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

10 Replies

Tiny
JOE F
  • 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
JOE F
  • 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
JOE F
  • 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
JOE F
  • 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
JOE F
  • 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

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