Hello AZ, first post, despite spending the majority of my free time over the last couple of months on here researching transmission issues. A million transmission threads on here, but can't find one like mine.

So here we go. 05 base, bought it with a bad trans. PO also bought it with a bad trans too. He did an AV6 swap with an older, 03ish, trans and failed. Could drive it, but it was slipping bad. He got frustrated and sold the car to me. As I was testing and diagnosing the vehicle, it eventually lost drive altogether on a test drive. So I bought another trans. Also an AV6, this one from an 07, advertised to have only 70k-ish miles. I got it in, passed visual inspection and fluud inspection, so I installed it. 3rd time appeared to be the charm, as the 3rd trans in this car in 2 months was driving around just fine, perfect shifts. I parked it for a few days until I had more free time to tighten up some loose ends. Well, when I came back the following weekend, it was now shifting into drive harshly, throwing a code for p0752 shift solenoid A stuck open, and would not shift out of 2nd into 3rd. 1 to 2 shift is still perfectly smooth, but it wont shift again, 2nd gear is max.

So I drained the fluid again. It was pretty gray, considering most of the fluid was swapped out during the trans install. And there was a layer on metal sludge on the magnet that would probably not concern you for 30k old fluid, but considering this fluid was a week old with maybe 5 miles, it was noteworthy. I removed the shift solenoid A from the old trans, cleaned and tested it, and swapped it with the current shift solenoid A. No change. So I removed all solenoids, cleaned and tested them, and reinstalled them. Also took apart the gear position range sensor apart and sanded the contacts clean, based off just a hunch since it was really the only common denominator between all 3 failed transmissions. And with another 5 miles or so of test driving, I did another drain and refill. Magnet was clean and fluid was redder, but still grayer than you'd expect. No metal material in fluid when strained through a rag.

Ok, so I am running out of ideas. Either this car is haunted and is just murdering trannies left and right, or I am overlooking something. The first replacement tranny appeared to be bad on install, this newer one was not. Also not sure that it is now, the gray fluid may just be old fluid that was stuck in the TC getting flushed out and mixed with the new. The 1-2 shift is still perfect and it drove perfect on its first test drive... Only ideas I have left are replacing the pressure switches, replacing the gear position range sensor, and replacing the APP sensor. But those all seem long shots given the current symptoms and I am hesitant to throw any more money at it. So any suggestions before I take a loss and pawn it off on someone else like the previous guy just did?

 

Since you removed & replaced the tranny, you should verify all the connectors are plugged in and no bent pins. Check the harness has not been damaged and that the transmission's ground cable is good.

I do have some questions:

1. Can you shift manually?
2. Can you shift into reverse after doing 1-2 shift?
3. Does the code come back immediately after clearing?

Once you have checked and if no problems found, continue with some tests.

Below is the shift control table, which shows which solenoids are on and off during shifts. The service manual does not say if ON is OPEN or CLOSE. Based on your symptoms and how the manual explains operation, I am going to assume ON is OPEN.

The transmission is controlled by the PCM through Connector C. The shift solenoid valve A is controlled on Connector C pin #1. Keep in mind the solenoids grounded to the transmission housing at G151.

Do these checks to confirm that the PCM is correctly commanding the solenoid on/off:

1. Check there is 0V at solenoid valve A while in Reverse and Neutral
2. Check there is Battery voltage at solenoid valve A when it shifts 1st and 2nd
3. Check it drops back down to 0V when it tries to shift to 3rd

Do these checks to confirm no excessive drop on the solenoid:

1. Measure voltage drop from BLU/YEL to battery positive when commanded ON. <0.3V
2. Measure voltage drop on BLK to battery negative when commanded ON. <0.3V
3. If you have amp probe, measure current on the BLU/YEL when commanded ON. It should be ~1A
   1. This is why load testing wires is very important. You can also use a bulb that draws ~1A to load test both positive and grounds to confirm they can actually deliver the power needed to the solenoids.

IF everything checks out, then retest the solenoids like in the video I posted below.

Hopefully this helps.

