Trans. Only in 4th gear. Why?

[Dead Civic]

I'll preface this with the fact that I went through a transmission intercooler failure.

CEL P0751.
I've replaced:
*the solenoiaolenoids
*Trans filter
*Oil
*TPS

I can select the gears (3,1-2) and they work fine. 1-2 down shifts... A little late but it does.

Where I'm at now.

Yesterday I proved the TCM plug at the TCM and also checked power at the TCM wires when energized. Here is what I found.

Ohms:

Pin 1&2 (Input speed sensor Ground & signal -704 Ohms SHOULD BE 620 Oms

Pin 6&7 (CCD BUS -&+) 60.50hms S HOULD BE 60 Ohms

Voltage checks:

Cav 6 2.39Vdc (CCD BUS -) SHOULD BE 2.51

Cav 7 2.42 Vdc (CCD BUS +) SHOLD BE 2.49

TCM ENERGIZED:

Pins 25 & 26 Batt Voltage when it should be there

PIN 12 (SOLENOID A) .012Vdc WHEN KEY ON AND IN D. [It should be energized to call for 1st gear.]

The only solenoid energized throughout all gear selections is solenoid B

Cav 18 (R) energized when gear selected meaning the signal is being received by the TCM

Cav 22 (D) energized when gear selected meaning the signal is being received by the TCM

IN CONCLUSION

It looks like I may have a bad speed sensor (ohms and voltage are a little off)

Possibly a bad TCM? because it's receiving the signals, but it's not turning around and energizing the components it should be.

Ca
n anyone deduce something else going on here?

 

[lawsoncl]

The input speed sensor won't cause your issue, and I've never seen one fail. P0751 points to a solenoid A issue. Did you check the resistance across the solenoids (11-15 ohms)? Either the solenoid or the wiring is shorted to ground or the driver in the TCM is blown, or both.

 

[Dead Civic]

The input speed sensor won't cause your issue, and I've never seen one fail. P0751 points to a solenoid A issue. Did you check the resistance across the solenoids (11-15 ohms)? Either the solenoid or the wiring is shorted to ground or the driver in the TCM is blown, or both.

Thanks, I replaced the speed sensor. No change there but at least it's with intolerance. I replaced the solenoids twice, when I check the resistance at the TCM plug they're testing good they're at the high end 15 ohms but still good.

Now I'm looking for a TCM to purchase somewhere. Fingers crossed..

 

[Dragonslayer]

Testing the solenoids for resistance is a first step when trying to determine whether if they’re good. But it’s not enough.

You need to perform an activation test on each solenoid.

After establishing that the Ohms have read good, test the solenoids using a 9V DC battery (the same battery type used in transistor radios, smoke alarms, etc.). You should hear a sharp “click” (not a soft weak click).

Do this activation test on each solenoid a number of times.

I’ve had solenoids that had tested OK for Ohms - but did nothing when 9V DC was applied to them. I’ve also had solenoids that clicked OK once or twice, but then pooped-out dead right in my hands afterwards. This why I test each one multiple times.

I’ve found that the Denso (OEM) solenoids are consistently the best at passing this test. In my experience, the cheaper aftermarket solenoids have been a crapshoot, and I’ve had to return a few that were either DOA, or had behaved inconsistently.

 

[Dead Civic]

I did the activation also, hit them multiple times they worked well. Hoever I did go through ordering 3 sets because the TC solenoid would only have one click, but the all behave the same. So i thought that was normal. Do you know if it's supposed to have 2 clicks like the shift solenoids? Maybe that the problem... and oddly all the three sets had a bad TC solenoid...

 

[Dragonslayer]

All of the solenoids, including the TC solenoid, should click smartly each and every time voltage is applied to them. I’d say that the TC solenoids that you’ve got there are marginal.