P0418
Fix within 1-2 weeksThe engine computer detected an electrical problem with the relay that controls the secondary air injection pump.
Code P0418 means the secondary air injection system relay circuit has an electrical fault. Common causes: Faulty relay (50%), wiring issues (25%), bad air pump (20%). Drivability: Yes, safe to drive. Repair cost: $25-$400 DIY, $150-$800 professional.
Can I Drive With P0418?
Yes, safe to drive
No restrictions
Stop driving immediately if: No need to stop driving unless other, more severe symptoms develop (e.g., engine overheating, significant power loss, loud noises).
Symptoms of P0418
- 1Check Engine Light is on
- 2No noticeable symptoms during driving
- 3Failed emissions inspection
- 4Secondary air pump runs constantly (rare, but possible if relay sticks)
Common Causes of P0418
Parts most likely causing this code, ranked by probability
A faulty relay is the most direct cause, as the code specifically points to an electrical malfunction in its circuit.
50% of P0418 cases are fixed by replacing this part
Corroded, loose, or damaged wiring and connectors to the relay or the secondary air pump can disrupt the circuit.
25% of P0418 cases are fixed by repairing wiring or connectors
An internal short or failure within the air pump can overload and damage the relay or its circuit.
20% of P0418 cases are fixed by replacing this part
A blown fuse protecting the secondary air injection system's relay or pump circuit will cause this code.
5% of P0418 cases are fixed by replacing this part
Check These First (Before Buying Parts)
- Check the fuse for the secondary air injection system in your vehicle's fuse box. A blown fuse is a quick and cheap fix.
- Visually inspect the secondary air injection pump relay and its connector for any signs of corrosion, burning, or loose connections.
How to Diagnose P0418
- 1Check the fuse for the secondary air injection system (consult your vehicle's owner's manual for location).
- 2Locate the secondary air injection pump relay and inspect its connections for corrosion or damage.
- 3Test the secondary air injection pump relay using a multimeter or by swapping it with a known good, identical relay (if available and safe to do so).
- 4Inspect the wiring harness leading to the secondary air pump and its relay for any visible damage, chafing, or corrosion.
- 5If the relay and wiring appear good, test the secondary air injection pump for proper operation (e.g., apply direct power and ground to see if it runs).
P0418 on Popular Vehicles
Chevrolet Silverado
2007-2024Silverado trucks, along with other GM vehicles, frequently experience secondary air injection pump failures. A seized pump can cause the P0418 code by overloading the relay circuit. Always check the pump for proper operation if the relay and fuse are good.
60% fixed by replacing the pump or relay
Ford F-150
2004-2024Ford F-150s can also see P0418 due to issues with the secondary air injection pump or its relay. Corrosion in the electrical connectors, especially those exposed to road salt or moisture, is a common contributing factor.
55% fixed by replacing the relay or repairing wiring
Honda Accord
2003-2024While less common than on trucks, P0418 on a Honda Accord often points directly to a faulty secondary air injection pump relay. Inspecting the relay and its fuse is the first step, followed by checking the pump if the relay is confirmed good.
70% fixed by replacing the relay or fuse
Frequently Asked Questions
What does P0418 mean?
P0418 indicates that your vehicle's engine computer has detected an electrical malfunction in the circuit for the secondary air injection system's 'A' relay. This system helps reduce emissions during cold starts.
Can I drive with P0418?
Yes, you can drive safely with a P0418 code. This code relates to an emissions system that primarily operates during cold starts and does not directly affect engine performance or safety. However, you will fail an emissions test.
Will P0418 clear itself?
No, P0418 will not clear itself. The underlying electrical fault needs to be diagnosed and repaired. Once the repair is made, you will need to clear the code with an OBD-II scanner, or it will clear after several drive cycles if the fault is resolved.
How do I fix P0418 myself?
To fix P0418 yourself, start by checking the fuse for the secondary air injection system. Next, locate and test the secondary air injection pump relay. If the relay is faulty, replace it. Also, inspect the wiring and connectors for any damage or corrosion. If the relay and wiring are good, you may need to test or replace the secondary air injection pump itself.
