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Ron, ASE Certified Technician
Category: Cadillac
Satisfied Customers: 36077
Experience:  34 year as an ASE Tech
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Have p0089 on 2008 STS 3.6. Just hesitating a bit here and

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Have p0089 on 2008 STS 3.6. Just hesitating a bit here and there. Changed fuel filter. No change. Is this automatically fuel pump?
JA: Is the fuel filter an external one, or is it inside the tank?
Customer: External
JA: Are you fixing your STS yourself? What have you tried so far?
Customer: Just replaced filter. High mileage car. Sure dealer will run bill up so exploring options
JA: Anything else you want the mechanic to know before I connect you?
Customer: No

Hello. My name is ***** ***** I am happy to assist you today. Give me just a moment to review your post, and I'll be right back with the help you need.

The most common cause for the P0089 to set on your CTS is in most cases a failing high pressure fuel pump. Do you have access to a scan tool that can read the fuel pressure values while the problem is occurring?

Customer: replied 4 months ago.
Probably not an issue but car is STS not CTS. In 2008 STS, is high pressure pump accessible via rear seat or do you have to drop the tank? I can get to someone with scan tool tomorrow. Have 235,000 miles. Runs great but assessing whether worth replacing pump

Sorry the CTS was a typo on my part but the answer remains the same. You will want to check the Fuel Rail Pressure Sensor value on the scanner. The pressure should be approximately 3.5–5.5 MPa (508–798 PSI). Attempt to command the fuel pressure high using the scanner. The high pressure pump on your 3.6 is not in the tank, it mount to the engine . See the link below.

Customer: replied 4 months ago.
That makes sense!. Low pressure pump in tank just feeds high pressure on engine? Appreciate your help Ron. If I have questions tomorrow after scan, can I reach back out or do I have to initiate another conversation?

Yes the post remains open as long as you need me even after you rate the service simply post back if need be. Please take a moment to rate my service so I can get credit for my time, the question remains open for follow up even after doing so, all you need to do is return to this question if need be.

Thank you again.

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