A vehicle with an Air Injection Reaction (AIR) pump system has a 'Check Engine' light illuminated and DTC P0410 (Secondary Air Injection System Malfunction) stored. Upon inspection, the technician finds the AIR pump is running continuously, even after the engine has warmed up and during highway driving. What is the most likely cause?
- AA clogged catalytic converter
- BA faulty upstream oxygen sensor
- CA shorted AIR pump relay
- DA seized AIR pump motor
Show answer & explanationAnswer & explanation
Correct answer: C. A shorted AIR pump relay
DTC P0410 indicates a malfunction in the secondary air injection system. If the AIR pump is running continuously, even when not commanded (e.g., after warm-up or during highway driving), it suggests that the power supply to the pump is not being properly controlled. A shorted AIR pump relay would cause power to be continuously supplied to the pump motor, leading to its continuous operation. A seized pump would prevent it from running at all, and other options are unrelated to continuous pump operation.
Why the other options are wrong
- A. A clogged catalytic converter would primarily cause P0420 or driveability issues, not continuous AIR pump operation.
- B. A faulty upstream oxygen sensor would affect fuel trim and other emissions, but not directly cause the AIR pump to run continuously.
- D. A seized AIR pump motor would prevent the pump from running, not cause it to run continuously.
AIR Pump Continuous Operation
The secondary air injection pump running constantly, regardless of engine conditions, often due to an electrical fault in its control circuit.
- Typically caused by a shorted relay, preventing the ECM from cycling the pump off.
- Leads to premature pump wear and can cause other issues.
- Usually associated with P0410 DTC.
Memory trick: Pump won't stop? The relay's stuck on, sending power non-stop!