P01C9: Fuel Rail/System Pressure - Too High Bank 2

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.

Bank 2 is the side without cylinder 1, so it only exists on V or boxer engines.

Symptoms

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

Most 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

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the pump's fuse, relay, and connector
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Replace the filter if it is due for maintenance
4. Compare commanded and actual pressure in live data
5. Measure the pressure with a suitable gauge
6. Check the sensor and regulator before replacing the pump

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P01C9 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 1: Air and fuel
• C9: Specific fault in that system

Frequently asked questions

Can I keep driving with code P01C9?

Avoid long trips and hard acceleration. If you smell fuel or the car stalls, do not continue.

What causes code P01C9?

The most common causes are: 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.

Related codes

• P0088Fuel Rail/System Pressure - Too High
• P01C8Fuel Rail/System Pressure - Too Low Bank 2
• P01CAFuel Rail Pressure Too Low - Engine Cranking Bank 2
• P01BFFuel Rail Pressure Sensor Circuit Range/Performance Bank 2

Sources

• law.cornell.edu: 13 CCR 1968.2
• static.nhtsa.gov: MC 10122182 9999
• static.nhtsa.gov: SB 10054273 9452

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.