kevaughan

I am getting a p0758 code which is shift solenoid b electrical. I have changed all 4 solenoids, internal wiring harness, ignition switch, pcm and checked resistance between pcm and trans. Could the pressure manifold switch cause this problem.

mrvedit

Some people have reported P0758 when running a high stall converter. Are you? Correction: A high stall might cause a P0756 (see below).
They then use a tuner to disable this code.
I am not aware of a bad pressure switch manifold causing this code, but it can cause very strange problems that make no sense.

kevaughan

no high stall

mrvedit

Researching this further, I see that it is P0756 (Solenoid B Performance) that is sometimes caused by a high stall converter.
P0758 (Solenoid B Electrical) seems to an electrical continuity problem.
Since you already replaced the solenoid, internal harness and even PCM, you have covered the most obvious bases.

I would drop the pan, turn on the ignition and check the voltage on the "ground" side of Solenoid B. If there is a bad connection in the path to the PCM, the voltage might be higher than the 0.5 volts (or less) that I would expect. Obviously the other side of the solenoid should be at +12 volts. Kinda grasping for straws here, but beyond that I am at a loss. If the trans is shifting fine, you might just tune it out.

kevaughan

Ok I'll look at that, at this point I'm grasping myself. Thanks for the input.

kevaughan

Sorry it took so long to check this. Instead of dropping the pan again I checked voltage on the wire at pin 4 ( yellow/black ) it had 11.7 volts not .5 this is in park. Same in od.

mrvedit

Even in [P]ark, both solenoids should be on and the voltage on the Yellow/Black wire to Solenoid B should be about 0.5V or less.
Most diagrams show this as "Pin B" not pin 4:

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

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

Sounds like you are well on your way to figuring this out. Perhaps you can find that wire near the PCM and check voltage there. (I use a tiny sewing needle to piece the insulation and put a alligator clip on the needle.)

kevaughan

Where I checked was at the pcm red connector pin 4 which is b at the trans. With the ignition on and not running 12 volts no matter what gear it's in. With running 0.395 volts any gear.

kevaughan

Drove the truck while checking voltage at pcm 1-2 0.384-0.398 volts shifts into 3rd 13.96-14.02 volts. Manual shift back to 2nd back to basic no voltage manual shift to 3rd back to basic 14 volts.

mrvedit

So, you are saying that the solenoids are only ON when the engine is running. I did not know that, sorry for any confusion. I test solenoids with HP Tuner's scanner and I can hear them click on/off with the engine off.

So, you are saying that the trans shifts correctly and the voltages are correct. If you clear the code, does it come back immediately, the 1st time you shift through the gears, or at some random later time?

kevaughan

When I clear the code it will come back the 1st time it shifts though the gears.