Secondary Air Injection System Control "A" Circuit Low
P2257 indicates the engine control module detected a low voltage or open circuit condition in the secondary air injection (SAI) system control circuit A. This system injects fresh air into the exhaust manifold to reduce emissions during cold starts and warm-up, and the PCM cannot properly command the SAI pump motor due to this electrical fault.
What You Might Notice
- Secondary air injection system disabled or not operating
- Check engine light illuminated
- Peculiar noises from engine compartment
- Possible increase in exhaust emissions
- No obvious drivability symptoms in most cases
Most Common Causes
- 1
Blown fuse
The SAI system fuse may be blown, interrupting power to the control circuit. Check the fuse box for a burnt or open fuse related to the secondary air injection system.
- 2
Open or shorted control circuit wiring
The wiring harness controlling the SAI pump may have breaks, corrosion, or short circuits preventing proper voltage signal from the PCM to the pump motor.
- 3
Defective SAI pump motor
The secondary air injection pump motor itself may be internally shorted or open, preventing it from receiving and responding to the control signal from the PCM.
- 4
PCM programming error or defective PCM
The powertrain control module may have corrupted programming or an internal failure preventing it from generating the proper control signal to the SAI pump circuit.
How to Diagnose It
- 1
Check Blown fuse — The SAI system fuse may be blown, interrupting power to the control circuit. Check the fuse box for a burnt or open fuse related to the secondary air injection system.
- 2
Check Open or shorted control circuit wiring — The wiring harness controlling the SAI pump may have breaks, corrosion, or short circuits preventing proper voltage signal from the PCM to the pump motor.
- 3
Check Defective SAI pump motor — The secondary air injection pump motor itself may be internally shorted or open, preventing it from receiving and responding to the control signal from the PCM.
- 4
Check PCM programming error or defective PCM — The powertrain control module may have corrupted programming or an internal failure preventing it from generating the proper control signal to the SAI pump circuit.
How to Fix It
- 1
Replace blown fuse
Locate the secondary air injection system fuse in the vehicle's fuse box using the owner's manual or fuse diagram. Replace the blown fuse with one rated for the correct amperage.
- 2
Inspect and repair wiring harness
Use a DVOM to test continuity and voltage along the SAI control circuit wiring. Repair any damaged insulation, corrosion, or loose connections; replace the harness section if multiple defects are found.
- 3
Replace secondary air injection pump motor
If wiring tests good but the pump does not respond to power, the pump motor is likely defective. Disconnect the pump assembly and replace it with a new or remanufactured unit.
- 4
Reprogram or replace PCM
If all electrical components test good, the PCM may have corrupted programming or be internally defective. Contact a dealership or qualified technician for PCM reprogramming or replacement.
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