Red LED in dash killing my car

Driving around today it happened twice. I was in 4th-5th gear and the lil red blicking led that is normally off when the car is on...came on and stayed lit for about a second or two, and when that happened my car lost power. The power didnt go out, but my rpms would start to drop. It happened twice tonight. The only thing I heard that the LED was affiliated with was the PATS system. Any hints clues or suggestions or things to check? Thanks

How old is the battery or alternator? Test it.
http://www.contour.org/ceg-vb/showthread.php?t=3535

How does the wiring harness look?

Also how old is the battery in the key FOB?

I just fixed this problem on my car.. lasted (PLAUGED) me about 8 months. Started out being once or maybe twice a week... then a day.. then every two or three minutes. Eventually I could even MOVE the car because it happened every second, twice or three times a second.

My symptoms:

• CEL light would "flicker", or sometimes STROBE very rapidly.
• PATS light would illuminate and do a 1 second "prove out" test, as if you just turned on the ignition.
• tach would drop/dive towards 0
• car power wasn't affected.. radio, lights, etc, remain
• fuel and spark were GONE during that time. no acceleration, no idling (when it got worse, that is).. nothing..
• voltage at the BATTERY wouldn't move.. would drop from 14.2 to 13.7-ish but that was only because the engine wasn't turning over any more and the alternator stopped producing power, for a second..

I checked everything. PCM power.. battery power.. IGNITON ITSELF (jumpered around the ignition to prove it wasn't the problem)
searched for loose grounds.. everything

The problem? a bad TPS wiring connection.

The TPS was fine.. the WIRING harness to the TPS was shorted, from the positive supply to the ground, which is a shared supply for a lot of the rest of the wiring harness, including the gauge cluster, the ignition, and the pats power.

Never in a million years would ANYONE that I told, or asked help from (on CEG, etc) have imagined that something related to the TPS would cause such EXTREME symptoms.

What should you do?

Check ALL of your grounds in the engine bay.

under the battery/fuse box
at the firewall on the passenger/center side, everywhere.
check the negative wires that go to the battery, and make sure they aren't loose in the crimped on ring that attaches to the battery.

then... the next time it is doing this, repetitively (if it gets worse and more frequent), unplug the TPS from the throttle body.. I bet it smoothes out and stops.

Hey Ray,

That signal was the Vref signal that was shorting to signal ground.

I've seen another case in which Vref was constantly shorting to ground. Completely killed the system on that vehicle until the short was removed/repaired.

The PCM tends to get pretty cranky (as you found out) when this signal gets shorted.

On the SVT, Vref is only distributed to the TPS and the DPFE/EPT sensor for the years I checked. The OP didn't indicate what year he has....

Steve

Thank you for the clarification. Also, just to be clear to the OP.

This is not a PATS (Passive Anti Theft System.. ie.. the red led) problem. PATS illuminates the LED for one second when you first turn the key on. This is a prove-out test that is indicating that the signal in your key is accepted, and the car is allowed to start. PATS does not actively check this once you start the car. You can unplug PATS from the ignition once you start the car and you are fine.. until you shut the car off, again.

The presence of that flashing led is not actually PATS, but something causing PATS to lose power and do the prove-out test, again.

As stated, above, check all grounds and the TPS/DPFE/EPT connectors. Simply unplugging them one at a time will remove any shorts in that connector. If your car begins to do this frequently enough (like mine.. every half second!!!) you will have no problem determining if it was your problem when you unplug a sensor. If it is still only doing it rarely, then how can you tell, right? Still, check the sensor/connector for looseness, or bent/burnt looking pins.

Thanks for the replies. I will start checking the wires.

Tony: Brand new (few months old) battery (optima) and alternator (new oem).