I have a 2025 Ultima Rs that has the Lt4 swap into it. On first startup, the High side pump is showing maxxed out at 95,050psi, and has no throttle response. Last vehicle that has similar, but not the same issues ended up being can bus leads being inverted on the blue and black plug. But diagnosing that was above my grade. Included is the file and log.
Last edited by Flipper7; 05-10-2025 at 02:00 PM.
HPFP wiring I bet wrong harness to that connection..
What codes are you getting.
I have an Ultima RS as well
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96 TA Blown/Stroked, 4L80E/Fab 9
15 C7 A8 H/C 2.3 Blower/PI
14 Gen5 Viper
Ultima RS with C8 drivetrain
Originally Posted by Ben Charles
Codes
p0033 S/c bypass valve control circuit open
p0034 S/c bypass valve control circuit low
p0443 Evap control valve circuit
p0458 Evap control valve circuit low
p0481 Fan 2 Control circuit
p0651 Sensor Reference Voltage B Circuit open
p129d Fuel pump driver control mod Ign on
p16E5
p2227 Baro Pressure Sensor Perf
p2229 Baro Pressure sensor circuit high voltage
Yes, last vehicle that had the early and late fuel pressure sensor wiring incorrect was diagnosed from Mitch@ Swaptime via GHuggins. That vehicle had about 20+ codes due to the can leads being inverted.
Have you had any luck with figuring this out? I?m having very similar codes
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