P2A99 belongs to installations with at least three selectable vessels or supplies and reports an open or otherwise broken control circuit at select valve C. Published designs mostly show two vessels, such as Westport's LNG arrangement with one pump and a valve choosing the tank, or Cespira's pair of compressed-gas supplies; a third valve extends the same principle. With valve C unpowered, its vessel can neither be brought on line nor, depending on the rest position, taken off line, so the selection sequence breaks at that point. Take care not to confuse it with P2A26, the shutoff solenoid on tank C, or with the hydraulic pump select valve. No manufacturer documents P2A99. Check the plug, the lead and the coil of valve C.
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
- Malfunction lamp on
- Third vessel stays full or is never isolated
- Total range reduced
Most likely causes
- Disconnected plug or broken lead at select valve C
- Coil of valve C burnt out
- Module output for valve C failed
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It can trigger limp mode.
- It affects emissions.
What each character of P2A99 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- A: Hybrid or air and fuel
- 99: Specific fault in that system
Frequently asked questions
Can I keep driving with code P2A99?
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 P2A99?
The most common causes are: disconnected plug or broken lead at select valve C; coil of valve C burnt out; module output for valve C failed.
Related codes
- P2A9AAlternative Fuel Tank Select Valve C Control Circuit Performance
- P2A9BAlternative Fuel Tank Select Valve C Control Circuit Low
- P2A9CAlternative Fuel Tank Select Valve C Control Circuit High
- P2A91Alternative Fuel Tank Select Valve A Control Circuit/Open
- P2A95Alternative Fuel Tank Select Valve B Control Circuit/Open
- P2A26Alternative Fuel Tank Shutoff Valve C Control Circuit/Open
Sources
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.