 

El Cheapo thanks for the super helpful reply!
​
#1. No I cannot shift manually. If I slide over to manual mode, the green dot on the dash moves over to M, but no numbers pop up in the box and the vehicle shifts (or doesn't shift) all on its on.
#2. Yes, I can shift into reverse after a 1-2 shift. IIRC it does get clunky though, will confirm.
#3. The code does not come back immediately. As I remember it, it will stay away for the first key cycle regardless of drive time or missed 3rd gear shifts, but pops up at the first 3rd gear attempt of the second key cycle.

I did find the shift command table. It makes sense that the code for shift solenoid stuck on pops up right as the 3rd gear shift should happen, as that is when that solenoid should make its first actuation. Also makes sense that shifts into D from P or N are harsh. Doesn't make sense that shifts into R are not harsh though?


I have done a resistance test and direct voltage test on both solenoids that have been used in that A position, those tests showed good. I will follow up with the more thorough test from the video as well as the the voltage check at PCM connector C later this week after the holiday. Thanks again for your assistance so far!

 

Double check the transmission ground strap at G151 and the wiring harness for rubbing.

What do you mean by direct voltage test?

Resistance checks are not the most useful tests because even a single strand of wire can show continuity. Voltage drop is preferred, and load testing is even better because it proves that the wire can provide the required power to the solenoids. You can load the wire by using a bulb.

The problem with testing solenoids by just applying voltage and hearing click is that it does not prove it will work under pressure. I have tested solenoids that passed resistance checks and clicked when I applied voltage, but they would not work under load.

Also, It would be easier to check if the PCM command gets to the solenoid if you have a bi-directional scanner.

 

By direct voltage, I was referring to the same test you did, directly applying voltage and checking for the "click". I understand that is not an ideal test, I will further test as best as possible with a multimeter. I do not have a bi directional scanner unfortunately.

Also, could you describe the location of the G151 ground? I recall 3 grounds, one that goes to the thermostat housing, one over by the tranny filter, and a lower one in the vicinity of the gear range selector and pressure switch.

 

I haven't had the assistance or equipment to do your suggested diagnosing yet, but I did do some testing just now and found a couple of interesting things.

1. With a test light, but the shifter in any position, no voltage is ever sent to solenoid A.
2. If you attempt to drive the vehicle without solenoid A plugged in, it defaults to a higher gear, I believe the missing 3rd gear! Although hard to tell, it could also be 4th or 5th.
3. With solenoid A unplugged, the hard shift into D disappears, but is now present shifting into R. Opposite is true with solenoid A plugged in.
4. After a ECU reset using the key on, key off, key on, hold accelerator for 30 secs method, key off method, the car will shift into 3rd ONE time.

I still plan to do the suggested diagnosing, but at this point I feel confident that the ECU is blocking 3rd shifts for some reason. Now that I can access 3rd gear, I do not observe any slipping or anything to suggest 3rd gear is failing in anyway. I can't understand why the PCM would be blocking it? Possibly a failing PCM?

 

Or another possibility, is this limp mode?? My understanding is limp mode limits you to 1-2 gear, and under 3k RPMs with a bunch of warning lights. I can rev past 3k, but the gears and dash lights would indicate limp mode.

 

Did you do it while driving?

The service manual is not very clear if the car has to be in motion for battery voltage to be applied to Solenoid A when in D.

Backprobe the Solenoid A BLU/YEL wire and keep an eye on the voltage while you drive.

If there is no voltage at the solenoid then verify the wire is not grounded.

You're going to have to backprobe Connector C pin#1 at the PCM to see if voltage is there. If no voltage at the PCM, then you'll need to do other troubleshooting.

 

Ok, interesting update. I backprobed pin 1 connector C. There IS voltage. At 3rd gear shift, voltage remains constant. I mentioned it trying to shift into 3rd with a PCM reset, and I can confirm that with the voltage test. After a PCM reset, voltage will drop to 0 momentarily and then return to 12.8v-ish. I thought it was shifting into 3rd, but looking at the voltage it appears to attempt to shift, rejects it and downshifts back to 2nd.

 

After further test driving, I noticed I can use manual mode right after a PCM reset aswell. Indicator on dash confirms what voltage test is saying. Car will shift into 3rd, bounce back into 2nd. According to the indicator, it will actually bounce between 2 and 3 a couple of times. And then of course once the PCM decides 3rd gear isn't working, indicator settles on 2, then turns off and blinking green dot return a few seconds later.

