These codes only apply to vehicles with a gaseous alternative fuel – compressed natural gas (CNG) or LPG – as bi-fuel models alongside petrol or as dedicated gas engines; on bi-fuel vehicles a fault usually blocks gas operation and the vehicle runs on petrol. Tank level sensor A only exists where there is a real sender – typically LPG tanks with a float whose position is transmitted magnetically through the tank wall (Roush propane systems: 0.1–4.9 V). With CNG the 'level' is a calculated value. The documented systems report level faults under the petrol fuel level codes (Roush propane P0460–P0463, GM CNG van P0463), so no manufacturer document using exactly this code was found. P01AF is the general circuit fault of this sender.
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
- Gas level display wrong, jumping or empty
- Range or refuelling information unreliable
Most likely causes
- Connector or wiring of the level sensor open, corroded or chafed
- Sensor faulty
- Gas module, CAN link or engine module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P01AF means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 1: Air and fuel
- AF: Specific fault in that system
Frequently asked questions
Can I keep driving with code P01AF?
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 P01AF?
The most common causes are: connector or wiring of the level sensor open, corroded or chafed; sensor faulty; gas module, CAN link or engine module.
Related codes
- P01B0Alternative Fuel Tank A Level Sensor Range/Performance
- P01B1Alternative Fuel Tank A Level Sensor Circuit Low
- P01B2Alternative Fuel Tank A Level Sensor Circuit High
- P01B3Alternative Fuel Tank A Level Sensor Circuit Intermittent/Erratic
- P0460Fuel Level Sensor A Circuit
Sources
- law.cornell.edu: 13 CCR 1968.2
- roushcleantech.com: Gen 4 Fuel Diagnostic Worksheet
- eur-lex.europa.eu: HTML
- static.nhtsa.gov: MC 10118628 9999
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.