2000 Ford Mustang trouble codes engine light flashes

HERE'S MY POSSIBILITY

MAYBE YOUR PROBLEM IS MUCH LIKE MY NIECE'S WAS

WELL, MY NIECE DRUG HER '03 6 CYL. MUSTANG IN HERE THE OTHER EVENING (WELL NOW, A FEW MONTHS AGO)--BEEN SKIPPING AND MOSTLY SHAKING FOR A WHILE.

-THERE WAS NO CHECK ENGINE LIGHT OR CODES

MY FAMILY FEMALE PHILOSOPHY: DRIVE IT TILL IT WON'T GO NO MORE!

THEY SORTA FIGURED IT WAS THE PLUGS, BUT UPON POPPING THE HOOD WHILE IT WAS RUNNING, IT SORTA APPEARED TO BE HAVING A "LIGHT SHOW" GOING ON UNDER THERE.

WE REPLACED THE PLUGS (THEY HAD 'EM ON HAND), AS IT HAD BEEN TIME TO DO SO LONG AGO. THIS WAS NOT THE PROBLEM THOUGH

BUT THE LIGHT SHOW WAS THREE DIFFERENT PLUG WIRES HAD RUBBED "UNDERHOOD STUFF" UNTIL THEY WERE ARCING ON THE METAL COMPONENTS THEY TOUCHED

THIS IS ALMOST IMPOSSIBLE TO SEE DURING THE DAY, NOT REALLY BRIGHT AT NIGHT

THE ALL TIME AWARD WINNER WAS THE ONE THAT WAS RUBBING ON THE BRAKE BOOSTER---IT WAS GNAWED A THIRD OF THE WAY THRU!

THE WIRES "WORM" THEIR WAY THRU TIGHT PLACES, TRY TO ROUTE THEM SO THEY DON'T RUB OR SCRUB OTHER STUFF

THIS TIME WE INSTALLED NEW--LIFETIME WARRANTY WIRES

I PURCHASED A FEW FEET OF 3/8 FUEL LINE, I CUT THE FUEL LINE INTO VARIOUS NEEDED LENGTHS--SPLIT THEM AND COVERED PORTIONS OF THE PLUG WIRES, EVERY PLACE A WIRE DID OR COULD RUB OR TOUCH ANYTHING.

THAT WAS THE FIX FOR HER!

HOPE THIS HELPS

KEEP US POSTED

THE MEDIC

Wow, that's one major sentence! Without punctuation it can be read three or four different ways, but I was able to determine there is some misinformation there. It sounds like the car was repaired at a Ford dealership. They replaced the harmonic balancer but I don't know why or what the symptom was. When you picked up the car, the Check Engine light was on. The proper thing to do at that point is stop immediately and go back in and tell your service adviser about it. The mechanic deserves the chance to check his work and correct any mistakes. If you wait a day or two, (or even an hour), to go back, the service manager can rightfully assume this is a new problem that just started and has nothing to do with the work you were charged for. You'll be expected to pay for the new diagnosis and repair.

Your comment about the Check Engine light turning on because the battery was disconnected is one I've never heard before. That is exactly backward. If that were true, every car on the road would have its Check Engine light on. There are well over 2,000 potential diagnostic fault codes that can be set related to all the things the Engine Computer monitors. Only about half of them refer to things that could adversely affect emissions. THOSE are the codes that must turn on the Check Engine light. The other half of the codes can be set and you may never know it by the way the engine runs. A lot of people incorrectly assume there are no codes just because the Check Engine light is not on.

One way to ERASE those codes is by disconnecting the battery. That erases all the other things all the computers had learned previously and can make for some minor driveability issues for a few minutes until the conditions are met for those things to be relearned. Those usually occur without you even knowing it.

"everything will be OK then all of a sudden the engine seems to lose power..."

You didn't say what kind of store you went to, but if that was an auto parts store, those people are there to sell parts. Many of them never were a mechanic. You started out with, "everything will be okay", and they told you to check for spark. Logic dictates if the engine is running okay, there has to be spark to every spark plug. Testing for spark won't prove anything. "All of a sudden the engine seems to lose power". THAT is the time testing has to be done because that's when there's a defect occurring that needs to be located.

It probably is not practical to run alongside the car with the hood up while the problem acts up, so we have to try something else. In this case you're fortunate to have fault codes that specify which cylinders are misfiring. We have to consider spark, fuel, compression, and proper timing of all the events. If we are to assume only these two cylinders have problems, we can rule out timing because a problem there would affect all the cylinders and wouldn't be intermittent. While there are some rare exceptions, we can probably rule out compression because problems with that are rarely intermittent.

That leaves spark and fuel. Your engine uses an ignition coil pack with three individual coils. If one of them fires cylinders one and five, that is a good suspect. Also consider the Engine Computer tells those coils when to fire so it is also a suspect. If cylinders one and five are fired by different ignition coils, we can rule those two things out. Ignition coils can be intermittent, but the causes of those failures usually lead to a permanent failure, and therefore one that's easy to diagnose. When a coil-related problem continues to be intermittent, a better suspect is a stretched or corroded pair of terminals in a connector.

