Multi pin connectors

Tiny
QFONG
  • MEMBER
  • 1995 MERCURY MYSTIQUE
  • 2.5L
  • V6
  • 2WD
  • AUTOMATIC
  • 131,000 MILES
When looking at a wiring diagram and seeing a many-pin connector, are you looking at the front side or the wire side, male or female part? For instance, Alldatadiy schematics.
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Thursday, January 13th, 2022 AT 5:38 PM

38 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

The connector pins are from the front, male or female connector. Is that what you mean?

I attached a connector picture of the ECM for your vehicle below. That is with the connector disconnected and you are looking into the connector.

Let me know if you have other questions.

Take care,

Joe

See pic below.
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Thursday, January 13th, 2022 AT 8:29 PM
Tiny
QFONG
  • MEMBER
Am I looking into the ECM or the plug?
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Friday, January 14th, 2022 AT 7:49 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
That is the ECM. In most cases when it is a connector, wiring is shown at the connector. I don't want to say all the time, but most of the time. See pic 1 below.

By chance, is this the vehicle in Florida? Let me know. Sorry to ask, but I just remembered a vehicle similar to this being there. LOL

Let me know.

Joe
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Friday, January 14th, 2022 AT 7:49 PM
Tiny
QFONG
  • MEMBER
Yes, this is the 1995 Mystique from last year in Florida. I'm a snowbird so I'm here for 4 months every year.
The engine is running well now but the transmission is not doing too good. In "D" I have nothing. In 1 and 2 and "R" I get solid engagement. I need a way to electrically test to see if the signals are there.
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Saturday, January 15th, 2022 AT 12:34 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I had a feeling that it was you. LOL Welcome back and boy do I wish I was in Florida. It's 20 degrees here and waiting for a bad snowstorm tomorrow. Ugh!

Regardless, when you place it in drive, does the indicator show D? I ask because I'm questioning if the transmission range sensor is bad. Here is how it works.

The transmission range sensor has six separate resistors in series. Each resistor has an output connection corresponding to a transmission position (P, R, N, D, 1, 2).

The PCM applies a 5.0-volt reference signal to the TR pin 30. The signal return circuit, pin 46, supplies a ground path to the sensor. As the transmission is shifted, the TR sensor output wiper arm moves to a corresponding resistor connection (based on gear selection). The six inline resistors provide a separate voltage drop for each transmission position. Based on the voltage signal, the PCM identifies the current transmission shift lever position.

So, I suspect that either the TR has failed, the linkage isn't fully placing the TR in the drive position, or there is an electrical issue. However, if there is an issue within the circuit, I wouldn't think it would be limited to just reverse.

If you look below, I attached the diagnostics for testing. Pic 1 indicates the use of a breakout box, which most people don't own. Since that is the most likely case, you will need to check the return signal resistance at the PCM or the sensor itself.

Pic 2 shows the resistance based on gear selection. Pics 3 and 4 provide the location and directions for removal and replacement. Pic 5 is a pinout of the PCM. I highlighted the pins involved. Pin 30 provides the 5v reference and pin 46 is the signal return pin.

Since the vehicle sits a lot, you may want to confirm there isn't a corrosion issue on the connectors as well.

I hope this helps. Stay warm and let me know if you have other questions.

Take care,

Joe

See pics below.
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Saturday, January 15th, 2022 AT 2:36 PM
Tiny
QFONG
  • MEMBER
Back in New Hampshire it was around minus 10. Glad to be in FL.
I checked the TR resistance and in each position the resistance was within the range. How would I check the ECM to see if it is functioning properly? I have the unit out and sitting on top of the engine. I can remove the 60-pin plug easily.

Putt
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Monday, January 17th, 2022 AT 1:39 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I thought 20 degrees was bad. No thanks to the neg 10.

I need you to check pin 30 for a 5v reference from the ECM. Also, did you confirm a ground path via pin 46?

Note: I accidentally highlighted the wrong pin above. It should be pin 30 (not 39) that provides power. Also, if you haven't already, disconnect the connector at the ECM and inspect it for damage or corrosion.

