Fuel tank pressure sensor fault with 5v 1 reference circuit low

Derrick Diagnostician United Arab Emirates Posted   Latest  
Unsolved
Electrical
2009 Cadillac CTS V 6.2L (P LSA) 6-spd (6L90)
Engine Light

Hello, professionals,I have a challenge on this model​.​vehicle misfires with engine light on​.​we have renewed EVAP canister and new fuel tank pressure sensor but faults have remained current​.​there are now visual signs for short in wiring harness and the 3pin wires from FTP sensor connector to the engine control unit have continuity and no damages.

I test for 5volts not present and instead have the all the 3 wires show ground present.

My all data is damaged and have no proper wiring diagram for this ECU to check out the what could be triggering a short in the 5v1 reference circuit.

Any assistance please 🙏..thank you.

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Kerry Mobile Technician
Ohio
Kerry
 

Hopefully you can blow these up to read them!

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Derrick Diagnostician
United Arab Emirates
Derrick
 

Thank you kerry

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Derrick Diagnostician
United Arab Emirates
Derrick
 

Greetings to you kerry,I am very much impressed 👍 for you support​.​am sure now will be able to identify the short in the circuit. Please advise or how can we get a copy of identifix softwares to enable our shop meet timely deadlines and ease with our work mostly for workshop information systems. Thank you. … Derrick.

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Gary Diagnostician
New Jersey
Gary
 

I have seen the air conditioning pressure switch, or the a/c harness short out multiple times taking the 5 volt reference circuit down. Unplug and recheck ftp circuit.

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Derrick Diagnostician
United Arab Emirates
Derrick
 

Many thanks Gary.

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Timothy Owner/Technician
Wisconsin
Timothy
 

That VREF feeds the ACP, APP sensor 2, Baro sensor, CMP sensor, EOP sensor, FTP sensor, and finally, the SC air inlet pressure sensor. Any one of which could pull down the VREF. Since you've posted no codes, I can't really go beyond what you got already. If you've no SI, it would be difficult to repair. You can always try disconnecting sensors one at a time, and see if the VREF comes back…

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Derrick Diagnostician
United Arab Emirates
Derrick
 

Thank you Timothy…I have got it.

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