Reductant Injection Air Pump Control Circuit High

Possible causes

• CommonReductant tank empty or very low
• CommonCrystallised deposits around the injector or in the lines
• CommonCorroded or water-ingressed connector - much of this system is under the vehicle
• CommonWiring damage underneath
• CommonContaminated, diluted or out-of-date reductant fluid
• PossibleFrozen reductant in cold weather, with a failed tank heater
• PossibleFailed reductant pump or supply module

What you might notice

• Warning that the vehicle will not restart after a certain distance
• Reduced power or a speed limit imposed
• Reductant or emissions system warning message
• Failed emissions test
• White crystalline deposits around the injector or pipework

What to check, in order

1. Check the reductant tank level first. An empty tank is the most common cause by a wide margin, and on many vehicles running out triggers a legally mandated countdown that ends with the engine refusing to restart.
2. Do not ignore a restart countdown. Once it reaches zero the vehicle will not start again until the system is refilled and, on some vehicles, reset with a tool - which is a much worse problem in a lay-by than on a driveway.
3. Look for white crystalline deposits around the injector, the pump and the pipe joints. Reductant crystallises when it leaks or when the system is not purged properly, and the deposits are unmistakable.
4. Inspect connectors underneath for corrosion and water.
5. In cold weather, consider freezing. Reductant freezes at around minus eleven degrees Celsius, and the system has heaters for exactly that reason - a failed heater looks like a supply fault.