Good day,

2001 Ranger 3.0 liter has developed a transmission casualty. I was driving along at 30 mph and the transmission went into "limp' mode with O/D light flashing and truck will only barely creep along with high engine rpm. When I got the truck home I was able to retrieve a p0720, output shaft speed sensor signal fault. I had hoped that replacing the sensor would solve this casualty.

Of course this was not the case. I have read all the posts I can find for this particular fault and realize that I must electrically trace the continuity of this circuit and also ensure that it's not grounded. I have been unable to find the needed wiring diagrams or pinout information.

Before I have to try and blindly start pawing through the connectors I'm here asking if someone could provide me with the pinout for the PCM and perhaps the bulk connector above the engine between the PCM and the transmission wiring harness. Thanks in advance for anyone who can help. I am also keen to hear of any diagnostic tips that I may have overlooked.
Again, thanks to all in this forum.

 

The following is from my 2001 Service Manual:
P0720 Component OSS, Insufficient input from OSS sensor, PCM detedted a loss of OSS signal during operation, harsh sifts, abnormal shift schedule, no torpue converter clutch engagement,
Check resistance at TSS, and ISS or OSS sensor.
Resistance as follows:
TSS 64-126
ISS 325-615
OSS 305-735
TSS measurements taken at inside top leads
If resistance measured out of specification, replace sensor.

 

I appreciate your post. I have already replaced the sensor ,as a quick fix, however, it didn't repair the tuck. I must now "ohm out" the wiring from the OSS sensor to the PCM. I was just hoping to get the connector pin numbers so I don't have to search by color. Thanks for your reply anyhow, might come in handy down the line.

 

From what I can tell, on your '01 the OSS sensor (DB/YE wire) is at pin #84 on the PCM.

The signal return (GY/RD wire) is at pin #91.

 

Thanks Rockledge, that's precisely the information I need. I shall set to it in the morning.

 

It rained yesterday so I got out this afternoon to work on the casualty. I disconnected the negative battery cable then the PCM connector, There was no numbers on the face except for the part number and a Ford logo. I counted the rows of 13 pins until I came to #s 84 and 91. I was able to see between the harness and connector body that pin 91 is indeed a greywire with a red tracer. This partially confirmed I was on the correct pins so I cut a paper clip in two and inserted them into the respective recepticles and measured 390 ohms. Well within g k50's supplied threshold value of 305 - 735 ohms for the OSS sensor. Uh oh...

I crawled beneath the truck and disconnected the sensor and the meter then another test of same pins read infinity. A check to ground revealed infinity on the signal wire and approximately 1.2 K 0hms to battery negative cable and pin # 91.

Since this confirms that my OSS circuit sinal is correct I am curious if the signal return should be 1200 ohms? Of course, I had the connector out of the PCM so perhaps the ground path is made up within the module?
I'm also concerned that it could be the transmission at fault?

When I crank the truck and shift into drive it engages with a light bump and then does nothing, a racing engine is all. When in 1st or 2nd a high rpm will result in a creeping forward and reverse will do the same rearwards. This reulted in the O/D light flashing and a check gage light staying on. Thanks again for your time and your advice,

Tom

 

Right, you need to plug the connector back in and then "back probe" the sig return wire. As shown

 

You said you were able to pull the p0720 code. Was that done using a standard OBD code reader? The reason I ask, is that it's possible for tranny codes to be stored in memory that a basic OBD unit might not be able to read.

 

Pardon my delay due to rain and other commitments. I really appreciate your instructions Rockledge. I was able to back-probe the OSS return wire as there was an opening in the back-shell of the PCM connector. I inserted a paper clip into the back of pin # 91 and it now measures 0 ohms to ground with the PCM connected. As stated earlier, I now know the wiring of the OSS circuit is complete and the signal wire is not shorted to ground. Of course this creates more questions (to me) than it answers.

The scan tool I used was a UIF Tech MemoScan c100

http://www.onboarddiagnostics.com/download/c100.pdf

As pages 13 & 14 shows all manners of transmission fault codes, I believe (please correct me if I'm wrong) the scanner is capable of pulling whatever codes have accrued as far as the power train is concerned? I will be borrowing the scanner again tomorrow to see if any other codes have popped up.

Since I have time today (and clear weather) I'm going to make sure I haven't missed anything obvious- blown fuse, etc. Thanks again and I welcome ANY advice or suggestions. I need to get this truck running to earn some steady income.

 

I checked all fuses, none were blown. I also checked the PCM relay and diode and their bases for sign of corrosion. All appeared clean and bright, so I gave them a shot of contact cleaner anyway. I failed to mention the shift selector's somewhat cockeyed so I'll go ahead and align it.

 

had same problem with my 99,, it turned out to be a broken wire to the right front sensor behind the brake caliper,,, on my ranger there are 3 sensors one on each front wheel and one on the back axle,,,,,,,,