Secondary Air Injection System Control Circuit Low
The P2259 code indicates that the Powertrain Control Module (PCM) has detected a low voltage condition in the control circuit of the secondary air injection (SAI) system. The SAI system pumps fresh air into the exhaust manifold during cold starts to reduce emissions. A low circuit voltage typically points to a faulty relay, blown fuse, damaged wiring, or a defective SAI pump. This can prevent the system from operating, leading to increased emissions and potential drivability issues.
1. Most Common Causes
- Blown fuse or faulty relay for the SAI system
- Damaged, corroded, or shorted wiring/connectors in the control circuit
- Failed secondary air injection pump
- Faulty PCM (rare)
2. Symptoms You Will Notice
- Illuminated Check Engine Light
- Failed emissions test due to increased cold start emissions
- Possible rough idle or hesitation during cold start
- No audible air pump operation on cold start
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for related codes (e.g., P0410, P0411).
Step 2: Visually inspect the SAI pump fuse and relay; replace if blown or faulty.
Step 3: Check the wiring and connectors between the PCM and SAI pump for damage, corrosion, or shorts.
Step 4: Test the SAI pump by applying battery voltage directly; if it doesn't run, replace the pump.
Step 5: If all else passes, test the PCM output signal to the SAI pump control circuit; if missing, consider PCM replacement.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, it is generally safe to drive, but the vehicle may fail an emissions test and the Check Engine Light will stay on. The SAI system only operates during cold starts, so drivability is usually unaffected.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts like a fuse, relay, or wiring repair. If the SAI pump needs replacement, it can cost $200-$500 including labor.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.