2002 - Replacing PCM Question

[Sixonemale]

I have 2002 Explorer, 4x4, 4.0 V-6, Eddie Bauer edition with about 174,000 miles on it. I had my transmission rebuilt about a year ago and it shifts perfectly. Recently I have had the OD flash with codes P0755 and P0760 come up pointing to solenoid B & C so I replaced the solenoid block and the codes still come up the OD light flashing. The trans shop said the solenoid is working perfectly and so is the transmission. They did an ohm check on all lines which from the PCM which checked out fine, so they think it's the PCM.

Question: I've looked into replacing a PCM and it does not seem very complicated, but some of what I have read says that the Ford dealer has reprogram the keys, etc. Is that true or can I replace it myself and assume it's plug and play.

My explorer was built in February 2002.

Thanks in advance for all answers.

 

[2000StreetRod]

Pats

If your 2002 has PATS like my 2000 then the PCM will have to be programmed to recognize your keys. Your existing keys will turn on the ignition and in my case allow the starter to crank but the fuel injectors will be disabled. It takes a special machine and about twenty minutes each for the first two keys. After the PCM recognizes two keys additional keys can be "learned" in less than a minute. The vehicle will have to be towed to either the dealer or a PATS qualified locksmith after replacing the PCM. Or to avoid the tow charge, you could get the locksmith to come to the vehicle or change the PCM in the locksmith's parking lot.

The PCMs are fairly reliable and I am concerned that your problem may not be due to the PCM.
P0755 Shift Solenoid B Malfunction
P0760 Shift Solenoid C Malfunction
Unfortunately, right now I can't think of any additional tests that the transmission shop hasn't done to better isolate the source of the problem. Have you tried disconnecting the battery, turning on the headlights for a minute to clear keep alive memory, and then reconnecting the battery to see if the faults return after driving a while?

 

[Sixonemale]

StreetRod,

First off, thanks for feedback. Is there any way that I can detect whether or not my car has PATS?

Secondly, I agree with you that the PCMs are fairly reliable and rarely malfunction and that’s what is bothering me. When I originally had the code P0755 about three months ago, I went to the transmission shop and they test drove it with a computer and everything within the transmission was working fine. Even though the transmission spec’d out I had them replace the solenoid block since that what was what the code was referring to. They replaced the solenoid with another remanufactured one and almost immediately the same code came up again. Another transmission shop took the car for a drive with a computer and said that the trans was working fine and that it was an electrical problem.

I then had my mechanic look under the car and he noticed that condensate was leaking onto a connector to the senor. He dried it out with a compressor and put tape over it and no code showed up for a couple of months, so I thought it was fixed. When it occurred recently, he dried it out and put tape on again, but to no avail.

So, I’m thinking it could be the PCM, but not likely, maybe I need a new solenoid block and not a manufactured one, or I have a short somewhere in the system. I had another transmission shop search for a short as mentioned above, but they could not find one and said that these PCMs go out in about 10 years and it seems to be common. I'm also wondering if the PCM cannot communicate correctly with re-manufactured solenoid.

Frustrating - The last thing I want to do is to take it to a dealer and have them replace parts according to codes that would result enormous costs for a car that is really not worth that much.

 

[2000StreetRod]

PATS implemented in 1999

I think all Fords manufactured in 1999 and later have PATS but there are different versions. If you have a Theft light in the instrument cluster that blinks every 2 seconds when the ignition is off and a chip on your key then you have PATS.

I found this searching the internet for P0755:
"Possible causes
- Low transmission fluid level
- Dirty transmission fluid
- Faulty shift solenoid 2 valve
- Shift solenoid 2 valve harness is open or shorted
- Shift solenoid 2 valve circuit poor electrical connection
When the a transmission solenoid is malfunction, in most cases the problem is not the electrical part of the solenoid; the problem is foreign material obstructing the mechanical function of the solenoid or the flow of the fluid through the transmission valve body. If the transmission fluid is very dirty, it is recommend changing the transmission fluid and if possible removing the transmission pan for further diagnosis. Excessive debris or metal particles on the transmission pan could be an indication that there is a transmission mechanical failure and that the transmission will need to be rebuilt or replaced."

Since the transmission is shifting properly as verified by your driving and the transmission shop then the solenoids must be functioning under the control of the PCM. I think the PCM merely shorts the low side of the solenoid to chassis ground. Maybe there is a higher than normal resistance in the path so the PCM thinks the solenoid has failed. On my Sport the main connector is located behind the block next to the firewall.

Maybe the contacts are dirty or the plug is loose.

 

[Sixonemale]

I’m in agreement with what you have said and what I have read, because I have an anti-theft light that blinks every two seconds, my Explorer does have PATS.

I’ve also done a lot of research on code P0755 and came up with the same information that you did. My transmission fluid was recently changed when the new remanufactured solenoid block was put in a short time ago. And, before that when the transmission was rebuilt within the last 15,000 miles, so I know everything is clean and it’s working properly.

I also agree that since it’s shifting properly that the PCM is working correctly with the solenoids. Thanks for bringing up the connectors, I think that solution is going in the proper direction.

One thing I did not mention because I did not think it was relevant was that AC light does not turn on anymore during the auto cycle, but the system works fine. When the transmission shop was working with it, the AC was turned off and they could not get it to throw a code, but once the car was turned over to me I turned on the AC and half mile from the shop the OD light began to blink. Could a short in the AC cluster cause this? It would seem very odd to me if that is the case. (I just bought the AC control panel on Ebay and am going to replace it for good measure).

Thanks again for your thoughts.