link under the instrument panel. There was no problem with the battery.
The battery was charged and good. The alternator was working. I put the cables back to the battery and disconnected the memory saver. After the basics checked out fine it was time to measure actual current draw on the battery. You have to allow a reasonable amount of time for system modules to timeout and go to sleep. If you start testing current draw while a module is active you will be looking for a system problem that isn't a problem but a normal condition. The amount of time that is reasonable varies. You can try a test after an hour, or less if you are in a hurry but if the draw is high don't get excited about it at first. Just wait another hour and check again. If you still see too much draw after three hours you are safe to go ahead and trace it down. I use an amp clamp to get the measurements so that I don't have to break a connection and trigger another wait for a timeout. This vehicle had two leads off the negative post. Depending on circuitry, the excessive drain can be on either lead so measure each one at a time.
I did have higher current draw on one lead than the other but 58mA isn't excessive. Apparently this was an intermittent problem because up to that point I saw no reason for the battery to be going down.
I mentioned that I try not to disturb circuits when testing for draw because of the added time waiting for timeouts if a system wakes up. I'm not sure if you are aware how a door latches but there is a striker on the body.
When you close the door the latch in the door closes over that striker and holds it closed until you release it with the handle.
Now a few cars still use door jamb switches to know when the door is closed. The closed door pushes a button in and from the position of the switch the system can tell the door is closed.
Most cars though, and this Ford Escape in particular use a switch that is part of the door latch to determine if the door is closed. Typically on a job where I'm trying to trace excessive current draw I'll be disconnecting things, removing fuses, etcetera and I don't want the added aggravation of triggering draw based on my opening and closing the driver door so I close the latch with a screwdriver and leave the door open. As far as the system is concerned the door is closed and I'm free to enter or exit as needed. Is that somehow related to quantum physics? The door is open, yet it is closed. No clue. Anyway there is a reason for expaining the door situation.
Since the problem was intermittent and not making an appearance at the time of the draw test I needed to take a look at the stored memory of the vehicle for clues. That possibility is why I had used the memory saver to keep the stored information from disappearing. I turned the key on and connected a scan tool and entered the vehicle information, preparing to scan the systems. When you turn the key on but don't start the engine there are warning lights that come on for a few seconds as a bulb check, then go out. I noticed something that looked odd here though. The door ajar light stayed on. I thought maybe it was because the engine wasn't running but it stayed on with the engine too. I had noticed the dome light was turned OFF early on. If I moved the dome switch to DOOR position it was staying on. Occasionally the warning light and the dome light would go off as they should but it never stayed working more than a few seconds at a time. I spent a bit of time inspecting latches and opening and closing doors. I know of a Ford problem with the latch switches getting dirty and sticking but spraying lube/cleaner wasn't making any difference.
I decided I probably had a bad door latch switch but I wasn't sure that would be the dead battery problem because the dome light was turned off and most Fords will time the power off before it kills the battery in that situation. My mind was thinking this anyway, lol. I did have the scan tool hooked up and ready though so I took a look. I had three "battery voltage low" faults. One for the restraint control module, the instrument cluster and one for the general electronics module (GEM) which on this truck has an alias of SJB or smart junction block. I didn't think low battery voltage codes seemed clues since the problem was a dead battery. I would clear those later but I decided to take a look at the GEM data because the GEM is in charge of monitoring those door latches. Maybe I could see which door the truck thought was open. Well that was interesting! There may be a problem with that right rear door.
Ford has the PATS, passive anti-theft system that is supposed to deter a thief stealing your car. The PATS system uses programmed ignition keys and most people are aware of it. There is also though a perimeter anti-theft system to deter breaking into the car. There are nuances but basically the perimeter system arms when you lock the car. If a break-in occurs it will set off an alarm with horns and lights and log in the system as an "alarm event". I'm not sure what the limit is on how many alarm events will store but here I had eight events stored and each involved the right rear door. I doubt that the problem was a thief repeatedly opening the right rear door. I'd thought it more likely that the door ajar problem was in that door latch.
I still wanted to pull up the right rear door latch data item but I found only front doors available on either the Solus Edge or the OTC Encore. I found the pid available on the Autel MX808 however. This is why you need several scan tools in this business. No one scan tool is going to be helpful in every situation. It's kind of like thinking you'll only need one wrench.
I removed the right rear door panel to access the wiring connector at the latch. The black wire with white stripe is the ground. The pink with light blue stripe is a reference voltage from the GEM. It the door is open the switch is open and voltage on the pink wire. If the door is closed the switch is closed and the pink wire goes to ground. The other two wires are for the power door lock.
If the reference voltage from GEM to switch was good and if ground to switch was good I should be able to open the door and see battery voltage on a meter connected at the switch connector.
So the GEM, reference and ground circuit to the latch switch were good. I wanted to see what the latch switch was doing. It is supposed to close and ground out the reference voltage when the door is closed. That didn't quite happen. The switch was doing a poor job. BTW the GEM still saw the 4 volts as an open door.
Bad door ajar switch verified. This is part of the latch and power door lock assembly. If I grounded the reference voltage myself by twisting the two wires together the GEM should see a closed door. Of course that would mean when you opened the door the GEM would not notice but the door locks would still work and no more phantom right rear door alarm battery drains.
In this case we did the fix that best fit the customer's budget. Case closed, er.. door closed.
Thanks for reading!
Kenny@ggauto.repair
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