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Discussion Starter #1
Hello everyone,

My Focus 2002 battery light had been coming on randomly over the last few weeks. Today it stayed on.

I ran the odo test mode (with dtc: none), but I am unsure how to determine from this information what my issue might be. I looked at a list of odo test sequences. New battery, solid terminal connections.


I would like to avoid taking it to the shop. I trust my local shop but I can hardly afford an expensive or unnecessary repair.
Thank you,
William
 

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One of those test mode functions is the voltage in the system.

First thing needed is a measure of that both stopped & idling by the test mode or a separate voltmeter. Add A/C volts to the running test.

DTC's from test mode are only for the inst. cluster so they aren't often much help.
 

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Discussion Starter #3
Yes, I understand. What I am trying to figure out is if there is a way to diagnose the battery light issue from home using the odo test mode and an ohm meter.
Thank you,
William
 

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2004 Focus Wagon, Zetec DOHC, Auto
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Scroll through the test functions and find the one that says "b 12.2" (exact reading will be dependent on your voltage). It is about 14-16 steps into the sequence...I don't remember for sure.

Now that your light is staying on, that should make it easier to find the problem....better than having a light that comes on and off.

You can also run by a parts store and have them do a battery and alternator test for free.
 

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The odo "b" test is at 12.4 at key on no start, and rises to 14.xx after engine start. Can we rule anything out based on this?

I will take it by the parts store later today.
 

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If your voltage is rising back up to 14.xx with car running and loads such as lights on, then that usually means the alt is good.......but not always as I had a bad alt that charged and still threw a light.
 

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There's also a sensor fuse (#11?) that will light the light if not making good connection or bad.

Look up the right one in your manual & pull it for a good look/test.

Shame to go through a bunch of possibilities & miss a simple one.

(it's happened)
 

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Scan for codes via the OBDII port - not the instrument cluster (odo) test as pointed out - and you may find a pending P1246 code (Generator Load Input Failed). It may not trigger the Check Engine Light until it fails completely.
Also it's helpful to leave the car in odo test mode and monitor the voltage as you drive. If it's an intermittent problem, you'll see your 14.5 V drop randomly (and quickly) and my experience is it tends to do that after warming up fully.
You may want to also consider trickle charging your battery to keep it topped up until you locate the problem source. Don't strand yourself while testing.
 

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There are 2 ground wires coming off of an 02's battery: a bigger one, and a tiny one. The tiny one breaks loose or gets very worn right at the connection to the car. PS: if that tiny ground wire breaks totally, your car wont even run!

Also, the first gens have the infamous positive wire melting problem. Pull the plastic loom off of your 2 positive wires. One goes to the starter, one goes to the fuse box. Check the whole run of each for a melted spot sitting against metal.

Coil pack can cause a batt light, but you would be experiencing bad surges/ power cut-outs if that was it.

I recently put a cheap autozone acc belt (they didn't have Gates) on my zx that must have been an inch too loose. Sqealed like a pig on start-up and under heavy bass music load on the alt. It would constantly give me a batt light cause the belt wasn't turning it well enough. I went and bought a gates after a few days of it, and all back to normal. In your case it could be the tensioner or idler pulley failing and slowing the belt. Do you hear any metal scraping sound from the pulleys when running?

Oh! 1 more!: Another time I got a batt light I found that my positive wire at the connection to the alt was broke and screwed up. Coulda burnt my car down it was so bad, so def check that just to have additional piece of mind. And while you're there, check the harness connection to the alt (harness with 3? little wires) for a broken wire at the harness.

If all else fails, run the car while you pull one fuse at a time til the light suddenly goes away. That will reveal a short. I would start with removing the cig lighter fuse. Those sockets for the lighter short out easy.

Sorry for the long read. Trying to throw a few ideas your way. Hope it's an easy, cheap fix for ya!

I was in your boat the other day sorta. Bought a zx3, and as soon as the delivery driver drove away, the dang car wouldn't crank. Had plenty of juice but wouldn't try to crank. After a few minutes I remembered the clutch safety switch problem they get. I stuck a paper clip in the clutch harness, boom.... starts like a champ now. Free fix... ?
 
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