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Dan
Dan, Technician
Category: Chevy
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Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Chevrolet Blazer my solenoid B PO756 keeps going out, I can

Resolved Question:

my solenoid B PO756 keeps going out, I can run manually but when solenoid is in stuck I can't use drive. Clear the code, turn it off and it sometimes will work. I have had it all over to transmission places. Replaced the solenoid twice and changed fluid three times. It always looks good. Why does it keep going out? 2002 chevy blazer LS two wheel drive
This has been a three year ordeal!
Submitted: 5 years ago.
Category: Chevy
Expert:  Dan replied 5 years ago.

Welcome to JustAnswer, my name is XXXXX XXXXX I'm here to help get your problem resolved. Ask follow up questions, thanks.

 

The powertrain control module controls the solenoid so I'd start by replacing pcm after verifying wiring between pcm and solenoid is good. You can get a used pcm from www.car-parts.com to save money. Let me know if you have questions, thanks.

Customer: replied 5 years ago.

I don't have any codes associated with replacing that. People have replaced this and ended up with the same problem

Expert:  Dan replied 5 years ago.

Otherwise valve body will need to be removed, dissasembled, and cleaned because this could be caused by a sticking vavle. Here is a TSB released by GM for the issue.

 

graphic

 

 

P0756 2-3 Shift Solenoid Valve Performance - No 2nd Or 3rd Gear - With Automatic Transmission

Possible CausesSetting Conditions
  • ATF is burnt or contaminated
  • Transmission has plugged or restricted fluid circuits
  • Shift solenoid valve seals are leaking or damaged
  • Transmission has failed
DTC P0122, P0123, P0502, P0503, P0740, P0742, P0753, P0758, P0785, P1810, P1860 and P2761 not set; engine speed over 450 rpm for 5 seconds, system voltage from 10-18.0v, not in Decel Fuel Cutoff, TP angle over 10, gear range is D4 with no change for 6 seconds, TFT signal from 68-266ºF, engine torque 50-400 lb ft., Output speed more than 150 rpm, then 1st gear commanded "on" for 2 seconds with the engine torque from 50-400 lb ft., the PCM detected the estimated gear ratio equaled 0.1-1.0 for one second, or with 2nd gear commanded "on" for 1 second with the engine torque from 50-400 lb ft., the PCM detected the estimated gear ratio equaled 0.9-1.2 for two seconds, either fault detected twice on one trip.

This code sets in 1 Trip(s).
This code will turn on the MIL (Malfunction Indicator Lamp)

Customer: replied 5 years ago.

I had the entire transmission cleaned out looked in holes replaced solenoid twice and the harness. The fluid was always clean and no blockage

Expert:  Dan replied 5 years ago.
A simple transmission flush isnt enough if one of the valves or passages in the valve body get cleaned out.......So valve body will need to be removed, taken apart, cleaned, and reinstalled. Let me know if you have questions, thanks.
Customer: replied 5 years ago.

I think the guy already did alot of this stuff I know he cleaned out #29 and all that surrounded that. I do know they are known to get sticky. Is there anything else I should be looking at?

Expert:  Dan replied 5 years ago.
Not really....If valve moved freely and nothing is clogged then problem is either electrical "pcm" or transmission mechanical. Let me know if you have questions, thanks.
Customer: replied 5 years ago.

If its an electrical problem it would come up with a different code and that is not the case

Expert:  Dan replied 5 years ago.
If valve body is good then the only other possible option is the transmission itself if its not electrical.
Customer: replied 5 years ago.

I did forget this, I kind of know when it will happen cause my lights on the dash including the radio and clock with click on and off. And if the stop sign is on a uphill slope it is more prone to do it then.

Expert:  Dan replied 5 years ago.
You could have a electrical problem, you would need to monitor voltage going to transmission for solenoids to see if voltage drop happens when this happens. If so then you could be looking at a ignition switch problem.
Customer: replied 5 years ago.

How can I monitor it if it happens whenever it wants? It can go for months with no problems and then out of the blue it'll go out. Always when I have to stop in traffic.

Expert:  Dan replied 5 years ago.

Your going to have to connect a testlead to transmission solenoid and run it into cab then keep voltmeter on you...So when problem happens you can monitor voltage. Let me know if you have questions, thanks.

Customer: replied 5 years ago.

the solenoid is in the transmission

Expert:  Dan replied 5 years ago.
You can connect to the wire where it goes into the transmission, it is a pink wire. Let me know if you have questions, thanks.
Customer: replied 5 years ago.

and I can drive it around like that?

Expert:  Dan replied 5 years ago.
Yes, just dont short wire to ground or fuse will blow. You could just have a wire going to cab with a cap on it. Then take cap off to test when problem starts. Let me know if you have questions, thanks.
Customer: replied 5 years ago.

Thankyou very much Dan, I will try these things out. Thanks for your time.

Expert:  Dan replied 5 years ago.
No problem, let me know how it goes or if you run into questions...Thanks.
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