These codes only apply to vehicles that run on a gaseous alternative fuel – compressed natural gas (CNG) or LPG – either as bi-fuel models alongside petrol (for example GM's 2015–2016 Impala Bi-Fuel or 2013–2016 Silverado/Sierra 2500HD) or as dedicated gas engines. CNG is stored at up to about 250 bar (3600 psi); a regulator reduces it to a few bar for the gas rail and injectors. The gas rail pressure sensor measures the regulated low pressure at the rail – on GM's Impala controlled by the engine module to 68–130 psi (about 4.7–9 bar) – so that injection time can be matched to the actual gas pressure and density. P01A6 means the signal voltage is above its upper limit – an open sensor ground or a signal wire shorted to 5 V or battery voltage. Typical reaction: gas operation is blocked and a bi-fuel vehicle switches to petrol. No manufacturer document naming exactly this code was found; GM's bulletins only state that faults are reported like on petrol models. The description rests on CARB, which treats such vehicles like petrol engines for model years 2004–2018, and on the documented system design.
High severity. Can I keep driving?If you smell gas, do not keep driving or start the engine: move away and call for assistance. With no smell, drive moderately to an authorized shop.
Symptoms
- Check engine light on
- Switch to petrol or gas operation not selectable
- Hesitation, loss of power or mixture faults in gas mode
- Dedicated gas engines: limp mode or starting problems
Most likely causes
- Sensor ground wire open
- Signal wire shorted to 5 V or battery voltage
- Gas rail pressure sensor faulty
- Control module faulty
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P01A6 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 1: Air and fuel
- A6: Specific fault in that system
Frequently asked questions
Can I keep driving with code P01A6?
If you smell gas, do not keep driving or start the engine: move away and call for assistance. With no smell, drive moderately to an authorized shop.
What causes code P01A6?
The most common causes are: sensor ground wire open; signal wire shorted to 5 V or battery voltage; gas rail pressure sensor faulty.
Related codes
- P01A3Alternative Fuel Rail Pressure Sensor Circuit
- P01A4Alternative Fuel Rail Pressure Sensor Performance
- P01A5Alternative Fuel Rail Pressure Sensor Circuit Low
- P01A7Alternative Fuel Rail Pressure Sensor Circuit Intermittent/Erratic
- P01A8Alternative Fuel Rail/System Pressure - Too Low
- P01A9Alternative Fuel Rail/System Pressure - Too High
Sources
- law.cornell.edu: 13 CCR 1968.2
- static.nhtsa.gov: MC 10114282 9999
- static.nhtsa.gov: INRD PE08063 33504P
- patents.google.com: en
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.