At the mileage you listed the spark plugs should have been replaced at least twice already. If they are due for replacement again, start with that. The next thing would be to switch number one and five spark plugs with two from the other cylinders, erase the fault codes, then see if codes set for misfires on cylinders one and five again or for the two cylinders you moved those spark plugs to. If two different cylinders set fault codes, suspect the spark plugs.

The same is true for the injectors. Whoever suggested feeling them to determine if they were clicking doesn't understand much about injectors. They're going to click whether they're passing fuel or not, unless one is shorted. A shorted injector will be detected and a totally different fault code will set. I'm confident that is not what happened here because first of all, that's pretty rare, and second, what's the chance it's going to happen to two at the same time? An injector can become plugged with varnish or debris, but that happens gradually over a long time. That blockage won't magically clear up intermittently either. What IS more likely to occur is a pair of terminals can become corroded in a connector, and those could cause one or multiple injectors to stop firing. Again, that would be detected as an open circuit to an injector and a much different fault code would set. You can identify a bad injector by switching the suspect one with one from a different cylinder, just like we did with the spark plugs. If a misfire code sets for the different cylinder, suspect the injector.

Be aware too that you can get an idea of the severity of the diagnostic fault code by how the Check Engine light acts. With codes related to things that don't affect emissions, the Check Engine light won't be on. With minor problems that are intermittent, the light will go off while you're driving when the problem stops occurring. With more serious problems, if it clears up, the light will stay on until you turn the ignition switch off and restart the engine. For more serious problems, even if it stops acting up, the light will always be on.

By far the most serious problems are when the Check Engine light is flashing. That means too much unburned fuel is going into the exhaust system and is going to overheat and damage the expensive catalytic converter. You're supposed to stop the engine right away.

Dandy. Let me share more details about how your charging system works. Ford is one of the few manufacturers that uses a "stator" or "S" terminal on their generators and voltage regulators. That is tapped off the middle of the output circuitry, and therefore will have exactly half of output voltage when the generator is working. Since way back in the '60s they used that voltage to tell the voltage regulator to turn the dash warning light off. The problem is if you have one bad diode of the six, you will only be able to get a maximum of exactly one third of the generator's maximum rated current. That is not enough to meet the demands of the entire electrical system under all conditions, especially on today's cars with all their unnecessary electronics. But, ... As long as there is SOME output current, the dash light will be off.

Starting in the late '80s Ford progressed to one of the best designs, second only to all of the variations of Chrysler systems. Once the engineers figured out what they had done though they managed to screw it up, so now they're back to systems that are harder to work on.

Where their old voltage regulators turned the warning light off anytime there was SOME output, your electronic regulator turns the warning light on for no output, low output voltage, and high output voltage. I can get into the theory if you want me to, but the simplified version is that low output voltage is caused by a failed diode, so the warning light will be on, and that will cause the maximum output current to be one third of normal. Most commonly your car uses a 130 amp generator, but I'm going to call it a 120 amp unit so I can do the math in my head! With one failed diode, the most current you'll be able to get is 40 amps. That is perfectly fine if the electrical system is only asking for 38 amps. Now turn on the air conditioning, or the heater fan, or the rear window defogger, and the system wants perhaps 50 amps. The battery has to make up the difference until it slowly runs down over days or weeks. There are three output circuits in the generator. Each one produces a pulse of current and they're all spaced equally apart. With the failed diode inside the generator, one of those circuits is dead, so you get a pulse, a pulse, then a missing pulse. During that missing pulse, output voltage drops a lot until the next pulse shows up. The difference between the highest voltage and that dropped voltage is called "ripple" voltage. Normally that is pretty low, and what is there is smoothed out by the battery. By the way, it's that ripple voltage and the 40 amps that professional load testers look at to determine when there's a failed diode.

When you turn on the AC and demand more current than the generator can deliver, the battery makes up the difference and that causes its voltage to drop a little. The voltage regulator tries to bump up the generator's output so the voltage for the two good circuits goes up, but the dead circuit is still dead. Now ripple voltage has increased even more. That is what the regulator sees when it is monitoring the voltage on that "S" terminal. In the past the regulator would have been happy to see something, ... Anything. Your newer design looks at many more things and sees that ripple voltage and interprets that as an inability to generate sufficient current. It doesn't know that the battery is having to make up for the generator's inability to supply enough current. It only sees the result of trying to work harder, and that is what tells it to turn on the dash light when you turn on more stuff.

There's one more oddity you might want to keep in the back of your mind. That excessive ripple voltage causes corresponding surges in current going back to the battery and other circuitry. Current flow through a wire sets up a magnetic field, and a moving, (building up and collapsing) magnetic field will "induce" voltage pulses in any wires in that magnetic field. To say that differently, that high ripple voltage will cause voltage spikes in other wires. This is a real big problem for owners of '87 and newer GM vehicles, even when their generators are working properly, ... Ahh, ... Normally. Those voltage spikes can interfere with computer sensor signals. That can trick the Engine Computer into firing a spark plug at the wrong time. One errant pulse could cancel out the needed pulse from a sensor that tells the computer to fire some of the injectors, ... And guess what that could cause. Loss of power.

In fact, on GM vehicles in particular, but also on all others, when you have an elusive running problem that defies diagnosis, unplug the wires in the smaller connector to disable the generator. If the running problem clears up, suspect the generator.