Code P0705 & Now PO708on a 4R100 with OD

lswartz · #1 (**permalink**) 06-29-2009, 09:40 AM

Back in December I got the code PO705 & replaced the transmission position sensor Motorcraft # SW5713. Now I am getting PO708 which seems to indicate the same problem. It still seams to be working as it only starts in park & neutral.

Did I get a bad part, put it in wrong, or do they just fail?

Another issue that might be related is the speedometer cable (It might need to be replaced). We took a trip pulling our travel trailer to Shenandoah National Park this last week & it would drop to 45 mph even though we were at 65 mph. It stayed at 45 for quite a long time going & only for a very short time on the way back. Rust has been a problem on this van, replaced rear heater lines (radiator too) & brake lines due to rust. I am thinking I have a rust problem with the cable too.

lswartz · #2 (**permalink**) 07-04-2009, 12:21 PM

Guess I'll try taking taking it off & reinstalling it, might get lucky.

Mark Kovalsky · #3 (**permalink**) 07-04-2009, 01:50 PM

The codes don't necessarily mean that the sensor is bad. It could also mean that the wiring to the sensor is bad. The PCM can't tell the difference.

lswartz · #4 (**permalink**) 07-06-2009, 08:50 AM

Quote:

Originally Posted by Mark Kovalsky

The codes don't necessarily mean that the sensor is bad. It could also mean that the wiring to the sensor is bad. The PCM can't tell the difference.

Thanks, that is a good point. Is there any way to tell or should I pay a visit to my friendly Ford Dealer?

Mark Kovalsky · #5 (**permalink**) 07-06-2009, 03:12 PM

You can electrically check the circuit for opens and shorts. If you don't know how it may be worth a trip to someone that does it for a living.

lswartz · #6 (**permalink**) 07-06-2009, 09:23 PM

I was afraid of that. Too bad you don't live closer to MD. I did pull the sensor off today & don't see any way to put it in wrong as the neutral position on it is clearly marked. I think I will drive it until it throws a code again & go see my Ford Dealer.

Thanks.

lswartz · #7 (**permalink**) 07-23-2009, 08:13 AM

I took it to the local Ford dealer yesterday & they want to replace the PCM for another $622 ($120 to tell me what is wrong). Looks like a PCM is the same as the engine control computer (calibration code 8-96E). Since it is 11 years old Ford doesn't make the part amymore & I have found one from Rockauto (made by Cardone) for $234. I am thinking about putting it in myself - could this be a bad idea?

I am headed out to look at a manual in a couple hours to see how hard it is to get to.

Mark Kovalsky · #8 (**permalink**) 07-23-2009, 01:24 PM

I think the PCM is a longshot for being the cause of the problem. While they do fail at times, it's rare. Wiring breaks MUCH more often.

lswartz · #9 (**permalink**) 07-27-2009, 11:25 AM

That makes more sense to me. I wish I had asked if they had really checked the wiring 1st. I have driven it 2 days & no check engine light. We are off to the beach Thursday with the travel trailer so I'll see if it comes back. It came on the last 2x in about 25 miles.

I am wondering about this Dealer's repair though. They say that Ford no longer makes the part & is only available as aftermarket not OEM. I found the Ford part # F7PZ12A650BMA online at the auto craft shop at Aberdeen Proving Ground & it is available.

suzuki0702 · #10 (**permalink**) 08-01-2009, 06:32 PM

trace the wiring back to the main harness off of the trans sensor and check for continuity. its real easy. tie a lead on one end so its long enough for you to be near both wires. im goin with mark on this one, i had a problem similar with my abs sensor on my 95 half ton! good luck!!

lswartz · #11 (**permalink**) 08-03-2009, 07:01 AM

Thanks. I think both of you are correct on this one. I'm going to try with the Ford Dealer one more time today.

lswartz · #12 (**permalink**) 08-04-2009, 07:55 PM

I struck out with the local ford dealer, called 3 times & the service rep doesn't call back.

I borrowed a multimeter & it looks easy to test continuity. However, there sure are a lot of wires on the PCM end. Plus there is a boot cover that I haven't tried to take off yet either. I'm going to start early tomorrow & try to match the colors of the wires at the position sensor end with the PCM end. Imagine being color blind & trying to do this

.

*crosses fingers & hopes for the best*

lswartz · #13 (**permalink**) 08-20-2009, 04:43 PM

Things went from bad to worse

One wire I could not find at the PCM & 2 I could not seem to get a reading on. Maybe 1 wire is bad but not 2. 2 others tested OK, then they didn't & finally were OK again. I guessed that maybe Ford was right & I needed a new PCM - they were wrong. Guess I had 2 bad wires after all. Then I noticed a transmission leak. $495 later there is no leak but I still have a code PO708. I am fed up with it. I hate to say it, but I have a clunker at 84,000 miles & am going to trade it asap.

Thanks for the help & advice. I really wish I would have persisted a bit longer checking those blasted wires.