Secondary Air Injection System Relay "B" Circuit Malfunction
The Secondary Air Injection (SAI) system relay B is not functioning properly, preventing the SAI pump from activating when needed. This system reduces exhaust emissions during cold start and idle conditions but is not critical for engine operation.
What You Might Notice
- No symptoms may be noticeable to the driver
- SAI pump does not activate
- Check engine light illuminated
- Failed emissions test
- Slightly elevated cold-start emissions
Most Common Causes
- 1
Defective SAI pump relay
The relay controlling the SAI pump has failed internally and cannot switch the pump circuit on or off properly.
- 2
Blown SAI system fuses
One or more fuses in the SAI system circuit have blown, cutting power to the relay or pump circuit.
- 3
Shorted wiring or connectors
Damaged insulation, corrosion, or loose connections in the SAI relay circuit are preventing proper electrical signal transmission.
- 4
Defective SAI pump
The secondary air injection pump itself may have failed, causing the relay to not energize or drawing excessive current that trips the circuit.
How to Diagnose It
- 1
Check Defective SAI pump relay — The relay controlling the SAI pump has failed internally and cannot switch the pump circuit on or off properly.
- 2
Check Blown SAI system fuses — One or more fuses in the SAI system circuit have blown, cutting power to the relay or pump circuit.
- 3
Check Shorted wiring or connectors — Damaged insulation, corrosion, or loose connections in the SAI relay circuit are preventing proper electrical signal transmission.
- 4
Check Defective SAI pump — The secondary air injection pump itself may have failed, causing the relay to not energize or drawing excessive current that trips the circuit.
How to Fix It
- 1
Replace SAI pump relay
Locate the SAI relay in the fuse/relay box (consult your vehicle's service manual for location) and replace it with an OEM or quality aftermarket relay rated for your vehicle.
- 2
Check and replace blown fuses
Inspect the SAI system fuses in the main fuse box and any auxiliary boxes. Replace any blown fuses with the correct amperage rating specified in your owner's manual.
- 3
Inspect and repair SAI wiring and connectors
Examine all SAI circuit wiring for damage, corrosion, or loose connections between the relay, pump, and ECU. Clean corroded connectors, repair damaged wiring, or replace connector assemblies as needed.
- 4
Replace SAI pump if defective
If relay and wiring are confirmed good, the SAI pump itself may be faulty. Remove and replace the pump assembly following your vehicle's service manual procedures.
Need a deeper diagnosis?
Search for related repair guides or browse by system.