What Does P1661 Mean?
The idle air control (IAC) system diagnostics have been disabled because the power steering pressure (PSP) switch is stuck in the ON position. The PCM cannot properly test IAC operation when it continuously receives a signal indicating high power steering load.
Common Causes
40%
Failed power steering pressure switch stuck closed/ON
25%
Short to ground in PSP switch circuit wiring
20%
Corroded or damaged PSP switch connector causing false signal
10%
Contaminated power steering fluid causing switch malfunction
5%
PCM input circuit failure reading PSP switch incorrectly
Diagnostic Steps
1
Step 1: Monitor PSP switch status with scan tool in live data with engine running and wheels straight
2
Step 2: Disconnect PSP switch connector and observe if switch status changes (should read OFF)
3
Step 3: Test PSP switch operation with multimeter by turning steering wheel and checking continuity changes
4
Step 4: Check PSP switch circuit wiring for shorts to ground between switch and PCM
5
Step 5: Inspect power steering system for proper fluid level, contamination, and correct pressure operation
Estimated Repair Cost
$100 - $350
Parts + labor, varies by vehicle and location
The idle air control (IAC) system diagnostics have been disabled because the power steering pressure (PSP) switch is stuck in the ON position. The PCM cannot properly test IAC operation when it continuously receives a signal indicating high power steering load.
The most common cause of P1661 (IAC Monitor Disabled by PSP Switch Failed On) is: Failed power steering pressure switch stuck closed/ON
Typical repair costs for P1661 range from $100 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Idle quality may be slightly affected, particularly during power steering use. IAC monitoring is disabled but system still functions. No significant safety concern.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1661 to identify the root cause.
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Quick Info
Category
Powertrain
System
Idle Control System
Difficulty
Type
Manufacturer
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