As far as testing the ECM, see if there is power and ground for the circuit. If there is, it's good. If there isn't, check wiring between the sensor and ECM for continuity.

Let me know.

Joe
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Monday, January 17th, 2022 AT 5:07 PM
Tiny
QFONG
  • MEMBER
The voltage reading between pin 30 and pin 46 is 4.5v. I checked the resistance of the VSS- 7.8 ohms, TSS-.8 ohms. I'm stumped.
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Tuesday, January 18th, 2022 AT 1:03 PM
Tiny
QFONG
  • MEMBER
Would I be able to put 5v LED bulbs in series with the control wires that go to the transmission to see if there is anything happening?
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Tuesday, January 18th, 2022 AT 1:11 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I don't see why that wouldn't work for testing.

Let me know the results.

Joe
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Tuesday, January 18th, 2022 AT 1:19 PM
Tiny
QFONG
  • MEMBER
The testing went well, so I decided to go out for a drive. The transmission doesn't seem to know what gear it should be in. It jumps around between gears unless I shift manually but it never goes into OD (light off). What tells it to shift?
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Monday, January 24th, 2022 AT 2:41 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Shifting is controlled by the powertrain control module (PCM). The PCM uses information from the speed sensor, throttle position, engine load, speed, and so on.

If the vehicle is shifting erratically, it could be the speedo drive gear, a problem with the fluid itself, or within the valve body. See pic 1 below.

I can't remember, but was line pressure tested? Have you noticed anything related to the speedometer? I likely already know the answer to this, but is the fluid clean and full?

Let me know.

Joe

See pic 2 for a better description of how it works.
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Monday, January 24th, 2022 AT 4:57 PM
Tiny
QFONG
  • MEMBER
I changed the trans fluid last year and added some trans medicine. The car has not been driven in the last 5.5 years so I'm wondering if the solenoid valves have become sticky. Just before the car died in 2016, the trans was fine.
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Monday, January 24th, 2022 AT 5:10 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

You could remove the valve body and inspect it. There are shift solenoids that may be sticking, but that should set a diagnostic trouble code.

Let me know your thoughts. I'll help in any way I can.

Joe

PS: I hope you are enjoying Florida. I have to go plow my driveway now but will be back soon. LOL
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Monday, January 24th, 2022 AT 5:16 PM
Tiny
QFONG
  • MEMBER
Hi Joe, I read something about flushing the transmission with diesel fuel. I guess there are places that do it. What do you think?
We are having bad weather in Florida, low 50s and rain. Still, it beats NH though.

Putt
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Tuesday, January 25th, 2022 AT 3:03 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I'm not too sure about that one. If there is a place, will they guarantee it will not damage the system? I know in the old days; people would do that with their engines to clean it out. It worked as far as I know. However, I never heard of it with a transmission. I suspect for a very short period of time; it would lubricate enough to prevent damage. Just don't drive it long like that.

You know, 50 degrees sounds good. LOL Tonight we're down to 2. I love PA. LOL

Take care,

Joe
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Tuesday, January 25th, 2022 AT 4:55 PM
Tiny
QFONG
  • MEMBER
I decided not to do the diesel fuel flush because I can't see how you would get all the fuel out without flushing with a lot of transmission oil. I'll just change the oil again.

Putt
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Tuesday, January 25th, 2022 AT 5:55 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I'm glad to hear that. LOL I was questioning it. Let me know how things turn out for you.

Joe
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Tuesday, January 25th, 2022 AT 8:57 PM
Tiny
QFONG
  • MEMBER
Hi Joe, I ran into a new problem with the engine. On Monday I drove around for about 45 minutes with an erratic transmission. Then Tuesday I started it and it idled roughly for about 15 minutes and it quit running. Would not restart. The next day I tried my spare ECM and the same thing. The fuel pump was still working normally. Seems like a little heat shuts it down. A lot of black soot comes out of the tail pipe when I rev it.
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Wednesday, February 2nd, 2022 AT 7:07 PM
Tiny
QFONG
  • MEMBER
Couldn't find a reply.
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Wednesday, February 2nd, 2022 AT 7:40 PM

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