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Ask Juan Crespo Your Own Question
Juan Crespo
Juan Crespo, Tech Trainer
Category: GMC
Satisfied Customers: 1526
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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P0975 ***** *****
, Its in limp mode second only and

Customer Question

p0975 ***** *****
JA: Thanks. Can you give me any more details about your issue?
Customer: Its in limp mode second only and reverse
JA: OK got it. Last thing — GM Mechanics generally expect a deposit of about $32 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 1 year ago.
Category: GMC
Customer: replied 1 year ago.
Ok the customers truck was working normal till this morning came to stop light started out in second has not shifted up or down even in manual low
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Tims Auto Repair replied 1 year ago.

Hi, My name is ***** ***** for the delay.

I will do my best to assist you

what is the year?

what engine and transmission do you have?

is the p0975 the only code you get?


Customer: replied 1 year ago.
09 gmc 5500 6.6L allison p0975 is the only code on the transmission side glow plug code on engine side
we have ohm tested all the solenoids in the pan
Customer: replied 1 year ago.
Sorry it has been crazy here today so i will keep checking the CPU for updates from you
Expert:  Tims Auto Repair replied 1 year ago.

ok..please stand by

one of our heavy equipment guys will be right with you


Customer: replied 1 year ago.
We are here!!
Customer: replied 1 year ago.
We are here waiting
Expert:  Juan Crespo replied 1 year ago.

Hi there. Sorry that you had to wait for one of us to get free.

Code P0975 is set when the transmision module (TCM) detects an open in the shift solenoid #2 circuit (SS2). The most common seen cause for the code and the symptoms you describe is a bad connection at the 21-pin connector on the valve body - sometimes the fix is as simple as unplugging the connector, cleaning both halves with WD40 and plugging it back together. Second most seen is a an open SS2 solenoid winding - which means taking down the valve body and replacing SS2. Third is a bad TCM - the replacement would have to be programmed to the vehicle.

Please let me know if you have any other questions.

Best Regards.

Customer: replied 1 year ago.
Can you get me a pin out diagram of the case connector and the pcm?
Customer: replied 1 year ago.
We need a pin out diagram of the case connector and the TCM Would you please call Brian @(###) ###-####ASAP please!
Expert:  Juan Crespo replied 1 year ago.

Hi Brian.

Sorry about that phone call, but besides site rules not allowing experts to call customers without the customer first making a request to that effect, I retired to the Dominican Republic a while back; a phone call from here would cost me way more than what you would pay Just Answer to have me call you. If you want an expert to call you, just fill the appropriate request. Then I'll opt out to give other experts the chance to accept and call you.

Just out of curiosity, what would you do with a pinout diagram when only the SS2 circuit is affected? Wouldn't it be better to focus on the issue that's affecting the tranny and causing the code to set?

Customer: replied 1 year ago.
Its not in the trans! its in the wiring feeding the trans
Expert:  Juan Crespo replied 1 year ago.

OK. Here are the pinouts; TCM connector, 21-pin connector and SS2 connector.

Since P0975 only sets when there's an open in the solenoid control circuit, my advice is to focus on that one circuit.

Please let me know if you have any other questions concerning this issue.

Best Regards.

Expert:  Juan Crespo replied 1 year ago.

A couple of images might not have gone through on my previous post. Here they are just in case.

Best Regards.