How much does it cost to fix P0418?
The cost to fix P0418 varies. DIY costs range from $25 for a fuse or relay to $400 for a new secondary air pump. Professional repair costs typically range from $150 to $800, including diagnosis and parts, depending on what component needs replacement.
P0418 keeps coming back - why?
If P0418 keeps coming back, it means the root cause was not fully addressed. Common reasons for recurrence include a faulty secondary air pump that damaged the new relay, intermittent wiring issues that were missed, or a problem with the engine computer (PCM) itself, though PCM failure is rare for this code.
Will P0418 fail emissions/smog test?
Yes, P0418 will cause your vehicle to fail an emissions or smog test. The secondary air injection system is a critical component of the vehicle's emissions control, and a fault in its circuit will prevent it from passing.
What's the difference between P0418 and P0410?
P0418 specifically indicates an electrical circuit malfunction with the secondary air injection system's 'A' relay. P0410, on the other hand, indicates a general malfunction in the secondary air injection system itself, meaning the system is not performing as expected, which could be due to a pump, valve, or hose issue, not necessarily the relay circuit.
P0418 on Chevrolet Silverado
On Chevrolet Silverado trucks, P0418 is often linked to a failing secondary air injection pump. These pumps are known to seize or draw excessive current, which can then blow the fuse or damage the relay. Always check the pump's operation if the relay and fuse are good.
Questions to Ask Your Mechanic
Did you check the fuse for the secondary air injection system?
Good answer: Yes, I checked the fuse, and it's good. Or, 'No, I found the fuse blown and replaced it, but the code returned, so I'm looking deeper.'
What did you find when testing the secondary air injection pump relay?
Good answer: I tested the relay for continuity and resistance, and it's either faulty or operating correctly. Or, 'I swapped it with a known good relay, and the code persisted.'
Did you inspect the wiring and connectors to the air pump and relay for corrosion or damage?
Good answer: Yes, I visually inspected the harness and checked for voltage drops across the circuit. Everything looks solid, or I found some corrosion and cleaned/repaired it.
Repair Cost Estimate
DIY Repair
Parts only
$25-$400
Shop Repair
Parts + labor
$150-$800
Save $125-$400 by doing it yourself
Difficulty
intermediate
Time
0.5-2 hours
Intermediate - While checking fuses and relays is beginner-friendly, diagnosing wiring issues or testing the air pump requires a multimeter and some electrical diagnostic knowledge.
Cost of Waiting
Ignoring P0418 will cause your vehicle to fail emissions inspections. While it doesn't immediately damage the engine, a faulty secondary air pump that caused the relay issue could eventually seize completely, requiring a more complex repair. A simple $50 relay fix now prevents a failed inspection and potential further electrical issues.
While You're In There...
Applying dielectric grease to electrical connectors, especially for the relay and pump, helps prevent corrosion and ensures a good electrical connection, which is crucial for this code.
Tools You'll Need
- OBD-II scanner
- Multimeter
- Basic hand tools (screwdrivers, wrenches)
- Test light (optional)
- Wire strippers/crimpers (if wiring repair is needed)
P0418 is a common emissions code that rarely indicates a serious engine problem. Most repairs are straightforward and involve replacing an inexpensive electrical component, getting your vehicle back to normal quickly.
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Your Next Steps
Step 1: Check the fuse for the secondary air injection system. Replace it if it's blown. If it blows again, there's a short circuit.
Step 2: If the fuse is good, locate the secondary air injection pump relay. Test it with a multimeter or swap it with a known good, identical relay from a non-critical system (like the horn relay, if compatible).
Step 3: If the relay is good, inspect the wiring harness and connectors leading to the relay and the secondary air pump for any damage, fraying, or corrosion. Repair any damaged wiring. Parts you'll likely need: Secondary Air Injection Pump Relay, or a new Secondary Air Injection Pump if the old one is seized.