Short answer: on a 2007-2014 Ford Edge or Lincoln MKX, a PCM replacement goes wrong for three reasons, and none of them is the new computer. On 2007-2008 models with the 3.5L built on or before March 1, 2008, Ford ties damaged ignition coils to the PCM, so the coils must be checked and replaced along with the computer or they can damage the new one. After any PCM swap, the anti-theft system (PATS) has to accept the new PCM, and the six-speed transmission's solenoid body data has to be in it. Check those three things, and the wiring, before you blame the replacement.
"Replaced the coil and it melted again", "replaced the PCM and the fault came back" and "new PCM, won't start" come up again and again on Ford Edge and MKX forums. This guide uses Ford's own service bulletins and messages, plus cases owners have posted, to explain what is going on and what to check.
Why coils and the PCM fail together on the 2007-2008 models
Ford's technical service bulletin 12-8-17 (August 2012) covers 2007-2008 Edge and MKX models with the 3.5L built on or before March 1, 2008, along with several other Ford, Lincoln and Mercury cars with the 3.0L or 3.5L. The bulletin describes a check engine light with ignition coil codes P0351 to P0356 stored in the PCM and one or more damaged coil-on-plug units.
The bulletin's procedure:
- Read the stored codes. If no P035X code is present, the bulletin does not apply and normal diagnosis follows.
- Remove all the coil-on-plugs and inspect them for cracks or heat damage. If none are damaged, the bulletin stops there.
- If coils are damaged, replace the PCM, all six spark plugs and all six coil-on-plugs. Ford lists a coil, spark plug and intake gasket kit for the 3.5L and a labor time of 1.8 hours on the Edge and MKX.
The bulletin says nothing about programming or keys. Ford revised it later, so a dealer checks the current version against your VIN.
Real cases from owners
- 2007 Edge, coil only: one coil melted, and the owner replaced that coil and the plugs. The new coil melted too, after about five miles, and the car would no longer run.
- 2007 Edge, the full repair: a dealer replaced all the coils, all the plugs and the PCM, the same parts Ford's bulletin lists.
- 2007-2008 Edge 3.5L, original PCM repaired: a failed coil damaged the PCM's driver for that cylinder. The dealer quoted about $2,500 for a new PCM, coils and new keys. The owner had the original PCM repaired instead, fitted new coils and plugs, and kept the original keys and remote start working.
- Lincoln MKX, PCM replaced again and again: the owner's PCM was replaced more than once and the fault kept coming back. Another member, whose powertrain and ABS modules had both been replaced while the warning lights stayed on, reported that the fault only went away when the dealer checked the harness: it was the wiring.
Two lessons come out of these threads. Replacing a coil without dealing with the PCM can kill the new coil, and replacing a PCM without dealing with the coils or the wiring can kill, or fail to fix, the new PCM.
The codes to know
- P0351 to P0356: the ignition coil codes, one for each of the six coils. On 2007-2008 models built on or before March 1, 2008, together with damaged coils, they lead to Ford's bulletin 12-8-17.
- P161A after a PCM replacement: Ford's special service message 46900 links this code, with a no-start and the check engine light on, to an incomplete PATS parameter reset. See Step 4.
- P06B8, P068A or P2610 right after programming: Ford's service article 44707 for 2009-2015 vehicles says these can set if the key is not left off for 30 seconds after PCM programming. See Step 6.
Step 1: Read the codes and look at the coils
Before anything is replaced, read every stored code and note the build date of your Edge or MKX (a dealer can confirm it from the VIN). On a 2007-2008 3.5L built on or before March 1, 2008 with P0351 to P0356 codes, pull the coils and look for cracks or heat damage, as Ford's bulletin does. If a coil is melted or cracked, plan to replace all six coils and plugs with the PCM.
Step 2: Check the wiring and grounds
The MKX case above is a reminder that a PCM which "keeps failing" is often not the problem. If a replacement PCM brings the same fault back, have the harness, connectors and grounds checked before a second computer goes in.
