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U1255 code in many Modules

1527 Views 17 Replies 4 Participants Last post by  basscatt
1998 Seville STS, 4.6 engine, 80k miles

I was passing a truck under heavy throttle and the engine died like I turned the key off.
Mountain road on a curve with no power steering and no power brakes...very hairy!

The DTC code U1255 "lost communications" shows on all of the following... DDM , DIM, IPC, RFA, RIM, VTD, MSM. The PCM had no codes. At the same time "service stability system" showed on dash.
The "lost communications" possible causes listed are...
-Loose control module connectors
-Faulty Control Module
-Control modules poor electrical connection
-Control Modules harness open or shorted

The engine will not start (no spark), and there is an electric humming from the back of engine (without key on) that is draining the battery.

Where do I start to solve this? Any help would be greatly appreciated!!
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Fuel injection pressure is supplied by the pump inside the assembly inside the fuel tank.
That is the Fuel Pressure Regulator, on the fuel (injector) rail, fed by the high pressure fuel pump in the bottom of the fuel tank.
The vacuum line sends engine load to the FPR which then adjusts fuel pressure/flow to the injectors by altering the fuel bypass to tank rate of flow. It is not a pump, but may hum due to pump pulsation - the thing works with 41 - 50 psi of high flow fuel.

EDIT: The fuel pump runs for a second at KEY: ON to prime the system. It then stays off until the key is turned to START - then it runs during cranking. As the engine catches and comes up to idle speed the pump latches ON and runs the entire time the engine is running.

I strongly recommend that you subscribe the car to - the online GM/Cadillac service manuals - so you have some idea of what you're looking at and of what we're informing you.
PLEASE get the service manuals so you know what you're looking at.

There is no power - no power - to the Fuel Pressure Regulator. It is a control device for fuel pressure created by the fuel pump in the bottom of the fuel tank.

Here's your fuel pump assembly .............

Automotive fuel system Auto part Fuel pump
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