Secondary Air Injection System Control "B" Circuit Low
P2259 indicates a problem with the Secondary Air Injection (SAI) System Control B circuit, which monitors voltage in the control circuit for the secondary air pump. The system is detecting a low voltage condition that prevents proper operation of the secondary air injection pump motor or its control circuit.
What You Might Notice
- Secondary air injection system disabled or not functioning
- Check engine light illuminated
- Peculiar noises from engine compartment
- Failed emissions test
- Reduced fuel economy
Most Common Causes
- 1
Blown fuse
A blown fuse in the secondary air injection circuit prevents voltage from reaching the pump motor control circuit. Check the fuse box for a burned or open fuse related to the SAI system.
- 2
Open or shorted control wiring
Wiring harness damage, corrosion, or loose connectors in the SAI control circuit can cause voltage drops or complete circuit failure. Inspect all related wiring for damage or poor connections.
- 3
Defective secondary air pump motor
The pump motor itself may be failing or seized, causing excessive current draw or an open circuit condition. A faulty motor will prevent the system from operating even with proper voltage supply.
- 4
PCM or programming error
A defective powertrain control module or corrupted PCM programming can fail to properly control the secondary air injection circuit. This may require PCM reprogramming or replacement.
How to Diagnose It
- 1
Check Blown fuse — A blown fuse in the secondary air injection circuit prevents voltage from reaching the pump motor control circuit. Check the fuse box for a burned or open fuse related to the SAI system.
- 2
Check Open or shorted control wiring — Wiring harness damage, corrosion, or loose connectors in the SAI control circuit can cause voltage drops or complete circuit failure. Inspect all related wiring for damage or poor connections.
- 3
Check Defective secondary air pump motor — The pump motor itself may be failing or seized, causing excessive current draw or an open circuit condition. A faulty motor will prevent the system from operating even with proper voltage supply.
- 4
Check PCM or programming error — A defective powertrain control module or corrupted PCM programming can fail to properly control the secondary air injection circuit. This may require PCM reprogramming or replacement.
How to Fix It
- 1
Check and replace fuses
Locate the fuse box and inspect the secondary air injection system fuse. If blown, replace with the correct amperage fuse specified in your owner's manual. Retest after replacement.
- 2
Inspect and repair wiring
Using a multimeter, test the control circuit for continuity and voltage. Repair or replace any damaged wiring, connectors, or grounds in the secondary air injection control circuit.
- 3
Replace secondary air pump motor
If voltage is present at the pump connector but the motor is not operating, the pump motor is likely defective and must be replaced. Install the new pump and verify system operation.
- 4
Reprogram or replace PCM
If all circuits test normal but the code persists, the PCM may have a software issue or internal failure. Contact a dealership for reprogramming or obtain a replacement PCM module.
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