Powertrain, generic · Fuel and air metering

P01C9 Fuel Rail/System Pressure - Too High Bank 2

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Some V engines have a separate high-pressure fuel circuit per bank, each with its own pump or rail – for example Audi's 4.0 TFSI V8 with a second high-pressure pump for bank 2. These codes are the bank 2 counterparts of the system pressure codes for bank 1. P01C9 is the bank 2 counterpart of P0088: the actual pressure is above target. Audi documents it on 2013–2014 A8/S8 and S6/S7 4.0 TFSI models together with P0088: at low supply voltage the duty cycle of the volume control valve was no longer sufficient, the valve stayed shut and the pump delivered full flow – audible as noise from pump 2, sometimes with slightly reduced power. The fix was a software update. Not every two-rail engine uses them: GM's LT6 reports bank 2 pressure problems under other codes.

Likely causes

Volume control valve not controlled properly (e.g. at low supply voltage), software
Volume control valve sticking
Bank 2 rail pressure sensor reading too high
Pressure relief path blocked

Symptoms

  • Check engine light on (possibly intermittent)
  • Noise from the bank 2 high-pressure pump
  • Slightly reduced power possible

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–1,200
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

high pressure fuel pump bank2fuel volume control valvefuel rail bank2

Related codes

P0088P01C8P01CAP01BF

References: law.cornell.edu, static.nhtsa.gov, static.nhtsa.gov.