🚨 Diagnostic Profile
Vehicle/Equipment Make: BUICK
Technical Description: Secondary Air Injection System Relay A Control Circuit High
This diagnostic trouble code indicates that the Powertrain Control Module (PCM) has detected a voltage signal higher than expected on the control circuit for the Secondary Air Injection (AIR) System Relay A. The secondary air injection system is responsible for pumping fresh air into the exhaust stream during cold starts to help the catalytic converter reach operating temperature faster, reducing cold-start emissions. A ‘control circuit high’ fault typically points to a short to voltage, a stuck-open relay, or an internal PCM driver issue affecting the relay’s commanded state.
🚨 Repair Difficulty Tier
Difficulty Rating: Intermediate
This repair requires a digital multimeter and a capable OBD-II scan tool with live data streaming and bi-directional control capability to properly diagnose the relay circuit. While no specialized module programming is typically required, the diagnosis involves tracing wiring harnesses, testing relay continuity, and verifying PCM driver output — tasks that go beyond basic hand-tool repairs but do not reach the complexity of airbag or CAN bus module flashing work.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin with a visual inspection of the Secondary Air Injection relay, located in the underhood fuse/relay block (verify exact location using the vehicle’s fuse box diagram). Check for:
• Corrosion, burnt contacts, or melted relay socket pins
• Damaged, frayed, or chafed wiring near the relay and AIR pump motor
• Loose or corroded ground connections related to the AIR system
• Signs of water intrusion in the relay box
Also inspect the Secondary Air Injection pump and associated vacuum/air hoses for physical damage, disconnection, or blockage.
Step 2: Diagnostic Verification
Connect an OBD-II scan tool and confirm the exact code and freeze frame data. Using live data mode, command the AIR relay ON and OFF (if bi-directional control is supported) while monitoring the control circuit voltage.
With the key on, engine off, use a digital multimeter to back-probe the relay control circuit wire at the connector:
• A reading close to battery voltage (12V) when the relay should be OFF confirms a ‘control circuit high’ short to voltage.
• Check for continuity and resistance across the relay coil terminals to rule out an internally shorted relay.
• Inspect the PCM connector and pin for the AIR relay driver circuit for corrosion or damage.
• Test circuit resistance between the relay connector and the PCM to rule out chafed wiring shorting to a power source.
Step 3: Resolution & Reset Process
If the relay itself tests faulty (stuck contacts or shorted coil), replace the Secondary Air Injection relay with an OEM-specified part. If wiring is found shorted to a voltage source, repair or replace the damaged harness section and properly insulate the repair.
If the relay and wiring test normal, further inspection of the PCM driver circuit may be required, as an internal PCM fault can occasionally cause this code (rare, but possible).
After repairs, clear the DTC using the scan tool, cycle the ignition, and run the vehicle through several cold-start cycles to confirm the AIR system activates correctly and the code does not return. Perform a drive cycle if required by the scan tool to confirm full system readiness.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Secondary Air Injection Relay, wiring harness repair kit (if needed), OBD-II scan tool with bi-directional control, digital multimeter.
Average Component Price: $15 – $45 for the relay itself; $50 – $150 if harness repair is required; no special dealer software programming is typically necessary for this repair.
Estimated Labor Hours: 0.5 – 1.5 hours for diagnosis and relay replacement; up to 2.5 hours if wiring harness repair is needed.