09 ford ranger, 4 cylinder, stick with 70657 miles. Started doing some wacky electrical things three days ago. Check engine light came on then gauges started fluctuating up and down. Yesterday, truck would not crank or start, theft light started blinking rapidly. Tried again after 2 hrs, truck started like normal and no idiot lights lit up, check engine light did not come on. Today, started right up, after driving 3 miles check engine light came on, then gauges quit working, idiot lights started flashing intermittently, odometer quit working. Couple more miles, check engine light went out, idiot lights quit flashing and gauges started working. Couple more miles and check engine light came back on and gauges quit working again, idiot lights started flashing. Repeated this cycle about 8 times decided to take truck back to house out of fear of being stranded. I know very little about auto electrical. Can someone please tell me what they think is going on and where to start looking for the problem? Thanks in advance, Ron.

 

Check battery voltage, key off
12.3 to 12.8volts is acceptable

Start engine, test battery again, 14.3-14.8volts is acceptable(alternator is working)
Let engine idle for 5 minutes and leave it running, re-test battery, should now be 13.5 to 13.9volts(voltage regulator is working)

Batteries tend to last 5 to 7 years, 2009 vehicle is 12 years old so could be end-of-life for its 2nd battery

2004-2011 Rangers have a full digital instrument cluster these are very sensitive to voltage fluctuations
2009 may have HEC test mode
Google: HEC test mode
And see if you can detect any issues, may also see some "B" codes that can ID a problem

 

thanks for the quick reply. Did as you instructed. With engine off, battery reads 13. After engine start, voltage reads 14. After 5-6 minute idle battery voltage at cables still reads 14. During the 5-6 min wait time the gauges quit working, check engine light came on and a couple of the idiot lights flashed intermittently. After 5-6 min wait was over I turned on headlights, AC and radio to see if voltage at cables dropped. Voltage at battery cables still read 14 however with those items turned on when I got back in truck the check engine light was off and gauges working. Does any of this help diagnose what’s going on? Will try and do HEC check next. Thanks for the help!

 

I was able to do the HEC test. As I started the test the check engine light started blinking. After gauge test I started the truck and after about four more button pushes, P7L54H code showed on odometer and it started a succession of about 5 beeps, a pause then 5 beeps. It kept doing this as I continued to push the button to the next readings. The beeping stopped when I turned the truck off. Does this help diagnose my truck’s electrical problem?

 

No, none of that helps but the battery and alternator are not the problem

It will have to go to Ford so they can check it out, be prepared to lose the truck for at least 2 days but more likely a week
Problem appears to be cluster issue, but can be engine computer as well, and when its one of those ONLY Ford can replace either and then re-marry them

The cluster and computer are "married" at the factory so one will not work without the other, to change either you need a subscription to Ford's "security" data center and that allows the subscriber to "re-marry" the new part to the old one, its done via internet connection with a laptop

But...............I have read that a shop specializing in Fords can have software that can do that, which would be cheaper than Ford Dealer