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Ron, ASE Certified Technician
Category: Pontiac
Satisfied Customers: 34427
Experience:  34 years as a Tech
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Have a g6 and the speedometer is not reading correct speed

Customer Question

My name is ***** ***** a g6 and the speedometer is not reading correct speed trans is showing correct speed ecm shows 20 mph when going 60
JA: Thanks. Can you give me any more details about your issue?
Customer: The ipc shows speed incorrect the ecm also shows speed incorrect but the speed on the tcm shows correct
JA: OK got it. Last thing — Pontiac Mechanics generally expect a deposit of about $18 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: Pontiac
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:  Ron replied 1 year ago.

Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.


Can you tell me what year your G6 is and also, are you able to scan the computer system and see if there are any fault codes setting. Post back with complete information and I will try and help you get this resolved.

Customer: replied 1 year ago.
It is a 2007 gtp model there are no fault codes in any module I understand the ecm sends signal to bcm then to ipc but were does the ecm get this signal the transmission shift points are all correct and by data stream the output speed sensor reads correct speed in the tcm
Customer: replied 1 year ago.
I am a master A S E, L1 tech also with 34 years experience just looking for an answer or help where to go this one is stumping me
Expert:  Ron replied 1 year ago.

Bill the VSS signal is sent to the TCM and from there to the ECM, if your getting correct speed at the TCM then you are most likely dealing with a problem with either the ECM or the circuit from the TCM to the ECM. See the steps in the link below to check it. Copy and paste the link to your browser to open and view it.