Transmission downshifting problem

[las59]

Originally Posted by behlinla

If you're seeing dropout on other sensors then that's a good indication you have a problem with the 5V reference voltage used for the sensors. It could be the PCM but you have to rule out the wiring first.

Check for 12V on PCM pins 55, 71, and 97. Check for good grounds (0 volts) on pins 25, 24, 51, 76, 77, 103, and 33. You have a Windstar so I'm not sure of the ground locations, but there is usually one near the PCM. I suggest cleaning it.

The ground by the PCM is the one I cleaned earlier.

I also forgot to menttion that with the used MAF sensor installed I was getting a P0102 code.

I do have the Electrical Vacuum and Troubleshooting Manual for the vehicle also, so that helps finding the grounds and pin locations you have provided to check.

Should I remove the connector on the PCM to check or backprobe the pins?

thanks again behlinla

[behlinla]

If you have the diagrams the grounds are G105, G103, G200. I don't have the diagrams so can you tell me which one you cleaned already?

Backprobe at the PCM connector but leave it connected (testing requires the key to be on and the PCM to be powered).

[las59]

Originally Posted by behlinla

If you have the diagrams the grounds are G105, G103, G200. I don't have the diagrams so can you tell me which one you cleaned already?

Backprobe at the PCM connector but leave it connected (testing requires the key to be on and the PCM to be powered).

I cleaned G105.. The wire goes into the wire bundle that goes towards the PCM, and the other wire (braided copper cable) goes to the engine block underneath the alternator. When I removed the cable and cleaned the eyelet and block the cable did have some green corrision on the outside. I did not ohm test the cable. I have planned on replacing thecable in the future. Do you think I should replace now??

[behlinla]

Focus on cleaning the other ground first then you can come back to it. I would test it before replacing it so you have an idea if that's the problem or not.

G103 is another big one (what the MAF ground goes to), so find/clean that one next.

[las59]

OK I cleaned the G103 ground the other day. I have not yet checked and cleaned the ground by the PCM under the cowl (Case Ground) or the ground by the glove box.(G200)

I did get another used MAF, installed it and it did run and was driveable but again it threw the P0102 code, so I installed the original MAF again. I know it is driveable and dependable for the wife to drive as here health is not great.

I do not underrstand why I get the P0102 code with the MAF I just got but not with the original MAF.

Hopefully the weather will cooperate so I can remove the cowl and do the testing at the PCM that behlinla suggested.

edit: Original MAF shows 3.70 gm/sec, 1st used MAF showed 0.00gm/sec and 2nd used MAF showed 0.11 gm/sec. if that means anything.

Any thoughts on the reasoning of the P0102 code.

[behlinla]

Originally Posted by las59

Any thoughts on the reasoning of the P0102 code.

You got two used POS MAF sensors. Where are you getting these things? You should be getting these off cars at a junkyard (remove yourself) or buying a new one. If someone is selling their MAF sensor individually there's probably a good reason why (like it failed and they want money).

3.70 g/sec is a normal reading at idle, the other two aren't.

[las59]

That is what I fiqured you would say. At this timeI really can not afford to spend $100 on a new and I do not know anyone with a 3.0L Windstar. I will call around Monday to see if any JY has a one. 3.0L engine in a Windstar is not very common.

I am getting them on ebay with a warranty.

I will see what weather is like tommorrow. probably pull the cowl off and do the PCM tests.

[las59]

Originally Posted by behlinla

If you're seeing dropout on other sensors then that's a good indication you have a problem with the 5V reference voltage used for the sensors. It could be the PCM but you have to rule out the wiring first.

Check for 12V on PCM pins 55, 71, and 97. Check for good grounds (0 volts) on pins 25, 24, 51, 76, 77, 103, and 33. You have a Windstar so I'm not sure of the ground locations, but there is usually one near the PCM. I suggest cleaning it.

Today I did the testing.

Pins 55. 71, 97 all have 12v

24, 25, 51, 76, 77, & 103 have 0.036V, forgot to do #33.

Original MAF sensor Gound 1.09V, and ground return 1.09V.

Does this mean that the sensor has a short and return voltage is going thru the sensor? Would cutting the ground for the MAF and hooking it up directly to the battery negative do any good?


I did get a 4 gauge battery cable and attached it to the negative battery post and a long threaded stud on the Upper intake manifold.

I have not gotten a new sensor, wanted to wait for testing of PCM.

Thanks for advice.

EDIT:
Yesterday when I had the laptop hooked up again I stopped at a store and disconnected the software by hitting the disconnect button. When I returned and pushed the connect button the
software would not communicate with the PCM. I tried several times. Finally I completely disconnected the tool and hooked up my cheap code reader to see if it would communicate and it worked. I then reconnected the laptop and it did communicate with the PCM. This did happen once before since dealing with the used no functional MAF sensors. I have not tried the laptop with any other vehicles since this has occured so I am not sure if it is the software or the PCM.

[behlinla]

Okay, the PCM voltages and grounds look good.

However, the ground voltage on the MAF is too high. It should be less than 0.1 volt. The MAF ground goes to G103, and since you cleaned that I think you have a problem somewhere between the MAF and G103. It's the black/white wire.

The MAF signal return (tan/light blue wire) may have some voltage on it, so I would leave that alone for now.

So again, you might trace that black/white wire from the MAF back to G103 to see if you can find the bad connection.

The scan tool not connecting does not necessarily mean the PCM is bad. It could just be the scan tool software especially if it's an advanced scanner that supports Ford-specific PIDs (something like a Snap-on tool).

[las59]

I took the ground cable from battery to (G103) located on the stud radiator side of transmission according to the wiring Ford manual I have., acutally completely removed the stud and cleaned tranny area and stud bolt, nut, cable end again. No wires at this location except battery cable.

Tested the ground (blk/w) wire at the MAF sensor, Key Off Engine Off 0.000V. Engine running I get 0.085V at blk/w wire and 0.085V at tan/lt.blue wire. Correct me if I am wrong but doesn't this mean the black/white wire is good??

G105 is located on the passenger side, on the body, with a ground strap going to the engine block.

Edit:

There is also a black wire that comes out of the wiring harness to the ecu that is also grounded at the G105.

I do not want to start removing all the tape on the wiring harness if not necessary is why I ask.

thanks