Ford Taurus won’t start
If you run into a situation with a Taurus no crank condition or any kind of Ford no crank, follow the tips in this post. I’ve included a typical starter wiring diagram to show how complicated this starter system really is. And it’s another example of why it drives me crazy when people post questions like, “car won’t start” on automotive forums.
Let’s take a look at this system. At first glance, diagnosing a Taurus no crank condition isn’t much different that diagnosing any other vehicle. You start by checking for battery voltage on the “S” terminal at the starter while turning the key to the START position. That’s what sends battery power to the starter solenoid. If you get battery power on the “S” terminal, you confirm that the power is flowing from the fuse to the IGN switch, from the IGN switch to the park/neutral switch (called a transmission range selector in some Fords), and then to the starter motor relay in the underhood fuse box. If you see battery voltage at the “S” terminal but the starter doesn’t engage, check for battery voltage on the large cable coming from the battery. If you see battery voltage, the starter solenoid or starter motor is bad.
If you don’t get battery voltage at the “S” terminal, you could be looking at several issues. You can see from this wiring diagram that the starter gets “S” terminal power through the starter motor relay. So your next step is to yank the starter motor relay and check for battery power on the incoming power wires to the relay contacts and the relay control coil. Battery power should be available on the contacts at all times and on the control coil when the key is turned to START.
Next, check for ground on the starter motor relay control coil. The PCM provides ground to the starter motor relay control coil when it sees power flow through the park or neutral position on the transmission range selector and in some case, power coming from the brake pedal position switch. At that point the PCM knows that it’s safe to operate the starter.
But notice that the PCM also has a power relay and at least one fuse. In fact, the PCM has at least two fuses. If you’re not getting ground from the PCM, check the PCM power relay and the power relay fuse. If those check out, next check for proper operation of the transmission range selector and the IGN switch.
An easy way to check the IGN switch is to operate the fog lamps and headlights when the no crank condition is present. If the lights illuminate, the IGN switch is working. Next, check for trouble codes with a code reader or scan tool. If you get a no communication, that could mean a faulty PCM OR a bad PCM fuse or bad power relay. Check those first before replacing a PCM
©, 2015 Rick MuscoplatPosted on by Rick Muscoplat
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