Step 3: Match the replacement PCM
Ford's basic part number for the PCM is 12A650, and the full part number is printed on the label of your old PCM (for example 7T4A-12A650-GE on a 2007 Edge). Ford's bulletin itself says the PCM part number needs a catalog lookup. Use the full number from your label and your VIN to order, so the replacement matches your engine, drive and year.
Step 4: PATS has to accept the new PCM
Ford's SecuriLock Passive Anti-Theft System (PATS) only lets the engine start with a key coded to that vehicle. A replacement PCM has to be introduced to it.
Ford's special service message 46900 describes the case owners keep posting about: a no-start with the check engine light on and code P161A after a PCM replacement, caused by a parameter reset that was not completed. The fix in that message is the PATS parameter reset, done with Ford's diagnostic software (IDS or Ford's J2534 software). According to Ford, the reset transfers the existing key information between the modules, two programmed keys do not have to be present, and the keys do not need to be programmed when only the PCM is replaced.
Ford also notes on its SecuriLock page that non-Ford aftermarket remote start systems are not compatible with PATS and can cause starting problems.
Step 5: The transmission data lives in the PCM
The Edge and MKX six-speed automatic (6F50 or 6F55, depending on model and year) has a solenoid body with its own identification number and strategy number. As Ford's workshop manual is quoted on the Ford Edge Forum, that data has to be downloaded into the PCM, including into a new PCM after a replacement, and data that does not match the transmission can cause driveability problems or transmission damage.
Step 6: After programming, follow Ford's 30-second rule
Ford's service article 44707 covers 2009-2015 vehicles that show the check engine light with P06B8, P068A or P2610 after PCM programming. Ford says these codes can set if the key is not left in the off position for 30 seconds after programming. If they appear, clear them and retest. Ford says plainly: do not replace the PCM for them.
Should you repair your original PCM?
Owners on the Ford Edge Forum like repairing the original PCM when it is repairable, because it already matches the car. The owner in the case above kept the original keys and remote start working that way. Either way, replace damaged coils, because the threads above show what a bad coil does to a PCM.
When the PCM really is the problem
If the coils are good, the wiring and grounds check out and the fault stays, the PCM becomes a real suspect. Then the replacement has to match your vehicle, carry your transmission data, and go through the PATS step.
Frequently asked questions
Do I need to replace the coils when I replace the PCM on a 2007-2008 Edge or MKX?
If the coils are damaged, yes. Ford's bulletin 12-8-17 replaces the PCM, all six coils and all six spark plugs together on affected 2007-2008 models built on or before March 1, 2008.
Will my keys still work after a PCM replacement?
According to Ford's special service message 46900, the PATS parameter reset transfers the existing key information to the new PCM, so the keys do not have to be programmed when only the PCM is replaced. The reset itself is done with Ford's diagnostic software.
Why won't my Edge start after a new PCM?
The case Ford documents in its special service message 46900 is an incomplete PATS parameter reset, which leaves a no-start with the check engine light on and code P161A. A shop with Ford diagnostic software completes the reset.
Why does it shift badly after the PCM was replaced?
On these models the transmission's solenoid body data is stored in the PCM. According to Ford's workshop manual as quoted by owners, data that does not match the transmission can cause driveability problems.
Is there a recall for the Edge or MKX PCM?
We found no NHTSA recall for the PCM or ignition coils on 2007-2014 Edge and MKX models. Ford addressed the coil and PCM problem on 2007-2008 models with technical service bulletin 12-8-17.
Ford Edge and Lincoln MKX PCMs from NPC Automotive Computers
Every NPC unit is remanufactured and programmed before it ships, and NPC loads the six-speed transmission's solenoid body data into the PCM. Order with your VIN and the part number from the label on your old PCM. If your vehicle is PATS (Passive Anti-Theft System) equipped or has a computer chip in your key, you may need to have the keys reprogrammed by a locksmith or Ford dealer after install. If you would rather keep your original PCM, NPC also repairs and returns it. Either way, check the coils first, as described in Step 1. Not sure which PCM fits? Call us before you order and we'll check it with you.