 

According to the shift solenoid control table, there should be 0V at 3rd.

• 1st = battery voltage
• 2nd = battery voltage
• 3rd = 0V
• 4th = 0V
• 5th = battery voltage
• P, R, N = 0

It seems to me that the PCM is commanding Solenoid A off by dropping the voltage to 0V at the 2-3 shift, but it somehow confirms it's not shifting so it goes back to 2nd and continues to apply the 12V.

• Have you also backprobed at the solenoid to compare it to the signal at the PCM?
• This is a brand new Solenoid A?
• Have you checked G151 is good?

 

It is not a new solenoid, but I have tried 3 different used ones. The original solenoid A, the solenoid A from the old transmission, and also swapped with the other black connector solenoid on top of the transmission, believe that is solenoid B and the problem did not move or change.

I don't know how I can backprobe the solenoid for the 2-3 shift. I suppose I could have someone step on the brake in drive and I can get a reading for 1st gear. I imagine if there is a reading there, we can assume the readings at all points would be the same as at connector C.

I did check G151. It was hooked up on a bracket close to the pressure switch, looked like it had never been loosen, no corrosion ot anything either. I did remove it and bolt it directly to the transmission case at a nearby bolt, but that made no difference aswell... I also checked the grounds on the ATF filter housing and thermostat housing, and they both appeared to be clean and secure aswell. If there are any other grounds, I am unaware of their location.

I did inspect the wiring harness and all connectors to the best of my ability. I dont see anything loose or damaged.

What is the likelihood the 3rd gear pressure switch is faulty and is the cause? Would that create this issue? And if so, where is it located on an 07 AV6?

 

It looks like Solenoid A and B are the same part. You'll need to confirm.

Looking at the shift control, Solenoid B is ON for 1-2-3 gears so it would not throw a trouble code if it was bad for your case since you can't get past 2nd.

It would be bad luck if they were all bad though.

Backprobe the connector like in the picture. Use alligator clips to connect to your meter. Make sure to use some tape to avoid shorting it to ground. Route the leads to inside and keep an eye on the meter as you drive.

This is where a bi-directional scanner helps a lot. You could just command it on and off with a scanner without having to drive the car. You would also be able to connect a light bulb and test for wire integrity.

The BLK ground wire can be tested by using a light bulb since it's always connected to ground.





I was just thinking about pressure testing. At that point, it could be a blocked oil passage way.

However, I am not experienced enough to guide anyone on it. You might need to take it to a transmission shop, but be ready for them to say you need a rebuild.

 

Just a stray thought, have you checked to see if you're losing coolant? I'm thinking there is a remote possibility the gray ATF might be a coolant leak at the intercooler in the radiator. Yeah, I know, pretty thin, but just a thought.

 

Good point.

I just assumed it was old ATF still in the tranny.

OP can pressure test the cooling system to see if it's leaking. At least it will rule it out.

 

My car is not equipped with a transmission cooler, just the warmer on top. It is possible that could be leaking though, worth a check.

 

I'm not sure why folks call it a "warmer", your car has no facility to warm the ATF except for driving the car.

 

Im having same problem I think I've drained fluid and coolant mix in trans and radiator I have a BDGA trainsmission where the coolant and trans fluid.goes in to on top of trany, I was trying to figure out how to get it out of torch converter. Before I found out trouble my code reader said pressured soliniod trouble. Just a thought.

 

Is there a way to test for coolant in the ATF? I dont have a cooling system pressure tester.

 

Also, tried replacing the pressure switches to no avail.

 

If there is ATF in the coolant, it will float to the top of the coolant. Open the Radiator Cap, it should be obvious.

 

There is no ATF in the coolant, coolant looks fine, albiet low. Im not sure if there is coolant in the ATF though.

 

Three ways of checking if there is coolant in the ATF:

• Used Oil Analysis (costs money and takes a couple of weeks but is definitive).
• Seeing a milky emulsion on the transmission dipstick.
• Seeing the level of the ATF rise over time.

 

I think you can "rent" a pressure tester at AutoZone.

Have you replaced any of them with new parts?

​​​​​​It sounds like you don't have a coolant problem. But who knows.

I think it might be time to take it to a professional.