57LSUK

Hi, wonder if any one can advise or steer me to link if previously covered?
I have a new build 57 Chevy with a LS1 and 4l60e from complete low mileage donor car.
ECU was set up by Arizona TPI and it has a painless loom. Issue is will not change up with out backing right off gas.
I have now had it scanned and fault code is PO752 and it noted 1-2 & 2-3 shift solenoids off.

I am a ex-body man not mechanic or computer wizard so in as simple terms as possible what should I do next?

Thanks in advance

mrvedit

The 4 gears are selected by two shift solenoids. While shift solenoids certainly can and do go bad, I would first check for a wiring/harness problem.
What year is the PCM?
If you are confident the wiring/harness/PCM are OK, then the you could change the shift solenoids. You only have to drop the pan and filter. They cost under $15 each.

57LSUK

Hi mrvedit

Nope, I'm not confident the fault isn't electrical have checked all the connections and fuses and unable to see anything obvious.
PCM is from donor vehicle and remapped in the states.
hoping someone can give me guidance before replacing solenoids.

Thanks Paul.

mrvedit

Where are you located? Sounds like perhaps overseas? A trans shop can quickly test things with a scanner. Or a tuner like HP Tuners.

If you are willing to perform an ohm-meter/continuity test from the PCM to the trans, I can create a wiring list for you, but need to know the year of the PCM. '98 and others are completely different. IIRC I created a list and helped someone recently with a similar problem with a '99 or later PCM.

57LSUK

Thanks very much for the offer, I'm over in the UK. Engine and trans including PCM is from a 2002 TransAm.

mrvedit

See my post #4 in this thread:

https://ls1tech.com/forums/automatic...lems-help.html

Pins #47 and #48 on the Red connector control the solenoids.
Here is the schematic of the internals of the 4L60E:

http://www.msgpio.com/manuals/mshift/wiring.html

So basically, each solenoid should always have +12V on one side (check the fuses!) and pins #47 and #48 then ground the solenoid to activate it.

If you drop the trans pan, you can do an ohm-meter continuity check from each solenoid to the PCM. You can stick a sewing needle into the PCM pins to make contact, then an alligator clip to the needle.

Is this what you are looking for?? If not let me know more specifically.

57LSUK

That is superb mrvedit!

Thanks for taking the time to post this information up.

Will let you know how I get on.

Regards Paul.

57LSUK

Hi chaps

Bit of an update for you to try and puzzle out if you can?

Solenoids confirmed all working ok. When car is on the ramp with wheels in the air it changes up and down 1, 2, 3, and 4 perfectly, however as soon as it's on all four wheels and driving along it wont change into second without backing right off the gas.

Any ideas? as per usual much appreciated!!!

mrvedit

Well, that sure is an unusual problem. If your trans shifts up and down with the wheels in the air, then it may very well be working properly.
The main difference between having the car in the air and on the road is engine load. The shift points depend very heavily on engine load; under heavy load the shifts occur much later. (And the details of determined by the tune.)
As I understand your post, it will shift when you let off the gas, i.e. reduce engine load.
Your PCM may be detecting more engine load than there really is. Engine load is determined by the TPS, MAP and MAF. Therefore, I suspect one of those sensors is sending the wrong signal. You can start by disconnecting the MAF. It should make little difference. (If it makes a big difference, the MAF or the MAF tuning is bad.)
If convenient, test the voltage on the TPS with the throttle closed; it should be between .15 and .45 volts; a much higher number might fool the PCM into thinking you are giving a lot of throttle.
Also check the amount of vacuum and make sure the MAP is hooked up and seeing that vacuum. A disconnected/clogged MAP might fool the computer into thinking you are at WOT.
A good scan tool (like HP Tuners) will tell you the TPS voltage, MAP value and much more without even opening the hood.

57LSUK

Hi mrvedit

As per my pm to you, pretty much exhausted the electrical checks begining to look like second gear band, will let you know when it's stripped.

Thanks for all the top quality advise.

Paul.