What Does P1421 Mean?
The PCM has detected that the Secondary Air Injection valve control circuit is shorted to ground. This prevents proper operation of the SAI valve that directs air into the exhaust system.
Common Causes
35%
Chafed or damaged wiring harness grounding out on metal
30%
Failed SAI valve solenoid with internal short to ground
20%
Corroded connector causing cross-circuit short
15%
Water intrusion in valve or connector causing short
Diagnostic Steps
1
Step 1: Disconnect SAI valve connector and check for resistance between valve control circuit and ground - should read infinite resistance
2
Step 2: Inspect wiring harness from PCM to valve for damage, paying attention to areas where harness passes near sharp edges or heat sources
3
Step 3: With valve disconnected, test resistance of control wire from PCM side - should show infinite resistance to ground
4
Step 4: Measure resistance across SAI valve solenoid terminals - compare to specifications (typically 20-50 ohms)
5
Step 5: If wiring is intact, replace SAI valve and retest circuit
Estimated Repair Cost
$150 - $500
Parts + labor, varies by vehicle and location
The PCM has detected that the Secondary Air Injection valve control circuit is shorted to ground. This prevents proper operation of the SAI valve that directs air into the exhaust system.
The most common cause of P1421 (Secondary Air Injection Valve Circuit Short To Ground) is: Chafed or damaged wiring harness grounding out on metal
Typical repair costs for P1421 range from $150 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to operate normally. This only affects emissions system performance during cold starts and will not impact driving safety or performance.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1421 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control - Secondary Air Injection
Difficulty
Type
Manufacturer
Recommended Tools
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