P2A90 marks pump C of the alternative fuel system as delivering too little. A third pump may belong to a further tank or, in Caterpillar's design US10060421B2, be one of several pumping elements driven in sequence. Besides wear, cryogenic pumps have a typical weakness that Caterpillar's patent US9228574B2 describes: if the liquid at the inlet has warmed enough to form vapour, the pump cavitates and delivery stops, so centrifugal designs need a positive feed pressure. Short bursts of poor output after long parking, with warmer LNG in the tank, fit this picture; a permanent shortfall points to worn parts. The pump diagnosis in US20080302111A1 explains how a slow pressure rise reveals the loss. No manufacturer publishes P2A90; P2A87 to P2A8A cover pump C's stroke valve.
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
- Warning lamp on
- Weak pull or hesitation shortly after a long stop
- Gas pressure recovers slowly after heavy acceleration
Most likely causes
- Vapour at the inlet of pump C after warm soak, causing cavitation
- Worn seals or valves in pump C
- Clogged inlet strainer or filter ahead of pump C
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- It can trigger limp mode.
- It affects emissions.
What each character of P2A90 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- A: Hybrid or air and fuel
- 90: Specific fault in that system
Frequently asked questions
Can I keep driving with code P2A90?
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 P2A90?
The most common causes are: vapour at the inlet of pump C after warm soak, causing cavitation; worn seals or valves in pump C; clogged inlet strainer or filter ahead of pump C.
Related codes
- P2A8EAlternative Fuel Pump A Performance
- P2A8FAlternative Fuel Pump B Performance
- P2A87Alternative Fuel Pump C Compression Stroke Valve Control Circuit/Open
- P2A88Alternative Fuel Pump C Compression Stroke Valve Control Circuit Range/Performance
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.