P0756 2002 Sonoma

[sferguson]

Changed tranny fluid and filter on my wife's 02 Sonoma 4.3L 4x4 at 65,000 miles. As soon as I put it in drive 1st gear acted like it was slipping (rpms up but barely moving). Finally it would get going and everything shifted fine until it came to a complete stop and it would slip again. DTC code P0756 shift solenoid B was thrown. The odd thing is I can put shift selector in 1st gear and it drives fine. Where is the shift solenoid B located? Is there a procedure? I just changed the valve body in my 2001 Saturn Christmas Eve the day before this happened!! Thanks in advance

[minibike132]

HMMMM, maybe this can help...if you have a trans manual and can find the # 29 orifice. The important thing to note here is this code is caused by a mechanical not electronic malfunction. Most likely causes binding valve or debris. Odd that a fluid and filter change would cause this though. Did you flush or use any additives?

 

 

Subject:Info - Diagnostic Tips For Automatic Transmission DTC P0756, Second, Third, Fourth Gear Start #01-07-30-036F - (02/14/2006)

 

 

 

 

 

 

Models:2007 and Prior Passenger Cars and Light Duty Trucks

 

 

2003-2007 HUMMER H2

 

 

2006-2007 HUMMER H3

 

 

2005-2007 Saab 9-7X

 

 

with 4L60-E, 4L65-E or 4L70-E Automatic Transmission (RPOs M30, M32 or M70)

 

 

 

 

This bulletin is being revised to add the 2007 model year and 4L70-E transmission. Please discard Corporate Bulletin Number 01-07-30-036E (Section 07 - Transmission/Transaxle).

 

Some dealership technicians may have difficulty diagnosing DTC P0756, 2-3 Shift Valve Performance on 4L60-E, 4L65-E or 4L70-E automatic transmissions. As detailed in the Service Manual, when the PCM detects a 4-3-3-4 shift pattern, DTC P0756 will set. Some customers may also describe a condition of a second, third or forth gear start that may have the same causes but has not set this DTC yet. Below are some tips when diagnosing this DTC:

 

 

• This is a performance code. This means that a mechanical malfunction exists.

 

 

• This code is not set by electrical issues such as a damaged wiring harness or poor electrical connections. Electrical problems would cause a DTC P0758, P0787 or P0788 to set.

 

 

• The most likely cause is chips/debris plugging the filtered AFL oil at orifice #29 on the top of the spacer plate (48). This is a very small hole and is easily plugged by a small amount of debris. It is important to remove the spacer plate and inspect orifice #29 and the immediate area for the presence of chips/debris. Also, the transmission case passage directly above this orifice and the valve body passage directly below should be inspected and cleaned of any chips/debris.

 

 

• This code could be set if the 2-3 shift valve (368) were stuck or hung-up in its bore. Inspect the 2-3 shift valve (368) and the 2-3 shuttle valve (369) for free movement or damage and clean the valves, the bore and the valve body passages.

 

 

• This code could be set by a 2-3 shift solenoid (367b) if it were cracked, broken or leaking. Refer to Shift Solenoid Leak Test in the appropriate Service Manual for the leak test procedure. Based on parts return findings, a damaged or leaking shift solenoid is the least likely cause of this condition. Simply replacing a shift solenoid will not correct this condition unless the solenoid has been found to be cracked, broken or leaking.

 

It is important to also refer to the appropriate Service Manual for further possible causes of this condition.

 

 

 

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

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© Copyright General Motors Corporation. All Rights Reserved.

 

 

[sferguson]

Thanks sparkstech for the TSB. No additives jut Castrol tranny fluid. Pan did have alot of junk in bottom.. When doing the fluid change, I didn't move the crossmember out of the way so when putting the pan on I'm assuming I hit the solenoids while trying to muscle it in there. It is a very tight fit. Now that I have the pan off and looking at how the pan goes on; I see clearly that I could have wacked them pretty good. It does mention in the TSB about free movement of the shift solenoids could cause the code and the solenoid in question does wobble alot more than the one beside it. I have removed it and inspected it for cracks and it doesn't seem broken but you never know. I found a new set of both shift solenoids on ebay cheaper than I could get one solenoid from the local parts houses, so I'm going to replace both for $30.00 and find a way to move the cross member out of the way when installing the pan so I don't repeat the process. I would like to get a diagram of the tranny for reference if anybody has a link. Thanks again.

[sferguson]

Changed both solenoids and moved the cross member out of the way to put pan on and she drives like new. If a shop charges less than 50 bucks for this service then they can do it next time. It is not worth the hassle. If you have side steps on the vehicle, you will have to remove the passenger side to get at the bolts for the cross member.