2006 Taurus P0352

Have a 2006 Ford Taurus that has two dead cylinders.
Cylinder 3 and 4. Code says bad coil. I replaced with new coil and plugs. Same problem. Replaced wires and same problem.
Car has 65K. What is causing both cylinders to be dead?
Pulled wires off while running and no spark on 3 and 4. Any ideas would be greatly appreciated.

The diagnostic code does not say "bad coil," a bad coil is one or several possible causes.

Per the factory service manual:

Description: Each ignition primary circuit is continuously monitored. The test fails when the powertrain control module (PCM) does not receive a valid ignition diagnostic monitor (IDM) pulse signal from the ignition module (integrated in the PCM).

Possible Causes:

Open or short in the Ignition START/RUN circuit
Open coil driver circuit
Coil driver circuit shorted to ground
Damaged coil
Coil driver circuit shorted to VPWR

Diagnostic Aids: A P035x diagnostic trouble code (DTC) only sets for a coil primary circuit failure. A secondary ignition coil or spark plug failure does not set a P035x DTC. A P030x DTC does not set for a coil primary circuit malfunction. A P035x DTC may set with or without a P030x DTC; however a P035x DTC sets first.

When this DTC is set, the powertrain control module (PCM) enters failure mode effects management (FMEM) which shuts down the injector for the associated cylinder in order to protect the catalytic converter. This is normal operation; do not attempt to diagnose the injector with this DTC present.

If a primary coil is damaged due to a harness short to ground the powertrain control module (PCM) will not be damaged. Do not replace the PCM with out verifying the coil driver functionality.

Use the 12-volt non-powered test lamp to verify START/RUN voltage at the ignition coil harness connector.
Check the coil driver circuit for open, short to VPWR, or short to ground.

-Rod

Thank you Rod for your reply!
Where is my PCM located?

I'd have to check the service manual this evening to confirm, but I believe it's behind the passenger side kick panel.

-Rod

Thanks Rod!

Solved! It was my PCM. Did a continuity test from coil back to PCM plug. All wires tested fine. So, pulled out PCM and took apart. Found a burnt and cracked chip. Going to buy new PCM from NAPA that comes pre flashed for $322.00.

Good find, and thank you for following up with what you found. Out of curiosity, do you know if the failed component is a capacitor or something else?

-Rod

Here are some pics! Don't think it was a capacitor.
Notice on 3rd picture, the 3rd chip on the left is cracked and looks like it has been very hot.

The group of 3 parts in the 3rd image are transistors. That would make sense as transistors are also known as "drivers". I suppose those three transistors are for each of the three coil primaries. There are a couple of components, one on each side of the three transistors, that also appear to have blown. I'm not sure if those are capacitors, diodes, or possibly even ferrite filters. It definitely looks like replacing the PCM was the right approach. Hopefully those parts were damaged due to infant mortality, or a bad coil which you've now replaced.

I was more curious than anything as to what failed. I don't hear much about Ford PCMs failing so I was curious what the cause of your failure was. I've repaired a few Mitsubishi ECMs due to bad electrolytic capacitors, but yours doesn't look quite so easy to repair.

-Rod

Thank you Rod.
Did notice on the bottom side of the coil on cylinder 3 and 4, there is a crack in the plastic. Not sure if this is what caused the PCM to fail. I replaced the coil as well.